原文链接：

对newCachedThreadPool回收线程的证明

public class test{    public static void main(String[] args)    {        ExecutorService cachedThreadPool = Executors.newCachedThreadPool();        for (int i = 0; i < 10; i++) {            final int index = i;//            try {//                Thread.sleep(index * 1000);//            } catch (InterruptedException e) {//                e.printStackTrace();//            }                     cachedThreadPool.execute(new Runnable() {                         @Override                public void run() {                    System.out.println(index+" "+Thread.currentThread().getName()+" "+Thread.currentThread().hashCode());                }            });        }    }}

结果只是产生九个不同的线程

2 pool-1-thread-3 1176331429

5 pool-1-thread-6 573401305

3 pool-1-thread-4 227309514

1 pool-1-thread-2 407159979

6 pool-1-thread-7 860495101

7 pool-1-thread-8 185084417

0 pool-1-thread-1 1408899434

4 pool-1-thread-5 775593137

8 pool-1-thread-9 598837007

9 pool-1-thread-2 407159979

二次测试，只有5个

0 pool-1-thread-1 2087961100

2 pool-1-thread-3 1794419219

1 pool-1-thread-2 2016711653

4 pool-1-thread-1 2087961100

6 pool-1-thread-3 1794419219

5 pool-1-thread-2 2016711653

9 pool-1-thread-3 1794419219

8 pool-1-thread-2 2016711653

7 pool-1-thread-5 1444382773

3 pool-1-thread-4 847094661

三次测试，有6个

0 pool-1-thread-1 461277103

2 pool-1-thread-3 2016711653

4 pool-1-thread-5 847094661

3 pool-1-thread-4 1794419219

6 pool-1-thread-4 1794419219

7 pool-1-thread-5 847094661

8 pool-1-thread-1 461277103

5 pool-1-thread-3 2016711653

1 pool-1-thread-2 2087961100

9 pool-1-thread-6 1287333624

 

如果把中间休眠的注释去掉，效果更加明显，只有一个线程

0 pool-1-thread-1 2016711653

1 pool-1-thread-1 2016711653

2 pool-1-thread-1 2016711653

3 pool-1-thread-1 2016711653

4 pool-1-thread-1 2016711653

5 pool-1-thread-1 2016711653

6 pool-1-thread-1 2016711653

7 pool-1-thread-1 2016711653

8 pool-1-thread-1 2016711653

9 pool-1-thread-1 2016711653