线程池

import java.io.IOException;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;

public class TestThreadPoolExecutor {
    /*
    corePoolSize:指定了线程池中的线程数量，它的数量决定了添加的任务是开辟新的线程去执行，还是放到workQueue任务队列中去；
    当提交一个任务到线程池时，线程池会创建一个线程来执行任务，即使其他空闲的基本线程能够执行新任务也会创建线程，等到需要执行的任务数大于线程池基本大小时就不再创建。
    如果调用了线程池的prestartAllCoreThreads方法，线程池会提前创建并启动所有基本线程。
    maximumPoolSize:指定了线程池中的最大线程数量，这个参数会根据你使用的workQueue任务队列的类型，决定线程池会开辟的最大线程数量；
    如果队列满了，并且已创建的线程数小于最大线程数，则线程池会再创建新的线程执行任务。
    值得注意的是，如果使用了无界的任务队列这个参数就没用了

    执行：
    1、2任务直接压入1、2线程直接创建并执行，
    3任务放入缓冲队列，最大线程数未满，创建新线程执行3任务

     */
    public static void main(String[] args) throws InterruptedException, IOException {
        int corePoolSize = 2;
        int maximumPoolSize = 10;
        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);
        executor.prestartAllCoreThreads(); // 预启动所有核心线程

        for (int i = 1; i <= 10; i++) {
//            Thread.sleep(1);
            MyTask task = new MyTask(String.valueOf(i));
            executor.execute(task);
            System.out.println("当前队列数两"+executor.getQueue().size());
        }
        System.out.println(executor.getActiveCount());
        Thread.sleep(10000);
        System.out.println(executor.getActiveCount());
        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) {
//            try {
//                Thread.sleep(200);
//            } catch (InterruptedException e) {
//                e.printStackTrace();
//            }
            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 {

        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(1000); //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 + "]";
        }
    }
}