java自带的四种线程池实例详解

源码：
public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
        //ScheduledThreadPoolExecutor继承ThreadPoolExecutor
        return new ScheduledThreadPoolExecutor(corePoolSize);
    }
    
public ScheduledThreadPoolExecutor(int corePoolSize) {
    //ScheduledThreadPoolExecutor继承ThreadPoolExecutor，故super()会调用ThreadPoolExecutor的构造函数初始化并返回一个ThreadPoolExecutor，而ThreadPoolExecutor使实现ExecutorService接口的
    //最终ScheduledThreadPoolExecutor也和上面几种线程池一样返回的是ExecutorService接口的实现类ThreadPoolExecutor
    super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
          new DelayedWorkQueue());
}

public class ThreadTest {
    public static void main(String[] args) throws InterruptedException, IOException {
        int corePoolSize = 2;
        int maximumPoolSize = 4;
        long keepAliveTime = 10;
        TimeUnit unit = TimeUnit.SECONDS;
        BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(2);
        ThreadFactory threadFactory = new NameTreadFactory();
        RejectedExecutionHandler handler = new MyIgnorePolicy();
       ThreadPoolExecutor executor = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, unit,
                workQueue, threadFactory, handler);
        executor.prestartAllCoreThreads(); // 预启动所有核心线程        
        for (int i = 1; i <= 10; i++) {
            MyTask task = new MyTask(String.valueOf(i));
            executor.execute(task);
        }
        System.in.read(); //阻塞主线程
    }
    static class NameTreadFactory implements ThreadFactory {
        private final AtomicInteger mThreadNum = new AtomicInteger(1);
        @Override
        public Thread newThread(Runnable r) {
            Thread t = new Thread(r, "my-thread-" + mThreadNum.getAndIncrement());
            System.out.println(t.getName() + " has been created");
            return t;
        }
    }

    public static class MyIgnorePolicy implements RejectedExecutionHandler {
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            doLog(r, e);
        }
        private void doLog(Runnable r, ThreadPoolExecutor e) {
            // 可做日志记录等
            System.err.println( r.toString() + " rejected");
//          System.out.println("completedTaskCount: " + e.getCompletedTaskCount());
        }
    }

    static class MyTask implements Runnable {
        private String name;
        public MyTask(String name) {
            this.name = name;
        }
        @Override
        public void run() {
            try {
                System.out.println(this.toString() + " is running!");
                Thread.sleep(3000); //让任务执行慢点
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        public String getName() {
            return name;
        }
        @Override
        public String toString() {
            return "MyTask [name=" + name + "]";
        }
    }
}