java编程思想笔记-并发之后台线程

package com.tij.chapter1;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
/**
 * 
 * @author Allen
 * @date 2017-8-7
 *
 */
class DaemonThreadFactory implements ThreadFactory {
    @Override
    public Thread newThread(Runnable r) {
        Thread thread = new Thread(r);
        thread.setDaemon(true);
        return thread;
    }
}

class DaemonFromFactory implements Runnable {

    private String threadName;
    private CountDownLatch latch;

    public DaemonFromFactory(int i, CountDownLatch latch) {
        this.threadName = "thread-" + i;
        this.latch = latch;
    }

    @Override
    public void run() {
            while (true) {
                try {
                    TimeUnit.MILLISECONDS.sleep(100);
                    System.out.println(Thread.currentThread() + "--" + this);
                    System.out.println("count--" + latch.getCount());
                } catch (Exception e) {
                    e.printStackTrace();
                }finally{
                    latch.countDown();
                }

            }

    }

    @Override
    public String toString() {
        return threadName;
    }

}

public class DaemonTest {

    public static void main(String[] args) {
        CountDownLatch latch = new CountDownLatch(10);
        ExecutorService exec = Executors
                .newCachedThreadPool(new DaemonThreadFactory());
        for (int i = 0; i < 10; i++) {
            exec.execute(new DaemonFromFactory(i, latch));
        }
        System.out.println("All Threads Start");
        try {
            //latch.await(500, TimeUnit.MILLISECONDS);
            latch.await();
            //Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //主线程完成，则后台线程也全部中断
        System.out.println("Task Stopped");
    }
}

后台线程的finally语句不会执行，因为父线程即main线程执行结束后，jvm会关闭所有线程，可以通过Executor来实现有序的关闭线程