1 public class JoinTester01 implements Runnable {2 3     private String name;4 5     public JoinTester01(String name) {6     this.name = name;7     }8 9     public void run() {
10     System.out.printf("%s begins: %s\n", name, new Date());
11     try {
12         TimeUnit.SECONDS.sleep(4);
13     } catch (InterruptedException e) {
14         e.printStackTrace();
15     }
16     System.out.printf("%s has finished: %s\n", name, new Date());
17     }
18
19     public static void main(String[] args) {
20     Thread thread1 = new Thread(new JoinTester01("One"));
21     Thread thread2 = new Thread(new JoinTester01("Two"));
22     thread1.start();
23     thread2.start();
24
25     try {
26         thread1.join();
27         thread2.join();
28     } catch (InterruptedException e) {
29         // TODO Auto-generated catch block
30         e.printStackTrace();
31     }
32
33     System.out.println("Main thread is finished");
34     }
35
36 }

 1 /**2      *  Waits at most <code>millis</code> milliseconds for this thread to  3      * die. A timeout of <code>0</code> means to wait forever.    4      */5     //此处A timeout of 0 means to wait forever 字面意思是永远等待，其实是等到t结束后。6     public final synchronized void join(long millis)    throws InterruptedException {7         long base = System.currentTimeMillis();8         long now = 0;9
10         if (millis < 0) {
11             throw new IllegalArgumentException("timeout value is negative");
12         }
13
14         if (millis == 0) {
15             while (isAlive()) {
16                 wait(0);
17             }
18         } else {
19             while (isAlive()) {
20                 long delay = millis - now;
21                 if (delay <= 0) {
22                     break;
23                 }
24                 wait(delay);
25                 now = System.currentTimeMillis() - base;
26             }
27         }
28     }

 1 public class JoinTester02 implements Runnable {2 3     Thread thread;4 5     public JoinTester02(Thread thread) {6     this.thread = thread;7     }8 9     public void run() {
10     synchronized (thread) {
11         System.out.println("getObjectLock");
12         try {
13         Thread.sleep(9000);
14         } catch (InterruptedException ex) {
15         ex.printStackTrace();
16         }
17         System.out.println("ReleaseObjectLock");
18     }
19     }
20
21     public static void main(String[] args) {
22     Thread thread = new Thread(new JoinTester01("Three"));
23     Thread getLockThread = new Thread(new JoinTester02(thread));
24
25     getLockThread.start();
26     thread.start();
27
28     try {
29         thread.join();
30     } catch (InterruptedException e) {
31         // TODO Auto-generated catch block
32         e.printStackTrace();
33     }
34     System.out.println("Main finished!");
35     }
36
37 }public class JoinTester02 implements Runnable {
38
39     Thread thread;
40
41     public JoinTester02(Thread thread) {
42     this.thread = thread;
43     }
44
45     public void run() {
46     synchronized (thread) {
47         System.out.println("getObjectLock");
48         try {
49         Thread.sleep(9000);
50         } catch (InterruptedException ex) {
51         ex.printStackTrace();
52         }
53         System.out.println("ReleaseObjectLock");
54     }
55     }
56
57     public static void main(String[] args) {
58     Thread thread = new Thread(new JoinTester01("Three"));
59     Thread getLockThread = new Thread(new JoinTester02(thread));
60
61     getLockThread.start();
62     thread.start();
63
64     try {
65         thread.join();
66     } catch (InterruptedException e) {
67         // TODO Auto-generated catch block
68         e.printStackTrace();
69     }
70     System.out.println("Main finished!");
71     }
72
73 }