解读线程池-Executors的newSingleThreadExecutor和newFixedThreadPool(1)区别

import org.junit.Test;
 
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
 
public class ThreadPoolDemo {
    static class MyRunnable implements Runnable {
        @Override
        public void run() {
            System.out.println("开始");
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("结束" + Thread.currentThread().getName());
        }
    }
 
    @Test
    public void test() throws InterruptedException {
        //创建Runnable实例对象
        MyRunnable r = new MyRunnable();
 
        //创建线程池对象
        System.out.println("fixedThreadPool");
        ExecutorService fixedThreadPool = Executors.newFixedThreadPool(1);//包含1个线程对象
        for (int i = 0; i < 10; i++) {
            fixedThreadPool.submit(r);
        }
        Thread.sleep(10000);
        /**
         * 以上输出：
         * fixedThreadPool
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         * 开始
         * 结束pool-1-thread-1
         */
 
        System.out.println("singleThreadExecutor");
        ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();
        for (int i = 0; i < 10; i++) {
            singleThreadExecutor.submit(r);
        }
        Thread.sleep(10000);
        /**
         * 以上输出：
         * singleThreadExecutor
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         * 开始
         * 结束pool-2-thread-1
         */
 
        System.out.println("fixedThreadPool(5)");
        ((ThreadPoolExecutor) fixedThreadPool).setCorePoolSize(5);
        for (int i = 0; i < 10; i++) {
            fixedThreadPool.submit(r);
        }
        Thread.sleep(10000);
        /**
         * 以上输出：
         * fixedThreadPool(5)
         * 开始
         * 开始
         * 开始
         * 开始
         * 开始
         * 结束pool-1-thread-1
         * 结束pool-1-thread-5
         * 结束pool-1-thread-2
         * 结束pool-1-thread-3
         * 结束pool-1-thread-4
         * 开始
         * 结束pool-1-thread-4
         * 开始
         * 结束pool-1-thread-4
         * 开始
         * 结束pool-1-thread-4
         * 开始
         * 结束pool-1-thread-4
         * 开始
         * 结束pool-1-thread-4
         * singleThreadExecutor(5)
         */
 
        System.out.println("singleThreadExecutor(5)");
        ((ThreadPoolExecutor) singleThreadExecutor).setCorePoolSize(5);
        for (int i = 0; i < 10; i++) {
            singleThreadExecutor.submit(r);
        }
        /**
         * 以下输出：
         * Exception in thread "main" java.lang.ClassCastException: java.util.concurrent.Executors$FinalizableDelegatedExecutorService cannot be cast to java.util.concurrent.ThreadPoolExecutor
         * 	at ThreadPoolDemo.main(ThreadPoolDemo.java:33)
         */
    }
}