Java Thread join() 的用法

Java Thread中， join() 方法是让调用该方法的主线程执行run()时暂时卡住，等run()执行完成后， 主线程再调用执行join()后面的代码。示例：

class ThreadTesterA implements Runnable {

	private int counter;

	@Override
	public void run() {
		while (counter <= 10) {
			System.out.print("Counter = " + counter + " ");
			counter++;
		}
		System.out.println();
	}
}

class ThreadTesterB implements Runnable {

	private int i;

	@Override
	public void run() {
		while (i <= 10) {
			System.out.print("i = " + i + " ");
			i++;
		}
		System.out.println();
	}
}

public class ThreadTester {
	public static void main(String[] args) throws InterruptedException {
		Thread t1 = new Thread(new ThreadTesterA());
		Thread t2 = new Thread(new ThreadTesterB());
		t1.start();
		t1.join(); // wait t1 to be finished
		t2.start();
		t2.join(); // in this program, this may be removed
	}
}

如果去掉t1.join()这个语句过后， 输出的顺序是乱的， 加上这个语句后， 就会按照顺序输出，  从某种意义上说实现了同步。

原文: https://my.oschina.net/u/2338362/blog/516237