SingleThreadExecutor单线程线程池

package com.jiading.pool;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class singleThreadTest {
    public static void main(String[] args) {
        /**
         *  JAVA通过Executors提供了四种线程池，newSingleThreadExecutor创建的单线程线程池是其一
         * 单线程化的线程池
         * 那你如果要问单线程了为什么还要用线程池，只能是在一般情况下它是和单线程没区别的，但是如果这个唯一的线程因为异常结束，那么会有一个新的线程来替代它。
         * 这一点是单线程没办法做到的
         * 单线程线程池corePoolSize和maximumPoolSize都是1。所以绝对只有一个线程在执行，如果等待队列满了就直接拒绝执行新任务
         * 单线程线程池和定长线程池的阻塞队列使用的偶数LinkedBlockingQueue,默认的大小是int的最大值
         */
        ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();
        for(int i = 0;i < 10;i++) {
            final int index = i;//给变量加个final挺好，省的它变
            singleThreadExecutor.execute(new Runnable() {
                @Override
                public void run() {
                    Thread.currentThread().setName("Thread i = " + index);
                    System.out.println(Thread.currentThread().getName() + " index = " + index);
                    try {
                        Thread.sleep(500);
                        System.out.println("sleep finished");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            });
        }
        singleThreadExecutor.shutdown();
        System.out.println("on the main thread...");
    }

}

输出为:

on the main thread...
Thread i = 0 index = 0
sleep finished
Thread i = 1 index = 1
sleep finished
Thread i = 2 index = 2
sleep finished
Thread i = 3 index = 3
sleep finished
Thread i = 4 index = 4
sleep finished
Thread i = 5 index = 5
sleep finished
Thread i = 6 index = 6
sleep finished
Thread i = 7 index = 7
sleep finished
Thread i = 8 index = 8
sleep finished
Thread i = 9 index = 9
sleep finished

从输出也能看出来是只有一个线程了，sleep之后再唤醒。只要没有异常，一直是这一个