对java线程池的一些理解和感悟

import java.util.Date;
import java.util.concurrent.*;

public class ThreadPoolTest {

    private static LinkedBlockingQueue queue = new LinkedBlockingQueue<Runnable>(4);
    
    private static ExecutorService pool = new ThreadPoolExecutor(4, 4,
            0L, TimeUnit.MILLISECONDS,queue
    );

    public static void main(String[] args) {
//        pool.execute(new aaa(0));
//        pool.execute(new aaa(1));
//        pool.execute(new aaa(2));
//        pool.execute(new aaa(3));
//
//        for(int i =4;i<13;i++){
//            final int num = i+1;
//
//            try {
//                System.out.println("queue.put第"+(i+1)+"个任务"+new Date());
//                queue.put(new aaa(num));
//                System.out.println("after queue.put 队列大小:"+queue.size());
//            } catch (InterruptedException e1) {
//                e1.printStackTrace();
//            }
//        }
        long start = +new Date().getTime();
        System.out.println("开始执行"+start);

        for(int i =0;i<100;i++){
            final int num = i+1;
            try {
                System.out.println("before-execute-阻塞队列大小:"+queue.size());
                System.out.println("before-execute-向线程池放置并execute第"+(i+1)+"个任务"+new Date());
                pool.execute(new Job(num));

            } catch (RejectedExecutionException e) {
               //阻塞队列慢，线程数达到最大线程数以后的默认抛弃策略
               //抛出RejectedExecutionException异常，开发者catch住自行处理，
               //这里catch住以后放入阻塞队列使得主线程阻塞，直到阻塞队列有位置
                System.out.println("-------------"+RejectedExecutionException.class.getName() + new Date());
                try {
                    queue.put(new Job(num));
                    System.out.println("before-put-阻塞队列大小:"+queue.size()+"  "+new Date());
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
            }
        }
        pool.shutdown();

        long end = +new Date().getTime();
        System.out.println("执行完毕，执行时间："+(start-end));
    }

    public static  class  Job implements Runnable {

        int num;
        public Job(int num) {
            this.num = num;
        }

        @Override
        public void run()  {
            System.out.println("任务"+num +"开始执行" + new Date());
            long startTime = new Date().getTime();

            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("任务"+num +"执行完毕"+new Date().getTime());

        }
    }

}

开始执行1513129646475
before-execute-阻塞队列大小:0
before-execute-向线程池放置并execute第1个任务Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:0
before-execute-向线程池放置并execute第2个任务Wed Dec 13 09:47:26 CST 2017
任务1开始执行Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:0
before-execute-向线程池放置并execute第3个任务Wed Dec 13 09:47:26 CST 2017
任务2开始执行Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:0
before-execute-向线程池放置并execute第4个任务Wed Dec 13 09:47:26 CST 2017
任务3开始执行Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:0
before-execute-向线程池放置并execute第5个任务Wed Dec 13 09:47:26 CST 2017
任务4开始执行Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:1
before-execute-向线程池放置并execute第6个任务Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:2
before-execute-向线程池放置并execute第7个任务Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:3
before-execute-向线程池放置并execute第8个任务Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:4
before-execute-向线程池放置并execute第9个任务Wed Dec 13 09:47:26 CST 2017
before-execute-阻塞队列大小:4
before-execute-向线程池放置并execute第10个任务Wed Dec 13 09:47:26 CST 2017
任务9开始执行Wed Dec 13 09:47:26 CST 2017
-------------java.util.concurrent.RejectedExecutionExceptionWed Dec 13 09:47:26 CST 2017
任务2执行完毕1513129649502
任务1执行完毕1513129649502