主线程等待所有子线程执行完成

使用CountDownLatch使主线程等待所有子线程执行完，再继续执行。

	public static void main(String[] args) throws InterruptedException {
		t1();
		t2();
	}

	private static long getTime() {
		return System.currentTimeMillis();
	}

	public static void t3() {
		long dd1 = System.currentTimeMillis();
		while (getTime() - dd1 <= 10000) {

		}
	}

	public static void t2() throws InterruptedException {
		long d1 = System.currentTimeMillis();
		int threadNumber = 10;
		final CountDownLatch countDownLatch = new CountDownLatch(threadNumber);
		for (int i = 0; i < threadNumber; i++) {
			final int threadID = i;
			new Thread() {
				public void run() {
					System.out.println("start" + threadID);
					t3();
					System.out.println("end" + threadID);
					System.out.println(String.format(
							"threadID:[%s] finished!!", threadID));
					countDownLatch.countDown();
				}
			}.start();
		}
		countDownLatch.await();
		System.out.println("main thread finished!!");
		long d2 = System.currentTimeMillis();
		System.out.println("time2:" + (d2 - d1));
	}

	public static void t1() throws InterruptedException {
		long d1 = System.currentTimeMillis();
		int threadNumber = 10;
		for (int i = 0; i < threadNumber; i++) {
			final int threadID = i;
			Thread thread = new Thread() {
				public void run() {
					System.out.println("start" + threadID);
					t3();
					System.out.println("end" + threadID);
					System.out.println(String.format(
							"threadID:[%s] finished!!", threadID));
				}
			};
			thread.start();
			thread.join();
		}
		System.out.println("main thread finished!!");
		long d2 = System.currentTimeMillis();
		System.out.println("time1:" + (d2 - d1));
	}

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