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671 lines
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671 lines
228 KiB
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class=tag-list-link href=/tags/Spring/ rel=tag>Spring</a><span class=tag-list-count>7</span><li class=tag-list-item><a class=tag-list-link href=/tags/Spring-Event/ rel=tag>Spring Event</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/SpringBoot/ rel=tag>SpringBoot</a><span class=tag-list-count>15</span><li class=tag-list-item><a class=tag-list-link href=/tags/Sql%E6%B3%A8%E5%85%A5/ rel=tag>Sql注入</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Stream/ rel=tag>Stream</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Synchronized/ rel=tag>Synchronized</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/Thread-dump/ rel=tag>Thread dump</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/ThreadLocal/ rel=tag>ThreadLocal</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/ThreadPool/ rel=tag>ThreadPool</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Tomcat/ rel=tag>Tomcat</a><span class=tag-list-count>6</span><li class=tag-list-item><a class=tag-list-link href=/tags/Trapping-Rain-Water/ rel=tag>Trapping Rain Water</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/WeakReference/ rel=tag>WeakReference</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Web/ rel=tag>Web</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Webhook/ rel=tag>Webhook</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/Windows/ rel=tag>Windows</a><span class=tag-list-count>4</span><li class=tag-list-item><a class=tag-list-link href=/tags/WordPress/ rel=tag>WordPress</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/aqs/ rel=tag>aqs</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/await/ rel=tag>await</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/bloom-filter/ rel=tag>bloom filter</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/c/ rel=tag>c++</a><span class=tag-list-count>14</span><li class=tag-list-item><a class=tag-list-link href=/tags/cglib/ rel=tag>cglib</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/cgroup/ rel=tag>cgroup</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/cluster/ rel=tag>cluster</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/condition/ rel=tag>condition</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/dnsmasq/ rel=tag>dnsmasq</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/docker/ rel=tag>docker</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/dp/ rel=tag>dp</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/dubbo/ rel=tag>dubbo</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/echo/ rel=tag>echo</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/environment/ rel=tag>environment</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/gap-lock/ rel=tag>gap lock</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/gc/ rel=tag>gc</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/git/ rel=tag>git</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/grep/ rel=tag>grep</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/hadoop/ rel=tag>hadoop</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/headscale/ rel=tag>headscale</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/hexo/ rel=tag>hexo</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/icu4c/ rel=tag>icu4c</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/im/ rel=tag>im</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/is-not-null/ rel=tag>is not null</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/is-null/ rel=tag>is null</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/j-u-c/ rel=tag>j.u.c</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/java/ rel=tag>java</a><span class=tag-list-count>35</span><li class=tag-list-item><a class=tag-list-link href=/tags/jvm/ rel=tag>jvm</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/leetcode/ rel=tag>leetcode</a><span class=tag-list-count>40</span><li class=tag-list-item><a class=tag-list-link href=/tags/leetcode-155/ rel=tag>leetcode 155</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/linked-list/ rel=tag>linked list</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/linux/ rel=tag>linux</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/lock/ rel=tag>lock</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/mfc/ rel=tag>mfc</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/min-stack/ rel=tag>min stack</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/mq/ rel=tag>mq</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/mvcc/ rel=tag>mvcc</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/mysql/ rel=tag>mysql</a><span class=tag-list-count>6</span><li class=tag-list-item><a class=tag-list-link href=/tags/namespace/ rel=tag>namespace</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/nas/ rel=tag>nas</a><span class=tag-list-count>6</span><li class=tag-list-item><a class=tag-list-link href=/tags/next-key-lock/ rel=tag>next-key lock</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/nginx/ rel=tag>nginx</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/nullsfirst/ rel=tag>nullsfirst</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/openresty/ rel=tag>openresty</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/php/ rel=tag>php</a><span class=tag-list-count>4</span><li class=tag-list-item><a class=tag-list-link href=/tags/powershell/ rel=tag>powershell</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/procedure/ rel=tag>procedure</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/python/ rel=tag>python</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/read-view/ rel=tag>read view</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/redis/ rel=tag>redis</a><span class=tag-list-count>12</span><li class=tag-list-item><a class=tag-list-link href=/tags/scp/ rel=tag>scp</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/signal/ rel=tag>signal</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/sort/ rel=tag>sort</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/spark/ rel=tag>spark</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/ssh/ rel=tag>ssh</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/stack/ rel=tag>stack</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/stream/ rel=tag>stream</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/string/ rel=tag>string</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/swoole/ rel=tag>swoole</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/top/ rel=tag>top</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/uname/ rel=tag>uname</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/unlock/ rel=tag>unlock</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/utf8/ rel=tag>utf8</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/utf8mb4/ rel=tag>utf8mb4</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/utf8mb4-0900-ai-ci/ rel=tag>utf8mb4_0900_ai_ci</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/utf8mb4-general-ci/ rel=tag>utf8mb4_general_ci</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/utf8mb4-unicode-ci/ rel=tag>utf8mb4_unicode_ci</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/value/ rel=tag>value</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/websocket/ rel=tag>websocket</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/windows/ rel=tag>windows</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/wsl/ rel=tag>wsl</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/zookeeper/ rel=tag>zookeeper</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/zsh/ rel=tag>zsh</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%89%E9%98%B6%E6%AE%B5%E6%8F%90%E4%BA%A4/ rel=tag>三阶段提交</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%8D%E5%8F%AF%E5%8F%98%E5%BC%95%E7%94%A8/ rel=tag>不可变引用</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%9C%E4%BA%AC%E5%A5%A5%E8%BF%90%E4%BC%9A/ rel=tag>东京奥运会</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%A4%E9%98%B6%E6%AE%B5%E6%8F%90%E4%BA%A4/ rel=tag>两阶段提交</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%AD%E5%B1%B1%E8%B7%AF/ rel=tag>中山路</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%AD%E5%BA%8F/ rel=tag>中序</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%AD%E9%97%B4%E4%BB%B6/ rel=tag>中间件</a><span class=tag-list-count>4</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B8%BE%E9%87%8D/ rel=tag>举重</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%B9%92%E4%B9%93%E7%90%83/ rel=tag>乒乓球</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%BA%8B%E5%8A%A1/ rel=tag>事务</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%BA%8C%E5%8F%89%E6%A0%91/ rel=tag>二叉树</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%BA%92%E6%96%A5%E9%94%81/ rel=tag>互斥锁</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%BB%A3%E7%A0%81%E9%A2%98%E8%A7%A3/ rel=tag>代码题解</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E4%BF%AE%E7%94%B5%E8%84%91%E7%9A%84/ rel=tag>修电脑的</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%81%8F%E5%90%91%E9%94%81/ rel=tag>偏向锁</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%81%A5%E5%BA%B7%E7%A0%81/ rel=tag>健康码</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%85%AC%E4%BA%A4/ rel=tag>公交</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%85%AC%E4%BA%A4%E8%BD%A6/ rel=tag>公交车</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%86%85%E5%AD%98%E5%88%86%E5%B8%83/ rel=tag>内存分布</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%86%85%E5%AD%98%E6%B3%84%E6%BC%8F/ rel=tag>内存泄漏</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%87%86%E5%A4%87/ rel=tag>准备</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%87%8F%E8%82%A5/ rel=tag>减肥</a><span class=tag-list-count>7</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E4%BA%8B%E5%8A%A1/ rel=tag>分布式事务</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%88%86%E5%B8%83%E5%BC%8F%E9%94%81/ rel=tag>分布式锁</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%88%87%E7%89%87/ rel=tag>切片</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%88%9D%E5%A7%8B%E5%8C%96/ rel=tag>初始化</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%89%8A%E5%B3%B0%E5%A1%AB%E8%B0%B7/ rel=tag>削峰填谷</a><span class=tag-list-count>4</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%89%8D%E5%BA%8F/ rel=tag>前序</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8A%A0%E5%A1%9E/ rel=tag>加塞</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8A%A0%E8%BD%BD/ rel=tag>加载</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8D%95%E4%BE%8B/ rel=tag>单例</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8D%9A%E5%AE%A2%EF%BC%8C%E6%96%87%E7%AB%A0/ rel=tag>博客，文章</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8E%A6%E9%97%A8/ rel=tag>厦门</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8F%8C%E4%BA%B2%E5%A7%94%E6%B4%BE/ rel=tag>双亲委派</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8F%91%E8%A1%8C%E7%89%88/ rel=tag>发行版</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8F%A3%E7%BD%A9/ rel=tag>口罩</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%8F%AF%E5%8F%98%E5%BC%95%E7%94%A8/ rel=tag>可变引用</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%90%90%E6%A7%BD/ rel=tag>吐槽</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%9B%A4%E7%89%A9%E8%B5%84/ rel=tag>囤物资</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%9E%83%E5%9C%BE%E5%9B%9E%E6%94%B6/ rel=tag>垃圾回收</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%9F%BA%E7%A1%80%E8%AE%BE%E6%96%BD/ rel=tag>基础设施</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%A4%A7%E6%89%AB%E9%99%A4/ rel=tag>大扫除</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E5%AD%97%E7%AC%A6%E9%9B%86/ rel=tag>字符集</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link 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href=/tags/%E6%8D%A2%E8%BD%A6%E7%89%8C/ rel=tag>换车牌</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%8E%92%E5%BA%8F/ rel=tag>排序</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%8E%A5%E9%9B%A8%E6%B0%B4/ rel=tag>接雨水</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%95%B0%E6%8D%AE%E6%BA%90%E5%8A%A8%E6%80%81%E5%88%87%E6%8D%A2/ rel=tag>数据源动态切换</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%95%B0%E6%8D%AE%E7%BB%93%E6%9E%84/ rel=tag>数据结构</a><span class=tag-list-count>11</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%96%B0%E8%AF%AD%E8%A8%80/ rel=tag>新语言</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E6%97%85%E6%B8%B8/ rel=tag>旅游</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link 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class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%94%9F%E6%B4%BB/ rel=tag>生活</a><span class=tag-list-count>42</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%94%B5%E7%93%B6%E8%BD%A6/ rel=tag>电瓶车</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%96%AB%E6%83%85/ rel=tag>疫情</a><span class=tag-list-count>2</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%9C%8B%E4%B9%A6/ rel=tag>看书</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%9C%8B%E5%89%A7/ rel=tag>看剧</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%9F%A9%E9%98%B5/ rel=tag>矩阵</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%AB%AF%E5%8F%A3%E8%BD%AC%E5%8F%91/ rel=tag>端口转发</a><span class=tag-list-count>3</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%B1%BB%E5%8A%A0%E8%BD%BD/ rel=tag>类加载</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%B3%9F%E5%BF%83%E4%BA%8B/ rel=tag>糟心事</a><span class=tag-list-count>5</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%B4%A2%E5%BC%95/ rel=tag>索引</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%BA%BF%E7%A8%8B%E6%B1%A0/ rel=tag>线程池</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%BC%93%E5%AD%98/ rel=tag>缓存</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF/ rel=tag>缓存击穿</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link href=/tags/%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F/ rel=tag>缓存穿透</a><span class=tag-list-count>1</span><li class=tag-list-item><a class=tag-list-link 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title=https://covermusic.cn>69伙伴</a></ul></div></div></aside></div><div class="main-inner index posts-expand"><div class=post-block><article class=post-content itemscope itemtype=http://schema.org/Article><link href=https://nicksxs.me/2021/03/14/Leetcode-121-%E4%B9%B0%E5%8D%96%E8%82%A1%E7%A5%A8%E7%9A%84%E6%9C%80%E4%BD%B3%E6%97%B6%E6%9C%BA-Best-Time-to-Buy-and-Sell-Stock-%E9%A2%98%E8%A7%A3%E5%88%86%E6%9E%90/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="learn from zero,技术博客，Nicksxs，史学森" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="undefined | Nicksxs's Blog" itemprop=name><meta itemprop=description></span><header class=post-header><h2 itemprop="name headline" class=post-title><a class=post-title-link href=/2021/03/14/Leetcode-121-%E4%B9%B0%E5%8D%96%E8%82%A1%E7%A5%A8%E7%9A%84%E6%9C%80%E4%BD%B3%E6%97%B6%E6%9C%BA-Best-Time-to-Buy-and-Sell-Stock-%E9%A2%98%E8%A7%A3%E5%88%86%E6%9E%90/ itemprop=url>Leetcode 121 买卖股票的最佳时机(Best Time to Buy and Sell Stock) 题解分析</a></h2><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间：2021-03-14 22:34:30" datetime=2021-03-14T22:34:30+08:00>2021-03-14</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/ itemprop=url rel=index><span itemprop=name>Java</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/leetcode/ itemprop=url rel=index><span itemprop=name>leetcode</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/leetcode/java/ itemprop=url rel=index><span itemprop=name>java</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/DP/ itemprop=url rel=index><span itemprop=name>DP</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/leetcode/java/DP/ itemprop=url rel=index><span itemprop=name>DP</span></a> </span></span><span class="post-meta-item leancloud_visitors" data-flag-title="Leetcode 121 买卖股票的最佳时机(Best Time to Buy and Sell Stock) 题解分析" id=/2021/03/14/Leetcode-121-%E4%B9%B0%E5%8D%96%E8%82%A1%E7%A5%A8%E7%9A%84%E6%9C%80%E4%BD%B3%E6%97%B6%E6%9C%BA-Best-Time-to-Buy-and-Sell-Stock-%E9%A2%98%E8%A7%A3%E5%88%86%E6%9E%90/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数：</span> <span class=leancloud-visitors-count></span> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-comment"></i> </span><span class=post-meta-item-text>Disqus：</span> <a href=/2021/03/14/Leetcode-121-%E4%B9%B0%E5%8D%96%E8%82%A1%E7%A5%A8%E7%9A%84%E6%9C%80%E4%BD%B3%E6%97%B6%E6%9C%BA-Best-Time-to-Buy-and-Sell-Stock-%E9%A2%98%E8%A7%A3%E5%88%86%E6%9E%90/#disqus_thread itemprop=discussionUrl title=disqus><span class="post-comments-count disqus-comment-count" data-disqus-identifier=2021/03/14/Leetcode-121-买卖股票的最佳时机-Best-Time-to-Buy-and-Sell-Stock-题解分析/ itemprop=commentCount></span></a></span></div></div></header><div class=post-body itemprop=articleBody><h3 id=题目介绍><a class=headerlink href=#题目介绍 title=题目介绍></a>题目介绍</h3><p>You are given an array <code>prices</code> where <code>prices[i]</code> is the price of a given stock on the i<sup>th</sup> day.<p>You want to maximize your profit by choosing a <strong>single day</strong> to buy one stock and choosing a <strong>different day in the future</strong> to sell that stock.<p>Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return <code>0</code>.<p>给定一个数组 <code>prices</code> ，它的第 <code>i</code> 个元素 <code>prices[i]</code> 表示一支给定股票第 <code>i</code> 天的价格。<p>你只能选择 <strong>某一天</strong> 买入这只股票，并选择在 <strong>未来的某一个不同的日子</strong> 卖出该股票。设计一个算法来计算你所能获取的最大利润。<p>返回你可以从这笔交易中获取的最大利润。如果你不能获取任何利润，返回 <code>0</code> 。<h3 id=简单分析><a class=headerlink href=#简单分析 title=简单分析></a>简单分析</h3><p>其实这个跟二叉树的最长路径和有点类似，需要找到整体的最大收益，但是在迭代过程中需要一个当前的值<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token keyword">int</span> maxSofar <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
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<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">maxProfit</span><span class="token punctuation">(</span><span class="token keyword">int</span><span class="token punctuation">[</span><span class="token punctuation">]</span> prices<span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span>prices<span class="token punctuation">.</span>length <span class="token operator"><=</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token keyword">int</span> maxIn <span class="token operator">=</span> prices<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token keyword">int</span> maxOut <span class="token operator">=</span> prices<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span> i <span class="token operator"><</span> prices<span class="token punctuation">.</span>length<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span>maxIn <span class="token operator">></span> prices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token comment">// 当循环当前值小于之前的买入值时就当成买入值，同时卖出也要更新</span>
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maxIn <span class="token operator">=</span> prices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span>
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maxOut <span class="token operator">=</span> prices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span>prices<span class="token punctuation">[</span>i<span class="token punctuation">]</span> <span class="token operator">></span> maxOut<span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token comment">// 表示一个可卖出点，即比买入值高时</span>
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maxOut <span class="token operator">=</span> prices<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token comment">// 需要设置一个历史值</span>
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maxSofar <span class="token operator">=</span> <span class="token class-name">Math</span><span class="token punctuation">.</span><span class="token function">max</span><span class="token punctuation">(</span>maxSofar<span class="token punctuation">,</span> maxOut <span class="token operator">-</span> maxIn<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span>
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<span class="token keyword">return</span> maxSofar<span class="token punctuation">;</span>
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<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><h3 id=总结下><a class=headerlink href=#总结下 title=总结下></a>总结下</h3><p>一开始看到 easy 就觉得是很简单，就没有 maxSofar ，但是一提交就出现问题了<br>对于<code>[2, 4, 1]</code>这种就会变成 0，所以还是需要一个历史值来存放历史最大值，这题有点动态规划的意思</div><footer class=post-footer><div class=post-eof></div></footer></article></div><div class=post-block><article class=post-content itemscope itemtype=http://schema.org/Article><link href=https://nicksxs.me/2021/03/07/%E3%80%8A%E5%9E%83%E5%9C%BE%E5%9B%9E%E6%94%B6%E7%AE%97%E6%B3%95%E6%89%8B%E5%86%8C%E8%AF%BB%E4%B9%A6%E3%80%8B%E7%AC%94%E8%AE%B0%E4%B9%8B%E6%95%B4%E7%90%86%E7%AE%97%E6%B3%95/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="learn from zero,技术博客，Nicksxs，史学森" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="undefined | Nicksxs's Blog" itemprop=name><meta itemprop=description></span><header class=post-header><h2 itemprop="name headline" class=post-title><a class=post-title-link href=/2021/03/07/%E3%80%8A%E5%9E%83%E5%9C%BE%E5%9B%9E%E6%94%B6%E7%AE%97%E6%B3%95%E6%89%8B%E5%86%8C%E8%AF%BB%E4%B9%A6%E3%80%8B%E7%AC%94%E8%AE%B0%E4%B9%8B%E6%95%B4%E7%90%86%E7%AE%97%E6%B3%95/ itemprop=url>《垃圾回收算法手册读书》笔记之整理算法</a></h2><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间：2021-03-07 20:37:06" datetime=2021-03-07T20:37:06+08:00>2021-03-07</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar-check"></i> </span><span class=post-meta-item-text>更新于</span> <time title="修改时间：2022-06-11 22:45:11" datetime=2022-06-11T22:45:11+08:00 itemprop=dateModified>2022-06-11</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/ itemprop=url rel=index><span itemprop=name>Java</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/gc/ itemprop=url rel=index><span itemprop=name>gc</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/gc/jvm/ itemprop=url rel=index><span itemprop=name>jvm</span></a> </span></span><span class="post-meta-item leancloud_visitors" data-flag-title=《垃圾回收算法手册读书》笔记之整理算法 id=/2021/03/07/%E3%80%8A%E5%9E%83%E5%9C%BE%E5%9B%9E%E6%94%B6%E7%AE%97%E6%B3%95%E6%89%8B%E5%86%8C%E8%AF%BB%E4%B9%A6%E3%80%8B%E7%AC%94%E8%AE%B0%E4%B9%8B%E6%95%B4%E7%90%86%E7%AE%97%E6%B3%95/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数：</span> <span class=leancloud-visitors-count></span> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-comment"></i> </span><span class=post-meta-item-text>Disqus：</span> <a href=/2021/03/07/%E3%80%8A%E5%9E%83%E5%9C%BE%E5%9B%9E%E6%94%B6%E7%AE%97%E6%B3%95%E6%89%8B%E5%86%8C%E8%AF%BB%E4%B9%A6%E3%80%8B%E7%AC%94%E8%AE%B0%E4%B9%8B%E6%95%B4%E7%90%86%E7%AE%97%E6%B3%95/#disqus_thread itemprop=discussionUrl title=disqus><span class="post-comments-count disqus-comment-count" data-disqus-identifier=2021/03/07/《垃圾回收算法手册读书》笔记之整理算法/ itemprop=commentCount></span></a></span></div></div></header><div class=post-body itemprop=articleBody><p>最近看了下这本垃圾回收算法手册，看到了第三章的标记-整理回收算法，做个简单的读书笔记<h3 id=双指针整理算法><a class=headerlink href=#双指针整理算法 title=双指针整理算法></a>双指针整理算法</h3><p>对于一块待整理区域，通过两个指针，free 在区域的起始端，scan 指针在区域的末端，free 指针从前往后知道找到空闲区域，scan 从后往前一直找到存活对象，当 free 指针未与 scan 指针交叉时，会给 scan 位置的对象特定位置标记上 free 的地址，即将要转移的地址，不过这里有个限制，这种整理算法一般会用于对象大小统一的情况，否则 free 指针扫描时还需要匹配scan 指针扫描到的存活对象的大小。<br><img data-src=https://img.nicksxs.com/uPic/yLQlgj.png><h3 id=Lisp-2-整理算法><a title="Lisp 2 整理算法" class=headerlink href=#Lisp-2-整理算法></a>Lisp 2 整理算法</h3><p>需要三次完整遍历堆区域<br>第一遍是遍历后将计算出所有对象的最终地址（转发地址）<br>第二遍是使用转发地址更新赋值器线程根以及被标记对象中的引用，该操作将确保它们指向对象的新位置<br>第三次遍历是relocate最终将存活对象移动到其新的目标位置<h3 id=引线整理算法><a class=headerlink href=#引线整理算法 title=引线整理算法></a>引线整理算法</h3><p>这个真的长见识了，<br><img data-src=https://img.nicksxs.com/uPic/6yeA7n.png><br>可以看到，原来是 A，B，C 对象引用了 N，这里会在第一次遍历的时候把这种引用反过来，让 N 的对象头部保存下 A 的地址，表示这类引用，然后在遍历到 B 的时候在链起来，到最后就会把所有引用了 N 对象的所有对象通过引线链起来，在第二次遍历的时候就把更新A，B，C 对象引用的 N 地址，并且移动 N 对象<h3 id=单次遍历算法><a class=headerlink href=#单次遍历算法 title=单次遍历算法></a>单次遍历算法</h3><p>这个一直提到过位图的实现方式，<br><img data-src=https://img.nicksxs.com/uPic/Jqtuzu.png><br>可以看到在第一步会先通过位图标记，标记的方式是位图的每一位对应的堆内存的一个字（这里可能指的是 byte 吧），然后将一个存活对象的内存区域的第一个字跟最后一个字标记，这里如果在通过普通的方式就还需要一个地方在存转发地址，但是因为具体的位置可以通过位图算出来，也就不需要额外记录了</div><footer class=post-footer><div class=post-eof></div></footer></article></div><div class=post-block><article class=post-content itemscope itemtype=http://schema.org/Article><link href=https://nicksxs.me/2021/02/28/%E9%97%B2%E8%81%8A%E4%B8%8B%E4%B9%98%E5%85%AC%E4%BA%A4%E7%9A%84%E7%94%A8%E6%88%B7%E4%BD%93%E9%AA%8C/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="learn from zero,技术博客，Nicksxs，史学森" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="undefined | Nicksxs's Blog" itemprop=name><meta itemprop=description></span><header class=post-header><h2 itemprop="name headline" class=post-title><a class=post-title-link href=/2021/02/28/%E9%97%B2%E8%81%8A%E4%B8%8B%E4%B9%98%E5%85%AC%E4%BA%A4%E7%9A%84%E7%94%A8%E6%88%B7%E4%BD%93%E9%AA%8C/ itemprop=url>闲聊下乘公交的用户体验</a></h2><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间：2021-02-28 21:56:42" datetime=2021-02-28T21:56:42+08:00>2021-02-28</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/%E7%94%9F%E6%B4%BB/ itemprop=url rel=index><span itemprop=name>生活</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/%E7%94%9F%E6%B4%BB/%E5%85%AC%E4%BA%A4/ itemprop=url rel=index><span itemprop=name>公交</span></a> </span></span><span class="post-meta-item leancloud_visitors" data-flag-title=闲聊下乘公交的用户体验 id=/2021/02/28/%E9%97%B2%E8%81%8A%E4%B8%8B%E4%B9%98%E5%85%AC%E4%BA%A4%E7%9A%84%E7%94%A8%E6%88%B7%E4%BD%93%E9%AA%8C/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数：</span> <span class=leancloud-visitors-count></span> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-comment"></i> </span><span class=post-meta-item-text>Disqus：</span> <a href=/2021/02/28/%E9%97%B2%E8%81%8A%E4%B8%8B%E4%B9%98%E5%85%AC%E4%BA%A4%E7%9A%84%E7%94%A8%E6%88%B7%E4%BD%93%E9%AA%8C/#disqus_thread itemprop=discussionUrl title=disqus><span class="post-comments-count disqus-comment-count" data-disqus-identifier=2021/02/28/闲聊下乘公交的用户体验/ itemprop=commentCount></span></a></span></div></div></header><div class=post-body itemprop=articleBody><p>新年开工开车来杭州，因为没有车位加限行今天来就没开车来了，从东站做公交回住的地方，这班神奇的车我之前也吐槽过了，有神奇的乘客和神奇的司机，因为基本上这班车是从我毕业就开始乘了，所以也算是比较熟悉了，以前总体感觉不太好的是乘坐时间太长了，不过这个也不能怪车，是我自己住得远（离东站），后来住到了现在的地方，也算是直达，并且 LD 比较喜欢直达的，不爱更快却要换乘的地铁，所以坐的频率比较高，也说过前面那些比较气人的乘客，自己不好好戴口罩，反而联合一起上车的乘客诽谤司机，说他要吃人了要打人了，也正是这个司机比较有意思，上车就让戴好口罩，还给大家讲，哪里哪里又有疫情了，我觉得其实这个司机还是不错的，特殊时期，对于这种公共交通，这样的确是比较负责任的做法，只是说话方式，语气这个因人而异，他也不是来伺候人的，而且这么一大车人，说了一遍不行，再说一遍，三遍以上了，嗓门大一点也属于正常的人的行为。<br>还是说回今天要说的，今天这位司机我看着跟前面说的那位有点像，因为上车的时候比较暗没看清脸，主要原因是这位司机开车比较猛，比较急，然后车上因为这个时间点，比较多大学开学来的学生，拎着个行李箱，一开始是前面已经都站满了人，后面还有很多空位，因为后面没地方放行李箱，就因为这样前面站着的有几个就在说司机开慢点，结果司机貌似也没听进去，还是我行我素，过了会又有人说司机开稳一点，就在这个人说完没一会，停在红绿灯路口的车里，就有人问有没有垃圾桶，接着又让司机开门，说晕车太严重了，要下车，司机开了门，我望出去两个妹子下了车，好像在路边草丛吐了，前面开门下车的时候就有人说她们第一次来杭州，可能有点责怪司机开的不稳，也影响了杭州交通给新来杭州的人的感受，说完了事情经过，其实我有蛮多感触，对于杭州公交司机，我大概是大一来了没多久，陪室友去文三路买电脑就晕车，下车的时候在公交车站吐了，可能是从大学开始缺乏锻炼，又饮食不规律，更加容易晕车，大部分晕车我觉得都是我自己的原因，有时候是上车前吃太多了，或者早上起太早，没睡好，没吃东西，反正自己也是挺多原因的，说到司机的原因的话，我觉得可能这班车还算好的，最让我难受的还是上下班高峰的时候，因为经过的那条路是比较重要的主干道，路比较老比较窄，并且还有很多人行道，所以经常一脚油门连带着一脚刹车，真的很难受，这种算是我觉得真的是公交体验比较差的一点，但是这一点呢也不能完全怪公交司机，杭州的路政规划是很垃圾，没看错，是垃圾，所以总体结论是公交还行，主要是路政规划就是垃圾，包括这条主干道这么多人行道，并且两边都是老小区，老年人在上班高峰可能要买菜送娃或者其他事情，在通畅的情况下可能只需要六分钟的路程，有时候因为各种原因，半小时都开不完，扯开去一点，杭州的路，核心的高速说封就封，本来是高架可以直接通到城西，结果没造，到了路本已经很拥挤的时候开始来造隧道，各种破坏，隧道接高架的地方，无尽的加塞，对于我这样的小白司机来说真的是太恶心了，所以我一直想说的就是杭州这个地方房价领先基础设施十年，地铁，高架，高速通通不行，地面道路就更不行了。<br>总结下，其实杭州的真正的公交体验差，应该还是路造成的，对于前面的那两位妹子来说，有可能是她们来自于公交司机都是开的特别稳，并且路况也很好的地方，也或者是我被虐习惯了🤦♂️</div><footer class=post-footer><div class=post-eof></div></footer></article></div><div class=post-block><article class=post-content itemscope itemtype=http://schema.org/Article><link href=https://nicksxs.me/2021/02/21/AQS-%E4%B9%8B-Condition-%E6%B5%85%E6%9E%90%E7%AC%94%E8%AE%B0/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="learn from zero,技术博客，Nicksxs，史学森" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="undefined | Nicksxs's Blog" itemprop=name><meta itemprop=description></span><header class=post-header><h2 itemprop="name headline" class=post-title><a class=post-title-link href=/2021/02/21/AQS-%E4%B9%8B-Condition-%E6%B5%85%E6%9E%90%E7%AC%94%E8%AE%B0/ itemprop=url>AQS篇二 之 Condition 浅析笔记</a></h2><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间：2021-02-21 21:27:06" datetime=2021-02-21T21:27:06+08:00>2021-02-21</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar-check"></i> </span><span class=post-meta-item-text>更新于</span> <time title="修改时间：2022-06-11 22:45:11" datetime=2022-06-11T22:45:11+08:00 itemprop=dateModified>2022-06-11</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/ itemprop=url rel=index><span itemprop=name>Java</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/%E5%B9%B6%E5%8F%91/ itemprop=url rel=index><span itemprop=name>并发</span></a> </span></span><span class="post-meta-item leancloud_visitors" data-flag-title="AQS篇二 之 Condition 浅析笔记" id=/2021/02/21/AQS-%E4%B9%8B-Condition-%E6%B5%85%E6%9E%90%E7%AC%94%E8%AE%B0/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数：</span> <span class=leancloud-visitors-count></span> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-comment"></i> </span><span class=post-meta-item-text>Disqus：</span> <a href=/2021/02/21/AQS-%E4%B9%8B-Condition-%E6%B5%85%E6%9E%90%E7%AC%94%E8%AE%B0/#disqus_thread itemprop=discussionUrl title=disqus><span class="post-comments-count disqus-comment-count" data-disqus-identifier=2021/02/21/AQS-之-Condition-浅析笔记/ itemprop=commentCount></span></a></span></div></div></header><div class=post-body itemprop=articleBody><p>Condition也是 AQS 中很重要的一块内容，可以先看段示例代码，这段代码应该来自于Doug Lea大大，可以在 javadoc 中的 <a href=https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/Condition.html rel=noopener target=_blank>condition</a> 部分找到，其实大大原来写过基于 <code>synchronized</code> 实现的，后面我也贴下代码<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>locks<span class="token punctuation">.</span></span><span class="token class-name">Condition</span></span><span class="token punctuation">;</span>
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<span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>locks<span class="token punctuation">.</span></span><span class="token class-name">Lock</span></span><span class="token punctuation">;</span>
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<span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>locks<span class="token punctuation">.</span></span><span class="token class-name">ReentrantLock</span></span><span class="token punctuation">;</span>
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<span class="token keyword">class</span> <span class="token class-name">BoundedBuffer</span> <span class="token punctuation">{</span>
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<span class="token keyword">final</span> <span class="token class-name">Lock</span> lock <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ReentrantLock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token comment">// condition 依赖于 lock 来产生</span>
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<span class="token keyword">final</span> <span class="token class-name">Condition</span> notFull <span class="token operator">=</span> lock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">final</span> <span class="token class-name">Condition</span> notEmpty <span class="token operator">=</span> lock<span class="token punctuation">.</span><span class="token function">newCondition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token comment">// 对象池子，put 跟 take 的就是这里的</span>
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<span class="token keyword">final</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> items <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token number">100</span><span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token keyword">int</span> putptr<span class="token punctuation">,</span> takeptr<span class="token punctuation">,</span> count<span class="token punctuation">;</span>
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<span class="token comment">// 生产</span>
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<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">put</span><span class="token punctuation">(</span><span class="token class-name">Object</span> x<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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<span class="token comment">// 这里也说明了，需要先拥有锁</span>
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lock<span class="token punctuation">.</span><span class="token function">lock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">try</span> <span class="token punctuation">{</span>
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<span class="token keyword">while</span> <span class="token punctuation">(</span>count <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span>
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notFull<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 队列已满，等待，直到 not full 才能继续生产</span>
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items<span class="token punctuation">[</span>putptr<span class="token punctuation">]</span> <span class="token operator">=</span> x<span class="token punctuation">;</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>putptr <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span> putptr <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
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<span class="token operator">++</span>count<span class="token punctuation">;</span>
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notEmpty<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 生产成功，队列已经 not empty 了，发个通知出去</span>
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<span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
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lock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span>
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<span class="token comment">// 消费</span>
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<span class="token keyword">public</span> <span class="token class-name">Object</span> <span class="token function">take</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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lock<span class="token punctuation">.</span><span class="token function">lock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">try</span> <span class="token punctuation">{</span>
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<span class="token keyword">while</span> <span class="token punctuation">(</span>count <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span>
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notEmpty<span class="token punctuation">.</span><span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 队列为空，等待，直到队列 not empty，才能继续消费</span>
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<span class="token class-name">Object</span> x <span class="token operator">=</span> items<span class="token punctuation">[</span>takeptr<span class="token punctuation">]</span><span class="token punctuation">;</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>takeptr <span class="token operator">==</span> items<span class="token punctuation">.</span>length<span class="token punctuation">)</span> takeptr <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
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<span class="token operator">--</span>count<span class="token punctuation">;</span>
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notFull<span class="token punctuation">.</span><span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 被我消费掉一个，队列 not full 了，发个通知出去</span>
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<span class="token keyword">return</span> x<span class="token punctuation">;</span>
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<span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
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lock<span class="token punctuation">.</span><span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>介绍下 Condition 的结构<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">ConditionObject</span> <span class="token keyword">implements</span> <span class="token class-name">Condition</span><span class="token punctuation">,</span> <span class="token class-name"><span class="token namespace">java<span class="token punctuation">.</span>io<span class="token punctuation">.</span></span>Serializable</span> <span class="token punctuation">{</span>
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<span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> <span class="token keyword">long</span> serialVersionUID <span class="token operator">=</span> <span class="token number">1173984872572414699L</span><span class="token punctuation">;</span>
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<span class="token comment">/** First node of condition queue. */</span>
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<span class="token keyword">private</span> <span class="token keyword">transient</span> <span class="token class-name">Node</span> firstWaiter<span class="token punctuation">;</span>
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<span class="token comment">/** Last node of condition queue. */</span>
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<span class="token keyword">private</span> <span class="token keyword">transient</span> <span class="token class-name">Node</span> lastWaiter<span class="token punctuation">;</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>主要的就这么点，而且也复用了 AQS 阻塞队列或者大大叫 <code>lock queue</code>中同样的 Node 节点，只不过它没有使用其中的双向队列，也就是prev 和 next，而是在 Node 中的 nextWaiter，所以只是个单向的队列，没使用 next 其实还有个用处，后面会提到，看下结构的示意图<br><img data-src=https://img.nicksxs.com/uPic/Ss9oFX.png><br>然后主要是看两个方法，<code>await</code> 和 <code>signal</code>,<br>先来看下 await<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
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* Implements interruptible condition wait.
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* <ol>
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* <li> If current thread is interrupted, throw InterruptedException.
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* <li> Save lock state returned by {@link #getState}.
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* <li> Invoke {@link #release} with saved state as argument,
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* throwing IllegalMonitorStateException if it fails.
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* <li> Block until signalled or interrupted.
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* <li> Reacquire by invoking specialized version of
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* {@link #acquire} with saved state as argument.
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* <li> If interrupted while blocked in step 4, throw InterruptedException.
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* </ol>
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*/</span>
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<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">void</span> <span class="token function">await</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">interrupted</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
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<span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token comment">// 将当前节点包装成一个 condition waiter node 节点</span>
|
|
<span class="token class-name">Node</span> node <span class="token operator">=</span> <span class="token function">addConditionWaiter</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token comment">// 完全释放占有的锁，这里需要是占有锁的线程</span>
|
|
<span class="token keyword">int</span> savedState <span class="token operator">=</span> <span class="token function">fullyRelease</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">int</span> interruptMode <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token comment">// 判断下是否在阻塞队列中，因为有可能被其他节点从等待队列移动到阻塞队列</span>
|
|
<span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">isOnSyncQueue</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// park等待，等待被唤醒</span>
|
|
<span class="token class-name">LockSupport</span><span class="token punctuation">.</span><span class="token function">park</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>interruptMode <span class="token operator">=</span> <span class="token function">checkInterruptWhileWaiting</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">break</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
|
|
<span class="token comment">// 被唤醒后进入阻塞队列，等待获取锁，这里继续用了fullyRelease返回的 state</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">acquireQueued</span><span class="token punctuation">(</span>node<span class="token punctuation">,</span> savedState<span class="token punctuation">)</span> <span class="token operator">&&</span> interruptMode <span class="token operator">!=</span> <span class="token constant">THROW_IE</span><span class="token punctuation">)</span>
|
|
interruptMode <span class="token operator">=</span> <span class="token constant">REINTERRUPT</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>node<span class="token punctuation">.</span>nextWaiter <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token comment">// clean up if cancelled</span>
|
|
<span class="token function">unlinkCancelledWaiters</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>interruptMode <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token function">reportInterruptAfterWait</span><span class="token punctuation">(</span>interruptMode<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>添加条件队列节点<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Adds a new waiter to wait queue.
|
|
* @return its new wait node
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token class-name">Node</span> <span class="token function">addConditionWaiter</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> t <span class="token operator">=</span> lastWaiter<span class="token punctuation">;</span>
|
|
<span class="token comment">// If lastWaiter is cancelled, clean out.</span>
|
|
<span class="token comment">// 如果节点已经不是 CONDITION 状态了，表示已经取消了</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t <span class="token operator">!=</span> <span class="token keyword">null</span> <span class="token operator">&&</span> t<span class="token punctuation">.</span>waitStatus <span class="token operator">!=</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CONDITION</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 把等待队列中取消的节点清理出去</span>
|
|
<span class="token function">unlinkCancelledWaiters</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
t <span class="token operator">=</span> lastWaiter<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">// 把当前线程包装成waitStatus=CONDITION 的节点</span>
|
|
<span class="token class-name">Node</span> node <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Node</span><span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">currentThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CONDITION</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 没有 lastWaiter 节点，直接是 firstWaiter</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
firstWaiter <span class="token operator">=</span> node<span class="token punctuation">;</span>
|
|
<span class="token keyword">else</span>
|
|
<span class="token comment">// 不然就接在 lastWaiter 后面</span>
|
|
t<span class="token punctuation">.</span>nextWaiter <span class="token operator">=</span> node<span class="token punctuation">;</span>
|
|
<span class="token comment">// 当前节点就会变成新的 lastWaiter</span>
|
|
lastWaiter <span class="token operator">=</span> node<span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> node<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>清理取消的节点<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Unlinks cancelled waiter nodes from condition queue.
|
|
* Called only while holding lock. This is called when
|
|
* cancellation occurred during condition wait, and upon
|
|
* insertion of a new waiter when lastWaiter is seen to have
|
|
* been cancelled. This method is needed to avoid garbage
|
|
* retention in the absence of signals. So even though it may
|
|
* require a full traversal, it comes into play only when
|
|
* timeouts or cancellations occur in the absence of
|
|
* signals. It traverses all nodes rather than stopping at a
|
|
* particular target to unlink all pointers to garbage nodes
|
|
* without requiring many re-traversals during cancellation
|
|
* storms.
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">unlinkCancelledWaiters</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> t <span class="token operator">=</span> firstWaiter<span class="token punctuation">;</span>
|
|
<span class="token class-name">Node</span> trail <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 循环遍历单向链表的节点，如果状态不是 CONDITION 就清出去</span>
|
|
<span class="token keyword">while</span> <span class="token punctuation">(</span>t <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> next <span class="token operator">=</span> t<span class="token punctuation">.</span>nextWaiter<span class="token punctuation">;</span>
|
|
<span class="token comment">// 循环链表操作，清掉取消的节点</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t<span class="token punctuation">.</span>waitStatus <span class="token operator">!=</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CONDITION</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
t<span class="token punctuation">.</span>nextWaiter <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>trail <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
firstWaiter <span class="token operator">=</span> next<span class="token punctuation">;</span>
|
|
<span class="token keyword">else</span>
|
|
trail<span class="token punctuation">.</span>nextWaiter <span class="token operator">=</span> next<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>next <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
lastWaiter <span class="token operator">=</span> trail<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">else</span>
|
|
trail <span class="token operator">=</span> t<span class="token punctuation">;</span>
|
|
t <span class="token operator">=</span> next<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>完全释放锁<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Invokes release with current state value; returns saved state.
|
|
* Cancels node and throws exception on failure.
|
|
* @param node the condition node for this wait
|
|
* @return previous sync state
|
|
*/</span>
|
|
<span class="token keyword">final</span> <span class="token keyword">int</span> <span class="token function">fullyRelease</span><span class="token punctuation">(</span><span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">boolean</span> failed <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">try</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 获取下当前的 state 值，因为是可重入的，所以这个值要保存下来</span>
|
|
<span class="token keyword">int</span> savedState <span class="token operator">=</span> <span class="token function">getState</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 这里还包含比较多操作，不过跟前面分析 AQS 的释放比较类似，不深入了</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">release</span><span class="token punctuation">(</span>savedState<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
failed <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 返回这个值</span>
|
|
<span class="token keyword">return</span> savedState<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalMonitorStateException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>failed<span class="token punctuation">)</span>
|
|
node<span class="token punctuation">.</span>waitStatus <span class="token operator">=</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CANCELLED</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>判断是否在阻塞队列中<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Returns true if a node, always one that was initially placed on
|
|
* a condition queue, is now waiting to reacquire on sync queue.
|
|
* @param node the node
|
|
* @return true if is reacquiring
|
|
*/</span>
|
|
<span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">isOnSyncQueue</span><span class="token punctuation">(</span><span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 如果waitStatus 是 CONDITION 或者没有 prev 前置节点肯定就不在</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>node<span class="token punctuation">.</span>waitStatus <span class="token operator">==</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CONDITION</span> <span class="token operator">||</span> node<span class="token punctuation">.</span>prev <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 这里就是我前面提到的 next 的作用</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>node<span class="token punctuation">.</span>next <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token comment">// If has successor, it must be on queue</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 从 tail 开始找，是否在阻塞队列中</span>
|
|
<span class="token comment">/*
|
|
* node.prev can be non-null, but not yet on queue because
|
|
* the CAS to place it on queue can fail. So we have to
|
|
* traverse from tail to make sure it actually made it. It
|
|
* will always be near the tail in calls to this method, and
|
|
* unless the CAS failed (which is unlikely), it will be
|
|
* there, so we hardly ever traverse much.
|
|
*/</span>
|
|
<span class="token keyword">return</span> <span class="token function">findNodeFromTail</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">/**
|
|
* Returns true if node is on sync queue by searching backwards from tail.
|
|
* Called only when needed by isOnSyncQueue.
|
|
* @return true if present
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token keyword">boolean</span> <span class="token function">findNodeFromTail</span><span class="token punctuation">(</span><span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> t <span class="token operator">=</span> tail<span class="token punctuation">;</span>
|
|
<span class="token comment">// 从 tail 开始，从后往前找</span>
|
|
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token punctuation">;</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t <span class="token operator">==</span> node<span class="token punctuation">)</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
t <span class="token operator">=</span> t<span class="token punctuation">.</span>prev<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>await 的逻辑差不多就是这样子，主要的就是把自己包成一个 Node 节点，waitStatus 的状态是 CONDITION，挂在等待队列的最后，然后完全释放锁，park 等待<h2 id=signal><a class=headerlink href=#signal title=signal></a>signal</h2><pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Moves the longest-waiting thread, if one exists, from the
|
|
* wait queue for this condition to the wait queue for the
|
|
* owning lock.
|
|
*
|
|
* @throws IllegalMonitorStateException if {@link #isHeldExclusively}
|
|
* returns {@code false}
|
|
*/</span>
|
|
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">void</span> <span class="token function">signal</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">isHeldExclusively</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalMonitorStateException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// firstWaiter 肯定是最早开始等待的</span>
|
|
<span class="token class-name">Node</span> first <span class="token operator">=</span> firstWaiter<span class="token punctuation">;</span>
|
|
<span class="token comment">// 如果不为空就唤醒</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>first <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
<span class="token function">doSignal</span><span class="token punctuation">(</span>first<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">/**
|
|
* Removes and transfers nodes until hit non-cancelled one or
|
|
* null. Split out from signal in part to encourage compilers
|
|
* to inline the case of no waiters.
|
|
* @param first (non-null) the first node on condition queue
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">doSignal</span><span class="token punctuation">(</span><span class="token class-name">Node</span> first<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">do</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 因为要去唤醒 first 节点了，firstWaiter 需要再从后面找一个</span>
|
|
<span class="token comment">// 并且判断是否为空，如果是空的话就直接可以把 lastWaiter 设置成空了</span>
|
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<span class="token keyword">if</span> <span class="token punctuation">(</span> <span class="token punctuation">(</span>firstWaiter <span class="token operator">=</span> first<span class="token punctuation">.</span>nextWaiter<span class="token punctuation">)</span> <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
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lastWaiter <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
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<span class="token comment">// first 不需要继续保存后面的 waiter 了，因为 firstWaiter 已经是 first 的后置节点了</span>
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first<span class="token punctuation">.</span>nextWaiter <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
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<span class="token comment">// 如果 first 节点转移不成功，并且 firstWaiter 节点不为空，则继续进入循环</span>
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<span class="token punctuation">}</span> <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">transferForSignal</span><span class="token punctuation">(</span>first<span class="token punctuation">)</span> <span class="token operator">&&</span>
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<span class="token punctuation">(</span>first <span class="token operator">=</span> firstWaiter<span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token comment">/**
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* Transfers a node from a condition queue onto sync queue.
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* Returns true if successful.
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|
* @param node the node
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* @return true if successfully transferred (else the node was
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|
* cancelled before signal)
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*/</span>
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<span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">transferForSignal</span><span class="token punctuation">(</span><span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token comment">/*
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* If cannot change waitStatus, the node has been cancelled.
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*/</span>
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<span class="token comment">// 如果状态已经不是 CONDITION 就不会设置成功，返回 false</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">compareAndSetWaitStatus</span><span class="token punctuation">(</span>node<span class="token punctuation">,</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">CONDITION</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
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<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
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<span class="token comment">/*
|
|
* Splice onto queue and try to set waitStatus of predecessor to
|
|
* indicate that thread is (probably) waiting. If cancelled or
|
|
* attempt to set waitStatus fails, wake up to resync (in which
|
|
* case the waitStatus can be transiently and harmlessly wrong).
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|
*/</span>
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<span class="token comment">// 调用跟aqs 第一篇中一样的 enq 方法进入阻塞队列，返回入队后的前一节点</span>
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<span class="token class-name">Node</span> p <span class="token operator">=</span> <span class="token function">enq</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">int</span> ws <span class="token operator">=</span> p<span class="token punctuation">.</span>waitStatus<span class="token punctuation">;</span>
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<span class="token comment">// 将前置节点状态设置成SIGNAL，表示后面有节点在等了</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span>ws <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">||</span> <span class="token operator">!</span><span class="token function">compareAndSetWaitStatus</span><span class="token punctuation">(</span>p<span class="token punctuation">,</span> ws<span class="token punctuation">,</span> <span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">SIGNAL</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
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|
<span class="token class-name">LockSupport</span><span class="token punctuation">.</span><span class="token function">unpark</span><span class="token punctuation">(</span>node<span class="token punctuation">.</span>thread<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token comment">// 返回 true，上一个方法的循环就退出了</span>
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|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
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|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>这里其实就是把 condition 等待队列的第一个未取消的节点入队到阻塞队列去争锁<h2 id=附录><a class=headerlink href=#附录 title=附录></a>附录</h2><p><code>synchronized</code> 版的 BoundedBuffer<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/*
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|
File: BoundedBuffer.java
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|
|
|
Originally written by Doug Lea and released into the public domain.
|
|
This may be used for any purposes whatsoever without acknowledgment.
|
|
Thanks for the assistance and support of Sun Microsystems Labs,
|
|
and everyone contributing, testing, and using this code.
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|
|
|
History:
|
|
Date Who What
|
|
11Jun1998 dl Create public version
|
|
17Jul1998 dl Simplified by eliminating wait counts
|
|
25aug1998 dl added peek
|
|
5May1999 dl replace % with conditional (slightly faster)
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|
*/</span>
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<span class="token keyword">package</span> <span class="token constant">EDU</span><span class="token punctuation">.</span>oswego<span class="token punctuation">.</span>cs<span class="token punctuation">.</span>dl<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">;</span>
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<span class="token comment">/**
|
|
* Efficient array-based bounded buffer class.
|
|
* Adapted from CPJ, chapter 8, which describes design.
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|
* <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>] <p>
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|
**/</span>
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<span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">BoundedBuffer</span> <span class="token keyword">implements</span> <span class="token class-name">BoundedChannel</span> <span class="token punctuation">{</span>
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<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token class-name">Object</span><span class="token punctuation">[</span><span class="token punctuation">]</span> array_<span class="token punctuation">;</span> <span class="token comment">// the elements</span>
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<span class="token keyword">protected</span> <span class="token keyword">int</span> takePtr_ <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token comment">// circular indices</span>
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|
<span class="token keyword">protected</span> <span class="token keyword">int</span> putPtr_ <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
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<span class="token keyword">protected</span> <span class="token keyword">int</span> usedSlots_ <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token comment">// length</span>
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<span class="token keyword">protected</span> <span class="token keyword">int</span> emptySlots_<span class="token punctuation">;</span> <span class="token comment">// capacity - length</span>
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<span class="token comment">/**
|
|
* Helper monitor to handle puts.
|
|
**/</span>
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|
<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token class-name">Object</span> putMonitor_ <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Object</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
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|
<span class="token comment">/**
|
|
* Create a BoundedBuffer with the given capacity.
|
|
* @exception IllegalArgumentException if capacity less or equal to zero
|
|
**/</span>
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|
<span class="token keyword">public</span> <span class="token class-name">BoundedBuffer</span><span class="token punctuation">(</span><span class="token keyword">int</span> capacity<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">IllegalArgumentException</span> <span class="token punctuation">{</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span>capacity <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalArgumentException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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array_ <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Object</span><span class="token punctuation">[</span>capacity<span class="token punctuation">]</span><span class="token punctuation">;</span>
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|
emptySlots_ <span class="token operator">=</span> capacity<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
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|
|
|
<span class="token comment">/**
|
|
* Create a buffer with the current default capacity
|
|
**/</span>
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|
|
|
<span class="token keyword">public</span> <span class="token class-name">BoundedBuffer</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">this</span><span class="token punctuation">(</span><span class="token class-name">DefaultChannelCapacity</span><span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
<span class="token punctuation">}</span>
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|
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|
<span class="token comment">/**
|
|
* Return the number of elements in the buffer.
|
|
* This is only a snapshot value, that may change
|
|
* immediately after returning.
|
|
**/</span>
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|
<span class="token keyword">public</span> <span class="token keyword">synchronized</span> <span class="token keyword">int</span> <span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> usedSlots_<span class="token punctuation">;</span> <span class="token punctuation">}</span>
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<span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">capacity</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> array_<span class="token punctuation">.</span>length<span class="token punctuation">;</span> <span class="token punctuation">}</span>
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<span class="token keyword">protected</span> <span class="token keyword">void</span> <span class="token function">incEmptySlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">synchronized</span><span class="token punctuation">(</span>putMonitor_<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token operator">++</span>emptySlots_<span class="token punctuation">;</span>
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|
putMonitor_<span class="token punctuation">.</span><span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
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<span class="token keyword">protected</span> <span class="token keyword">synchronized</span> <span class="token keyword">void</span> <span class="token function">incUsedSlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token operator">++</span>usedSlots_<span class="token punctuation">;</span>
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<span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
<span class="token punctuation">}</span>
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<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token keyword">void</span> <span class="token function">insert</span><span class="token punctuation">(</span><span class="token class-name">Object</span> x<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// mechanics of put</span>
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|
<span class="token operator">--</span>emptySlots_<span class="token punctuation">;</span>
|
|
array_<span class="token punctuation">[</span>putPtr_<span class="token punctuation">]</span> <span class="token operator">=</span> x<span class="token punctuation">;</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>putPtr_ <span class="token operator">>=</span> array_<span class="token punctuation">.</span>length<span class="token punctuation">)</span> putPtr_ <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
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|
<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token class-name">Object</span> <span class="token function">extract</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// mechanics of take</span>
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|
<span class="token operator">--</span>usedSlots_<span class="token punctuation">;</span>
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|
<span class="token class-name">Object</span> old <span class="token operator">=</span> array_<span class="token punctuation">[</span>takePtr_<span class="token punctuation">]</span><span class="token punctuation">;</span>
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|
array_<span class="token punctuation">[</span>takePtr_<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
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|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">++</span>takePtr_ <span class="token operator">>=</span> array_<span class="token punctuation">.</span>length<span class="token punctuation">)</span> takePtr_ <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> old<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
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<span class="token keyword">public</span> <span class="token class-name">Object</span> <span class="token function">peek</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">synchronized</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">if</span> <span class="token punctuation">(</span>usedSlots_ <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">return</span> array_<span class="token punctuation">[</span>takePtr_<span class="token punctuation">]</span><span class="token punctuation">;</span>
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|
<span class="token keyword">else</span>
|
|
<span class="token keyword">return</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
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|
|
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<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">put</span><span class="token punctuation">(</span><span class="token class-name">Object</span> x<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">if</span> <span class="token punctuation">(</span>x <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalArgumentException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">interrupted</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
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|
<span class="token keyword">synchronized</span><span class="token punctuation">(</span>putMonitor_<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">while</span> <span class="token punctuation">(</span>emptySlots_ <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">try</span> <span class="token punctuation">{</span> putMonitor_<span class="token punctuation">.</span><span class="token function">wait</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
|
|
<span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">InterruptedException</span> ex<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
putMonitor_<span class="token punctuation">.</span><span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">throw</span> ex<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token function">insert</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token function">incUsedSlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
|
|
<span class="token keyword">public</span> <span class="token keyword">boolean</span> <span class="token function">offer</span><span class="token punctuation">(</span><span class="token class-name">Object</span> x<span class="token punctuation">,</span> <span class="token keyword">long</span> msecs<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>x <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalArgumentException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">interrupted</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token keyword">synchronized</span><span class="token punctuation">(</span>putMonitor_<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">long</span> start <span class="token operator">=</span> <span class="token punctuation">(</span>msecs <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token operator">?</span> <span class="token number">0</span> <span class="token operator">:</span> <span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">long</span> waitTime <span class="token operator">=</span> msecs<span class="token punctuation">;</span>
|
|
<span class="token keyword">while</span> <span class="token punctuation">(</span>emptySlots_ <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>waitTime <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">try</span> <span class="token punctuation">{</span> putMonitor_<span class="token punctuation">.</span><span class="token function">wait</span><span class="token punctuation">(</span>waitTime<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
|
|
<span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">InterruptedException</span> ex<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
putMonitor_<span class="token punctuation">.</span><span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">throw</span> ex<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
waitTime <span class="token operator">=</span> msecs <span class="token operator">-</span> <span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> start<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token function">insert</span><span class="token punctuation">(</span>x<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token function">incUsedSlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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|
|
|
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<span class="token keyword">public</span> <span class="token class-name">Object</span> <span class="token function">take</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">interrupted</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token class-name">Object</span> old <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
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<span class="token keyword">synchronized</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">while</span> <span class="token punctuation">(</span>usedSlots_ <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">try</span> <span class="token punctuation">{</span> <span class="token function">wait</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
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<span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">InterruptedException</span> ex<span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token keyword">throw</span> ex<span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span>
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old <span class="token operator">=</span> <span class="token function">extract</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token function">incEmptySlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
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<span class="token keyword">return</span> old<span class="token punctuation">;</span>
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|
<span class="token punctuation">}</span>
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|
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<span class="token keyword">public</span> <span class="token class-name">Object</span> <span class="token function">poll</span><span class="token punctuation">(</span><span class="token keyword">long</span> msecs<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">interrupted</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
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|
<span class="token class-name">Object</span> old <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">synchronized</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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|
<span class="token keyword">long</span> start <span class="token operator">=</span> <span class="token punctuation">(</span>msecs <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token operator">?</span> <span class="token number">0</span> <span class="token operator">:</span> <span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">long</span> waitTime <span class="token operator">=</span> msecs<span class="token punctuation">;</span>
|
|
|
|
<span class="token keyword">while</span> <span class="token punctuation">(</span>usedSlots_ <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>waitTime <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token keyword">return</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">try</span> <span class="token punctuation">{</span> <span class="token function">wait</span><span class="token punctuation">(</span>waitTime<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
|
|
<span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">InterruptedException</span> ex<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token function">notify</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">throw</span> ex<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
waitTime <span class="token operator">=</span> msecs <span class="token operator">-</span> <span class="token punctuation">(</span><span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> start<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token punctuation">}</span>
|
|
old <span class="token operator">=</span> <span class="token function">extract</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token function">incEmptySlots</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> old<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
|
|
<span class="token punctuation">}</span>
|
|
<span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div><footer class=post-footer><div class=post-eof></div></footer></article></div><div class=post-block><article class=post-content itemscope itemtype=http://schema.org/Article><link href=https://nicksxs.me/2021/02/14/AQS%E7%AF%87%E4%B8%80/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="learn from zero,技术博客，Nicksxs，史学森" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="undefined | Nicksxs's Blog" itemprop=name><meta itemprop=description></span><header class=post-header><h2 itemprop="name headline" class=post-title><a class=post-title-link href=/2021/02/14/AQS%E7%AF%87%E4%B8%80/ itemprop=url>AQS篇一</a></h2><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间：2021-02-14 22:51:54" datetime=2021-02-14T22:51:54+08:00>2021-02-14</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar-check"></i> </span><span class=post-meta-item-text>更新于</span> <time title="修改时间：2021-02-28 20:02:18" datetime=2021-02-28T20:02:18+08:00 itemprop=dateModified>2021-02-28</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/ itemprop=url rel=index><span itemprop=name>Java</span></a> </span>， <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/%E5%B9%B6%E5%8F%91/ itemprop=url rel=index><span itemprop=name>并发</span></a> </span></span><span class="post-meta-item leancloud_visitors" data-flag-title=AQS篇一 id=/2021/02/14/AQS%E7%AF%87%E4%B8%80/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数：</span> <span class=leancloud-visitors-count></span> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-comment"></i> </span><span class=post-meta-item-text>Disqus：</span> <a href=/2021/02/14/AQS%E7%AF%87%E4%B8%80/#disqus_thread itemprop=discussionUrl title=disqus><span class="post-comments-count disqus-comment-count" data-disqus-identifier=2021/02/14/AQS篇一/ itemprop=commentCount></span></a></span></div></div></header><div class=post-body itemprop=articleBody><p>很多东西都是时看时新，而且时间长了也会忘，所以再来复习下，也会有一些新的角度看法这次来聊下AQS的内容，主要是这几个点，<h2 id=第一个线程><a class=headerlink href=#第一个线程 title=第一个线程></a>第一个线程</h2><p>第一个线程抢到锁了，此时state跟阻塞队列是怎么样的，其实这里是之前没理解对的地方<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Fair version of tryAcquire. Don't grant access unless
|
|
* recursive call or no waiters or is first.
|
|
*/</span>
|
|
<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">tryAcquire</span><span class="token punctuation">(</span><span class="token keyword">int</span> acquires<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">final</span> <span class="token class-name">Thread</span> current <span class="token operator">=</span> <span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">currentThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">int</span> c <span class="token operator">=</span> <span class="token function">getState</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 这里如果state还是0说明锁还空着</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 因为是公平锁版本的，先去看下是否阻塞队列里有排着队的</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">hasQueuedPredecessors</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">&&</span>
|
|
<span class="token function">compareAndSetState</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> acquires<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 没有排队的，并且state使用cas设置成功的就标记当前占有锁的线程是我</span>
|
|
<span class="token function">setExclusiveOwnerThread</span><span class="token punctuation">(</span>current<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 然后其实就返回了，包括阻塞队列的head和tail节点和waitStatus都没有设置</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>current <span class="token operator">==</span> <span class="token function">getExclusiveOwnerThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">int</span> nextc <span class="token operator">=</span> c <span class="token operator">+</span> acquires<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>nextc <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">Error</span><span class="token punctuation">(</span><span class="token string">"Maximum lock count exceeded"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token function">setState</span><span class="token punctuation">(</span>nextc<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">// 这里就是第二个线程会返回false</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><h2 id=第二个线程><a class=headerlink href=#第二个线程 title=第二个线程></a>第二个线程</h2><p>当第二个线程进来的时候应该是怎么样，结合代码来看<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Acquires in exclusive mode, ignoring interrupts. Implemented
|
|
* by invoking at least once {@link #tryAcquire},
|
|
* returning on success. Otherwise the thread is queued, possibly
|
|
* repeatedly blocking and unblocking, invoking {@link
|
|
* #tryAcquire} until success. This method can be used
|
|
* to implement method {@link Lock#lock}.
|
|
*
|
|
* @param arg the acquire argument. This value is conveyed to
|
|
* {@link #tryAcquire} but is otherwise uninterpreted and
|
|
* can represent anything you like.
|
|
*/</span>
|
|
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">void</span> <span class="token function">acquire</span><span class="token punctuation">(</span><span class="token keyword">int</span> arg<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 前面第一种情况是tryAcquire直接成功了，这个if判断第一个条件就是false，就不往下执行了</span>
|
|
<span class="token comment">// 如果是第二个线程，第一个条件获取锁不成功，条件判断!tryAcquire(arg) == true，就会走</span>
|
|
<span class="token comment">// acquireQueued(addWaiter(Node.EXCLUSIVE), arg)</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">tryAcquire</span><span class="token punctuation">(</span>arg<span class="token punctuation">)</span> <span class="token operator">&&</span>
|
|
<span class="token function">acquireQueued</span><span class="token punctuation">(</span><span class="token function">addWaiter</span><span class="token punctuation">(</span><span class="token class-name">Node</span><span class="token punctuation">.</span><span class="token constant">EXCLUSIVE</span><span class="token punctuation">)</span><span class="token punctuation">,</span> arg<span class="token punctuation">)</span><span class="token punctuation">)</span>
|
|
<span class="token function">selfInterrupt</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>然后来看下addWaiter的逻辑<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Creates and enqueues node for current thread and given mode.
|
|
*
|
|
* @param mode Node.EXCLUSIVE for exclusive, Node.SHARED for shared
|
|
* @return the new node
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token class-name">Node</span> <span class="token function">addWaiter</span><span class="token punctuation">(</span><span class="token class-name">Node</span> mode<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 这里是包装成一个node</span>
|
|
<span class="token class-name">Node</span> node <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">Node</span><span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">currentThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> mode<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// Try the fast path of enq; backup to full enq on failure</span>
|
|
<span class="token comment">// 最快的方式就是把当前线程的节点放在阻塞队列的最后</span>
|
|
<span class="token class-name">Node</span> pred <span class="token operator">=</span> tail<span class="token punctuation">;</span>
|
|
<span class="token comment">// 只有当tail，也就是pred不为空的时候可以直接接上</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>pred <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
node<span class="token punctuation">.</span>prev <span class="token operator">=</span> pred<span class="token punctuation">;</span>
|
|
<span class="token comment">// 如果这里cas成功了，就直接接上返回了</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">compareAndSetTail</span><span class="token punctuation">(</span>pred<span class="token punctuation">,</span> node<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
pred<span class="token punctuation">.</span>next <span class="token operator">=</span> node<span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> node<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">// 不然就会继续走到这里</span>
|
|
<span class="token function">enq</span><span class="token punctuation">(</span>node<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> node<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>然后就是enq的逻辑了<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Inserts node into queue, initializing if necessary. See picture above.
|
|
* @param node the node to insert
|
|
* @return node's predecessor
|
|
*/</span>
|
|
<span class="token keyword">private</span> <span class="token class-name">Node</span> <span class="token function">enq</span><span class="token punctuation">(</span><span class="token keyword">final</span> <span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token punctuation">;</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 如果状态没变化的话，tail这时还是null的</span>
|
|
<span class="token class-name">Node</span> t <span class="token operator">=</span> tail<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t <span class="token operator">==</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// Must initialize</span>
|
|
<span class="token comment">// 这里就会初始化头结点，就是个空节点</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">compareAndSetHead</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">Node</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
|
|
<span class="token comment">// tail也赋值成head</span>
|
|
tail <span class="token operator">=</span> head<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 这里就设置tail了</span>
|
|
node<span class="token punctuation">.</span>prev <span class="token operator">=</span> t<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">compareAndSetTail</span><span class="token punctuation">(</span>t<span class="token punctuation">,</span> node<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
t<span class="token punctuation">.</span>next <span class="token operator">=</span> node<span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> t<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre><p>所以从这里可以看出来，其实head头结点不是个真实的带有线程的节点，并且不是在第一个线程进来的时候设置的<h2 id=解锁><a class=headerlink href=#解锁 title=解锁></a>解锁</h2><p>通过代码来看下<pre class="line-numbers language-java" data-language=java><code class=language-java><span class="token comment">/**
|
|
* Attempts to release this lock.
|
|
*
|
|
* <p>If the current thread is the holder of this lock then the hold
|
|
* count is decremented. If the hold count is now zero then the lock
|
|
* is released. If the current thread is not the holder of this
|
|
* lock then {@link IllegalMonitorStateException} is thrown.
|
|
*
|
|
* @throws IllegalMonitorStateException if the current thread does not
|
|
* hold this lock
|
|
*/</span>
|
|
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">unlock</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 释放锁</span>
|
|
sync<span class="token punctuation">.</span><span class="token function">release</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">/**
|
|
* Releases in exclusive mode. Implemented by unblocking one or
|
|
* more threads if {@link #tryRelease} returns true.
|
|
* This method can be used to implement method {@link Lock#unlock}.
|
|
*
|
|
* @param arg the release argument. This value is conveyed to
|
|
* {@link #tryRelease} but is otherwise uninterpreted and
|
|
* can represent anything you like.
|
|
* @return the value returned from {@link #tryRelease}
|
|
*/</span>
|
|
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">release</span><span class="token punctuation">(</span><span class="token keyword">int</span> arg<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 尝试去释放</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">tryRelease</span><span class="token punctuation">(</span>arg<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> h <span class="token operator">=</span> head<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>h <span class="token operator">!=</span> <span class="token keyword">null</span> <span class="token operator">&&</span> h<span class="token punctuation">.</span>waitStatus <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token function">unparkSuccessor</span><span class="token punctuation">(</span>h<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">protected</span> <span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">tryRelease</span><span class="token punctuation">(</span><span class="token keyword">int</span> releases<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token keyword">int</span> c <span class="token operator">=</span> <span class="token function">getState</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> releases<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token class-name">Thread</span><span class="token punctuation">.</span><span class="token function">currentThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token function">getExclusiveOwnerThread</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
|
|
<span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalMonitorStateException</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">boolean</span> free <span class="token operator">=</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 判断是否完全释放锁，因为可重入</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>c <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
free <span class="token operator">=</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token function">setExclusiveOwnerThread</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token function">setState</span><span class="token punctuation">(</span>c<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> free<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token comment">// 这段代码和上面的一致，只是为了顺序性，又拷下来看下</span>
|
|
|
|
<span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">boolean</span> <span class="token function">release</span><span class="token punctuation">(</span><span class="token keyword">int</span> arg<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">// 尝试去释放，如果是完全释放，返回的就是true，否则是false</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">tryRelease</span><span class="token punctuation">(</span>arg<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token class-name">Node</span> h <span class="token operator">=</span> head<span class="token punctuation">;</span>
|
|
<span class="token comment">// 这里判断头结点是否为空以及waitStatus的状态，前面说了head节点其实是</span>
|
|
<span class="token comment">// 在第二个线程进来的时候初始化的，如果是空的话说明没后续节点，并且waitStatus</span>
|
|
<span class="token comment">// 也表示了后续的等待状态</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>h <span class="token operator">!=</span> <span class="token keyword">null</span> <span class="token operator">&&</span> h<span class="token punctuation">.</span>waitStatus <span class="token operator">!=</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token function">unparkSuccessor</span><span class="token punctuation">(</span>h<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">return</span> <span class="token boolean">false</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
|
|
<span class="token comment">/**
|
|
* Wakes up node's successor, if one exists.
|
|
*
|
|
* @param node the node
|
|
*/</span>
|
|
<span class="token comment">// 唤醒后继节点</span>
|
|
<span class="token keyword">private</span> <span class="token keyword">void</span> <span class="token function">unparkSuccessor</span><span class="token punctuation">(</span><span class="token class-name">Node</span> node<span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
<span class="token comment">/*
|
|
* If status is negative (i.e., possibly needing signal) try
|
|
* to clear in anticipation of signalling. It is OK if this
|
|
* fails or if status is changed by waiting thread.
|
|
*/</span>
|
|
<span class="token keyword">int</span> ws <span class="token operator">=</span> node<span class="token punctuation">.</span>waitStatus<span class="token punctuation">;</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>ws <span class="token operator"><</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
<span class="token function">compareAndSetWaitStatus</span><span class="token punctuation">(</span>node<span class="token punctuation">,</span> ws<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
|
|
<span class="token comment">/*
|
|
* Thread to unpark is held in successor, which is normally
|
|
* just the next node. But if cancelled or apparently null,
|
|
* traverse backwards from tail to find the actual
|
|
* non-cancelled successor.
|
|
*/</span>
|
|
<span class="token class-name">Node</span> s <span class="token operator">=</span> node<span class="token punctuation">.</span>next<span class="token punctuation">;</span>
|
|
<span class="token comment">// 如果后继节点是空或者当前节点取消等待了</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>s <span class="token operator">==</span> <span class="token keyword">null</span> <span class="token operator">||</span> s<span class="token punctuation">.</span>waitStatus <span class="token operator">></span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
|
|
s <span class="token operator">=</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
|
|
<span class="token comment">// 从后往前找，找到非取消的节点，注意这里不是找到就退出，而是一直找到头</span>
|
|
<span class="token comment">// 所以不必担心中间有取消的</span>
|
|
<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token class-name">Node</span> t <span class="token operator">=</span> tail<span class="token punctuation">;</span> t <span class="token operator">!=</span> <span class="token keyword">null</span> <span class="token operator">&&</span> t <span class="token operator">!=</span> node<span class="token punctuation">;</span> t <span class="token operator">=</span> t<span class="token punctuation">.</span>prev<span class="token punctuation">)</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>t<span class="token punctuation">.</span>waitStatus <span class="token operator"><=</span> <span class="token number">0</span><span class="token punctuation">)</span>
|
|
s <span class="token operator">=</span> t<span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span>
|
|
<span class="token keyword">if</span> <span class="token punctuation">(</span>s <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span>
|
|
<span class="token comment">// 将其唤醒</span>
|
|
<span class="token class-name">LockSupport</span><span class="token punctuation">.</span><span class="token function">unpark</span><span class="token punctuation">(</span>s<span class="token punctuation">.</span>thread<span class="token punctuation">)</span><span class="token punctuation">;</span>
|
|
<span class="token punctuation">}</span><span aria-hidden=true class=line-numbers-rows><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre></div><footer class=post-footer><div class=post-eof></div></footer></article></div><nav class=pagination><a class="extend prev" aria-label=上一页 href=/page/28/ rel=prev title=上一页><i class="fa fa-angle-left"></i></a><a class=page-number href=/>1</a><span class=space>…</span><a class=page-number href=/page/28/>28</a><span class="page-number current">29</span><a class=page-number href=/page/30/>30</a><span class=space>…</span><a class=page-number href=/page/47/>47</a><a class="extend next" aria-label=下一页 href=/page/30/ rel=next title=下一页><i class="fa fa-angle-right"></i></a></nav></div></main><footer class=footer><div class=footer-inner><div class=beian><a href=https://beian.miit.gov.cn/ rel=noopener target=_blank>浙ICP备16002580号-2 </a><img alt src=/uploads/beian.png><a href=http://www.beian.gov.cn/portal/registerSystemInfo?recordcode=33010602011094 rel=noopener target=_blank>浙公网安备 33010602011094号</a></div><div class=copyright>© <span itemprop=copyrightYear>2023</span><span class=with-love><i class="fa 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