原址：http://auguslee.iteye.com/blog/1292203

Java Thread中， join() 方法主要是讓呼叫改方法的thread完成run方法裡面的東西后， 在執行join()方法後面的程式碼。示例：

class ThreadTesterA implements Runnable {  
2.  
3.    private int counter;  
4.  
5.    @Override  
6.    public void run() {  
7.        while (counter <= 10) {  
8.            System.out.print("Counter = " + counter + " ");  
9.            counter++;  
10.        }  
11.        System.out.println();  
12.    }  
13.}  
14.  
15.class ThreadTesterB implements Runnable {  
16.  
17.    private int i;  
18.  
19.    @Override  
20.    public void run() {  
21.        while (i <= 10) {  
22.            System.out.print("i = " + i + " ");  
23.            i++;  
24.        }  
25.        System.out.println();  
26.    }  
27.}  
28.  
29.public class ThreadTester {  
30.    public static void main(String[] args) throws InterruptedException {  
31.        Thread t1 = new Thread(new ThreadTesterA());  
32.        Thread t2 = new Thread(new ThreadTesterB());  
33.        t1.start();  
34.        t1.join(); // wait t1 to be finished  
35.        t2.start();  
36.        t2.join(); // in this program, this may be removed  
37.    }  
38.}  
 

如果去掉t1.join()這個語句過後， 輸出的書序是亂的， 加上這個語句過後， 就會按照順序輸出，  從某種意義上說實現了同步。