Java 线程池原理和队列详解

http://blog.csdn.net/xx326664162/article/details/51701508

参考：

http://blog.csdn.net/mazhimazh/article/details/19243889

http://shift-alt-ctrl.iteye.com/blog/1840385

http://dongxuan.iteye.com/blog/901689

http://blog.csdn.net/sd0902/article/details/8395677

http://shift-alt-ctrl.iteye.com/blog/1840385

线程池的框架图：

1、Executor任务提交接口与Executors工具类

Executor框架同Java.util.concurrent.Executor 接口在Java 5中被引入。Executor框架是一个根据一组执行策略调用，调度，执行和控制的异步任务的框架。Executor存在的目的是提供一种将“任务提交”与”任务如何运行”分离开来的机制。定义如下：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">interface</span> Executor {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> execute(Runnable command);
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

虽然只有一个方法，但是却为灵活且强大的异步任务执行框架提供了基础。它提供了一种标准的方法将任务的提交过程与执行过程解耦开来，并用Runnable来表示任务。

那么我们怎么得到Executor对象呢？这就是接下来要介绍的Exectors类了。

Executors为Executor，ExecutorService，ScheduledExecutorService，ThreadFactory和Callable类提供了一些工具方法，类似于集合中的Collections类的功能。Executors方便的创建线程池。

1、newCachedThreadPool

该线程池比较适合没有固定大小并且比较快速就能完成的小任务，它将为每个任务创建一个线程。那这样子它与直接创建线程对象（new Thread()）有什么区别呢？看到它的第三个参数60L和第四个参数TimeUnit.SECONDS了吗？好处就在于60秒内能够重用已创建的线程。

下面是Executors中的newCachedThreadPool()的源代码：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> ExecutorService <span class="hljs-title" style="box-sizing: border-box;">newCachedThreadPool</span>() {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, Integer.MAX_VALUE, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">60</span>L, TimeUnit.SECONDS, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SynchronousQueue<Runnable>());
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

2、 newFixedThreadPool

使用的Thread对象的数量是有限的,如果提交的任务数量大于限制的最大线程数，那么这些任务将排队，然后当有一个线程的任务结束之后，将会根据调度策略继续等待执行下一个任务。

下面是Executors中的newFixedThreadPool()的源代码：　

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> ExecutorService <span class="hljs-title" style="box-sizing: border-box;">newFixedThreadPool</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> nThreads) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(nThreads, nThreads, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>L, TimeUnit.MILLISECONDS,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinkedBlockingQueue<Runnable>());
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

3、newSingleThreadExecutor

线程数量为1的FixedThreadPool,如果提交了多个任务，那么这些任务将会排队，每个任务都会在下一个任务开始之前运行结束，所有的任务将会使用相同的线程。下面是Executors中的newSingleThreadExecutor()的源代码：　　

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> ExecutorService <span class="hljs-title" style="box-sizing: border-box;">newSingleThreadExecutor</span>() {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> FinalizableDelegatedExecutorService
(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>L, TimeUnit.MILLISECONDS, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinkedBlockingQueue<Runnable>()));
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

4、newScheduledThreadPool

创建一个固定长度的线程池，而且以延迟或定时的方式来执行任务。

通过如上配置的线程池的创建方法源代码，我们可以发现：

　　1> 除了CachedThreadPool使用的是直接提交策略的缓冲队列以外，其余两个用的采用的都是无界缓冲队列，也就说，FixedThreadPool和SingleThreadExecutor创建的线程数量就不会超过 corePoolSize。

　 2> 三个线程池采用的ThreadPoolExecutor构造方法都是同一个，使用的都是默认的ThreadFactory和handler:

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> RejectedExecutionHandler defaultHandler = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AbortPolicy();

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">ThreadPoolExecutor</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> corePoolSize,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> maximumPoolSize,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
Executors.defaultThreadFactory(), defaultHandler);
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

也就说三个线程池创建的线程对象都是同组，优先权等级为正常的Thread.NORM_PRIORITY（5）的非守护线程，使用的被拒绝任务处理方式是直接抛出异常的AbortPolicy策略（前面有介绍）。

二、ExecutorService任务周期管理接口

Executor的实现通常都会创建线程来执行任务，但是使用异步方式来执行任务时，由于之前提交任务的状态不是立即可见的，所以如果要关闭应用程序时，就需要将受影响的任务状态反馈给应用程序。

为了解决执行服务的生命周期问题，Executor扩展了EecutorService接口，添加了一些用于生命周期管理的方法。如下：

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">interface</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ExecutorService</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Executor</span> {</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> shutdown();
List<Runnable> shutdownNow();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> isShutdown();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> isTerminated();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> awaitTermination(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> timeout, TimeUnit unit) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> InterruptedException;
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 省略部分方法  </span>
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

三、ThreadPoolExecutor线程池实现类

先来看一下这个类中定义的重要变量，如下：

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> BlockingQueue<Runnable> workQueue;              <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 阻塞队列  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ReentrantLock mainLock = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ReentrantLock();   <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 互斥锁  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> HashSet<Worker> workers = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> HashSet<Worker>();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程集合.一个Worker对应一个线程  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> Condition termination = mainLock.newCondition();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 终止条件  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> largestPoolSize;           <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程池中线程数量曾经达到过的最大值。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> completedTaskCount;       <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 已完成任务数量  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> ThreadFactory threadFactory;     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// ThreadFactory对象，用于创建线程。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> RejectedExecutionHandler handler;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 拒绝策略的处理句柄  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> keepAliveTime;   <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程池维护线程所允许的空闲时间  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> allowCoreThreadTimeOut;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> corePoolSize;     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程池维护线程的最小数量，哪怕是空闲的  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">volatile</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> maximumPoolSize;  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程池维护的最大线程数量  </span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

其中有几个重要的规则需要说明一下：

1、 corePoolSize与maximumPoolSize

由于ThreadPoolExecutor 将根据 corePoolSize和 maximumPoolSize设置的边界自动调整池大小，当新任务在方法 execute(java.lang.Runnable) 中提交时：

如果运行的线程少于 corePoolSize，则创建新线程来处理请求，即使其他辅助线程是空闲的；

如果运行的线程等于或多于 corePoolSize 而少于 maximumPoolSize，

队列已满：创建新的线程去处理请求
队列未满：将任务加入队列

如果运行的线程多于corePoolSize 并且等于maximumPoolSize，

队列已满：通过handler所指定的策略来处理新请求；
队列未满：将任务加入队列

如果将 maximumPoolSize 设置为基本的无界值（如 Integer.MAX_VALUE），则并发任务的数量没有限制。

处理任务的优先级为：

核心线程corePoolSize > 任务队列workQueue > 最大线程maximumPoolSize，如果三者都满了，使用handler处理被拒绝的任务。
当池中的线程数大于corePoolSize的时候，多余的线程会等待keepAliveTime长的时间，如果无请求可处理就自行销毁。

2、workQueue 线程池所使用的缓冲队列

该缓冲队列的长度决定了能够缓冲的最大数量，缓冲队列有三种通用策略：

1、 直接提交。

　　

　　工作队列的默认选项是 SynchronousQueue，它将任务直接提交给线程而不保持它们。

　　在此，如果不存在可用于立即运行任务的线程，则试图把任务加入队列将失败，因此会构造一个新的线程。

　　此策略可以避免在处理可能具有内部依赖性的请求集时出现锁。直接提交通常要求无界 maximumPoolSizes 以避免拒绝新提交的任务。当命令以超过队列所能处理的平均数连续到达时，此策略允许无界线程具有增长的可能性;

　　

2、 无界队列

　　使用无界队列（例如，不具有预定义容量的 LinkedBlockingQueue）将导致在所有 corePoolSize 线程都忙时，新任务将在队列中等待。这样，创建的线程数量就不会超过 corePoolSize。（因此，maximumPoolSize 的值也就无效了。）

当每个任务完全独立于其他任务，即任务执行互不影响时，适合于使用无界队列；例如，在 Web 页服务器中。这种排队可用于处理瞬态突发请求，当命令以超过队列所能处理的平均数连续到达时，此策略允许无界线程具有增长的可能性;

　　

3、 有界队列

当使用有限的 maximumPoolSizes 时，有界队列（如 ArrayBlockingQueue）有助于防止资源耗尽，但是可能较难调整和控制。

队列大小和最大池大小可能需要相互折衷：使用大型队列和小型池可以最大限度地降低 CPU 使用率、操作系统资源和上下文切换开销，但是可能导致人工降低吞吐量。如果任务频繁阻塞（例如，如果它们是
I/O 边界），则系统可能为超过您许可的更多线程安排时间。使用小型队列通常要求较大的池大小，CPU 使用率较高，但是可能遇到不可接受的调度开销，这样也会降低吞吐量.

举例：

例子一：使用直接提交策略，也即SynchronousQueue。

首先SynchronousQueue是无界的，也就是说他存储任务的能力是没有限制的，但是由于该Queue本身的特性，在某次添加元素后必须等待其他线程取走后才能继续添加。在这里不是核心线程便是新创建的线程，但是我们试想一样下，下面的场景。

我们使用一下参数构造ThreadPoolExecutor：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">30</span>, TimeUnit.SECONDS,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span>  SynchronousQueue<Runnable>(),
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RecorderThreadFactory(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"CookieRecorderPool"</span>),
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.CallerRunsPolicy()); </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

假设当前核心线程已经有2个正在运行.

此时来了一个任务（A），根据前面介绍的“如果运行的线程等于或多于 corePoolSize，则 Executor 始终首选将请求加入队列，而不添加新的线程。”,所以A被添加到queue中。

又来了一个任务（B），且核心2个线程还没有忙完。接下来首先尝试1中描述，但是由于使用的SynchronousQueue，所以一定无法加入进去。

此时便满足了上面提到的“如果无法将请求加入队列，则创建新的线程，除非创建此线程超出maximumPoolSize，在这种情况下，任务将被拒绝。”，所以必然会新建一个线程来运行这个任务。

但是如果这三个任务都还没完成，继续来了一个任务，queue中无法插入（任务A还在queue中），而线程数达到了maximumPoolSize，所以只好执行异常策略了。

为了避免这种情况:，所以在使用SynchronousQueue通常要求maximumPoolSize是无界的（如果希望限制就直接使用有界队列）。对于使用SynchronousQueue的作用jdk中写的很清楚：此策略可以避免在处理可能具有内部依赖性的请求集时出现锁。

如果你的任务A1，A2有内部关联，A1需要先运行，那么先提交A1，再提交A2，当使用SynchronousQueue我们可以保证，A1必定先被执行，在A1么有被执行前，A2不可能添加入queue中

例子二：使用无界队列策略，即LinkedBlockingQueue

拿newFixedThreadPool来说，根据前文提到的规则：

如果运行的线程少于 corePoolSize，则 Executor 始终首选添加新的线程，而不进行排队。

那么当任务继续增加，会发生什么呢？

如果运行的线程等于或多于 corePoolSize，则 Executor 始终首选将请求加入队列，而不添加新的线程。

OK，此时任务变加入队列之中了，那什么时候才会添加新线程呢？

如果无法将请求加入队列，则创建新的线程，除非创建此线程超出 maximumPoolSize，在这种情况下，任务将被拒绝。

无界队列不会出现无法加入队列的情况。不像SynchronousQueue那样有其自身的特点，对于无界队列来说，总是可以加入的（资源耗尽，当然另当别论）。

换句说，永远也不会触发产生新的线程！线程数一直都是corePoolSize大小。忙完当前的线程，就从队列中拿任务开始运行。如果任务运行的时长比较长，而添加任务的速度远远超过处理任务的速度，任务队列就会疯长，任务内存很快就会爆掉

例子三：有界队列，使用ArrayBlockingQueue。

这个是最为复杂的使用，所以JDK不推荐使用也有些道理。与上面的相比，最大的特点便是可以防止资源耗尽的情况发生。

举例来说，请看如下构造方法：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">30</span>, TimeUnit.SECONDS,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayBlockingQueue<Runnable>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>),
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RecorderThreadFactory(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"CookieRecorderPool"</span>),
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.CallerRunsPolicy());  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

假设，所有的任务都永远无法执行完。

对于首先来的A,B来说直接运行
如果来了C,D，他们会被放到queu中
如果接下来再来E,F，则增加线程运行E，F。
但是如果再来任务，队列无法再接受了，线程数也到达最大的限制了，所以就会使用拒绝策略来处理。

3、ThreadFactory

使用 ThreadFactory 创建新线程。如果没有另外说明，则在同一个 ThreadGroup 中一律使用 Executors.defaultThreadFactory() 创建线程，并且这些线程具有相同的 NORM_PRIORITY 优先级和非守护进程状态。

通过提供不同的 ThreadFactory，可以改变线程的名称、线程组、优先级、守护进程状态等等。如果从 newThread 返回 null 时 ThreadFactory 未能创建线程，则执行程序将继续运行，但不能执行任何任务。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">interface</span> ThreadFactory {
Thread newThread(Runnable r);
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

而构造方法中的threadFactory对象，是通过 Executors.defaultThreadFactory()返回的。Executors.java中的defaultThreadFactory()源码如下：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> ThreadFactory <span class="hljs-title" style="box-sizing: border-box;">defaultThreadFactory</span>() {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> DefaultThreadFactory();
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

在DefaultThreadFactory类中实现了ThreadFactory接口并对其中定义的方法进行了实现，如下：

<code class="hljs axapta has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">DefaultThreadFactory</span> <span class="hljs-inheritance" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span></span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ThreadFactory</span> {</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> AtomicInteger poolNumber = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AtomicInteger(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ThreadGroup <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">group</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> AtomicInteger threadNumber = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AtomicInteger(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> String namePrefix;

DefaultThreadFactory() {
SecurityManager s = System.getSecurityManager();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">group</span> = (s != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) ? s.getThreadGroup() :  Thread.currentThread().getThreadGroup();
namePrefix = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"pool-"</span> +  poolNumber.getAndIncrement() +  <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"-thread-"</span>;
}
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 为线程池创建新的任务执行线程  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Thread newThread(Runnable r) {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 线程对应的任务是Runnable对象r  </span>
Thread t = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">group</span>, r,namePrefix + threadNumber.getAndIncrement(), <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设为非守护线程  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (t.isDaemon())
t.setDaemon(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>);
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 将优先级设为Thread.NORM_PRIORITY  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (t.getPriority() != Thread.NORM_PRIORITY)
t.setPriority(Thread.NORM_PRIORITY);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> t;
}
}  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li></ul>

4、RejectedExecutionHandler

当Executor已经关闭（即执行了executorService.shutdown()方法后），并且Executor将有限边界用于最大线程和工作队列容量，且已经饱和时，在方法execute()中提交的新任务将被拒绝.

　 在以上述情况下，execute 方法将调用其 RejectedExecutionHandler 的 RejectedExecutionHandler.rejectedExecution(java.lang.Runnable, java.util.concurrent.ThreadPoolExecutor) 方法。下面提供了四种预定义的处理程序策略：

在默认的 ThreadPoolExecutor.AbortPolicy 处理程序遭到拒绝将抛出运行时 RejectedExecutionException;

在 ThreadPoolExecutor.CallerRunsPolicy线程调用运行该任务的 execute 本身。此策略提供简单的反馈控制机制，能够减缓新任务的提交速度

在 ThreadPoolExecutor.DiscardPolicy 不能执行的任务将被删除;

在 ThreadPoolExecutor.DiscardOldestPolicy 如果执行程序尚未关闭，则位于工作队列头部的任务将被删除，然后重试执行程序（如果再次失败，则重复此过程）。

线程池默认会采用的是defaultHandler策略。首先看defaultHandler的定义：

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> RejectedExecutionHandler defaultHandler = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AbortPolicy(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 使用默认的拒绝策略  </span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">AbortPolicy</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">RejectedExecutionHandler</span> {</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">AbortPolicy</span>() { }
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 抛出异常  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">rejectedExecution</span>(Runnable r, ThreadPoolExecutor e) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> RejectedExecutionException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Task "</span> + r.toString() +  <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" rejected from "</span> +  e.toString());
}
} </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

看一下其他拒绝策略的具体实现。

<code class="hljs axapta has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyRunnable</span> <span class="hljs-inheritance" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span></span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Runnable</span> {</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> String name;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> MyRunnable(String name) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name = name;
}
@Override
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> run() {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
System.out.println(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.name + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">" is running."</span>);
Thread.sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>);
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (Exception e) {
e.printStackTrace();
}
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

举例：

如上是一个测试任务的例子，下面编写4个测试用例来测试。

1. DiscardPolicy 示例

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">DiscardPolicyDemo</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> THREADS_SIZE = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> CAPACITY = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> Exception {

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 创建线程池。线程池的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，"线程池"的阻塞队列容量为1(CAPACITY)。  </span>
ThreadPoolExecutor pool = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(THREADS_SIZE, THREADS_SIZE, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, TimeUnit.SECONDS, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayBlockingQueue<Runnable>(CAPACITY));
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置线程池的拒绝策略为"丢弃"  </span>
pool.setRejectedExecutionHandler(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.DiscardPolicy());

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 新建10个任务，并将它们添加到线程池中。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; i++) {
Runnable myrun = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"task-"</span>+i);
pool.execute(myrun);
}
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 关闭线程池  </span>
pool.shutdown();
}
}  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li></ul>

线程池pool的”最大池大小”和”核心池大小”都为1(THREADS_SIZE)，这意味着”线程池能同时运行的任务数量最大只能是1”。

线程池pool的阻塞队列是ArrayBlockingQueue，ArrayBlockingQueue是一个有界的阻塞队列，ArrayBlockingQueue的容量为1。这也意味着线程池的阻塞队列只能有一个线程池阻塞等待。

根据”“中分析的execute()代码可知：线程池中共运行了2个任务。第1个任务直接放到Worker中，通过线程去执行；第2个任务放到阻塞队列中等待。其他的任务都被丢弃了！

2. DiscardOldestPolicy 示例

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">DiscardOldestPolicyDemo</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> THREADS_SIZE = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> CAPACITY = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> Exception {

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 创建线程池。线程池的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，"线程池"的阻塞队列容量为1(CAPACITY)。  </span>
ThreadPoolExecutor pool = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(THREADS_SIZE, THREADS_SIZE, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, TimeUnit.SECONDS,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayBlockingQueue<Runnable>(CAPACITY));
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置线程池的拒绝策略为"DiscardOldestPolicy"  </span>
pool.setRejectedExecutionHandler(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.DiscardOldestPolicy());

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 新建10个任务，并将它们添加到线程池中。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; i++) {
Runnable myrun = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"task-"</span>+i);
pool.execute(myrun);
}
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 关闭线程池  </span>
pool.shutdown();
}
}  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

运行结果：

<code class="hljs applescript has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;">task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">9</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

将”线程池的拒绝策略”由DiscardPolicy修改为DiscardOldestPolicy之后，当有任务添加到线程池被拒绝时，线程池会丢弃阻塞队列中末尾的任务，然后将被拒绝的任务添加到末尾。

3. AbortPolicy 示例

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">AbortPolicyDemo</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> THREADS_SIZE = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> CAPACITY = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> Exception {

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 创建线程池。线程池的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，"线程池"的阻塞队列容量为1(CAPACITY)。  </span>
ThreadPoolExecutor pool = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(THREADS_SIZE, THREADS_SIZE, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, TimeUnit.SECONDS,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayBlockingQueue<Runnable>(CAPACITY));
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置线程池的拒绝策略为"抛出异常"  </span>
pool.setRejectedExecutionHandler(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.AbortPolicy());

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 新建10个任务，并将它们添加到线程池中。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; i++) {
Runnable myrun = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"task-"</span>+i);
pool.execute(myrun);
}
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (RejectedExecutionException e) {
e.printStackTrace();
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 关闭线程池  </span>
pool.shutdown();
}
}
}  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li></ul>

(某一次)运行结果：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;">java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.concurrent</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.RejectedExecutionException</span>
at java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.concurrent</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ThreadPoolExecutor</span>$AbortPolicy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.rejectedExecution</span>(ThreadPoolExecutor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.java</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1774</span>)
at java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.concurrent</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ThreadPoolExecutor</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.reject</span>(ThreadPoolExecutor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.java</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">768</span>)
at java<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.util</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.concurrent</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ThreadPoolExecutor</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.execute</span>(ThreadPoolExecutor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.java</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">656</span>)
at AbortPolicyDemo<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.main</span>(AbortPolicyDemo<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.java</span>:<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27</span>)
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> is running.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> is running.</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

将”线程池的拒绝策略”由DiscardPolicy修改为AbortPolicy之后，当有任务添加到线程池被拒绝时，会抛出RejectedExecutionException。

4. CallerRunsPolicy 示例

<code class="hljs java has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">CallerRunsPolicyDemo</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> THREADS_SIZE = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> CAPACITY = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">main</span>(String[] args) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> Exception {

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 创建线程池。线程池的"最大池大小"和"核心池大小"都为1(THREADS_SIZE)，"线程池"的阻塞队列容量为1(CAPACITY)。  </span>
ThreadPoolExecutor pool = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor(THREADS_SIZE, THREADS_SIZE, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, TimeUnit.SECONDS,
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ArrayBlockingQueue<Runnable>(CAPACITY));
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 设置线程池的拒绝策略为"CallerRunsPolicy"  </span>
pool.setRejectedExecutionHandler(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadPoolExecutor.CallerRunsPolicy());

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 新建10个任务，并将它们添加到线程池中。  </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; i < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; i++) {
Runnable myrun = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyRunnable(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"task-"</span>+i);
pool.execute(myrun);
}

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 关闭线程池  </span>
pool.shutdown();
}
}  </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul>

(某一次)运行结果：

<code class="hljs applescript has-numbering" style="display: block; padding: 0px; background: transparent; color: inherit; box-sizing: border-box; font-family: "Source Code Pro", monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal;">task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">8</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">9</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.
task-<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-property" style="box-sizing: border-box;">running</span>.</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right: 1px solid rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

将”线程池的拒绝策略”由DiscardPolicy修改为CallerRunsPolicy之后，当有任务添加到线程池被拒绝时，线程池会将被拒绝的任务添加到”线程池正在运行的线程”中取运行。