主线程等待子线程完成的实现[join , wait-notify,CountDownLatch]方式

import java.util.concurrent.CountDownLatch;

public class TestThread
{
    static int cnt = 100;
    static int last = -1;
    static int type = 2;
    static int liveCnt = cnt;

    static CountDownLatch counter = new CountDownLatch(cnt);

    static class WorkThread extends Thread
    {
        Object lock = null;
        int id = -1;
        int sleep = -1;

        WorkThread(int id, Object lock)
        {
            this.id = id;
            this.lock = lock;
        }

        public void run()
        {
            try
            {
                work();
            } catch (Exception e)
            {
            }

            synchronized (lock)
            {
                //System.out.println("thread " + id + " done");

                last = sleep;
                liveCnt--;
                counter.countDown();
                lock.notify();
            }
        }

        private void work()
        {
            try
            {
                sleep = (int) (Math.random() * 1000 * 10);
                //System.out.println("thread " + id + " sleep=" + sleep);

                Thread.sleep(sleep);
            } catch (InterruptedException e)
            {
            }
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args)
    {
        String lock = "lock";

        long start = System.currentTimeMillis();

        WorkThread[] workers = new WorkThread[cnt];
        for (int i = 0; i < cnt; i++)
        {
            workers[i] = new WorkThread(i, lock);
            workers[i].start();
        }

        switch (type)
        {
            //join 方式

            case 1 :
                for (Thread worker : workers)
                {
                    try
                    {
                        worker.join();
                    } catch (InterruptedException e)
                    {
                    }
                }
                break;

            //wait - notify 方式    

            case 2 :
                while (true)
                {
                    synchronized (lock)
                    {
                        if (liveCnt == 0)
                            break;

                        try
                        {
                            lock.wait();
                        } catch (InterruptedException e)
                        {
                        }
                    }
                }

                //CountDownLatch 方式

            case 3 :
                try
                {
                    counter.await();
                } catch (InterruptedException e)
                {
                }
                break;
        }

        long end = System.currentTimeMillis();
        System.out.println("type=" + type);
        System.out.println("All done, elapse: " + (end - start));
        System.out.println("last=" + last);
        System.out.println("delay=" + (end - start - last));
    }
}