多线程编程<二>

wait()与notify():

 1 public class ThreadComDemo {
 2     public static void main(String[] args) {
 3         try {
 4             SyncOb sObj= new SyncOb();
 5
 6             new MyThread("MyThread", sObj);
 7
 8             for (int i = 0; i < 10; i++) {
 9                 Thread.sleep(250);
10                 System.out.print(".");
11             }
12             System.out.println();
13
14             sObj.goAhead();
15         } catch (InterruptedException e) {
16             System.out.println("Main thread interrupted.");
17         }
18     }
19 }
20
21
22 class MyThread implements Runnable {
23     SyncOb syncOb;
24
25     public MyThread( String name, SyncOb so) {
26         syncOb = so;
27         new Thread(this, name).start();
28     }
29
30     @Override
31     public void run() {
32         syncOb.waitFor();\\线程睡眠
33     }
34 }
35
36 class SyncOb {
37     boolean ready = false;
38     synchronized void waitFor() {
39         String thrdName = Thread.currentThread().getName();
40         System.out.println(thrdName + " is entering waitFor().");
41
42         System.out.println(thrdName + " calling wait() to wait for " + "notification to proceed.\n");
43
44         //调用wait()方法，这会使线程睡眠，并且会释放该对象的监视器。这样就允许另一个线程使用对象。
45         //在另一个线程进去同一个监视器并调用notify()之后，睡眠的线程会被唤醒。
46         try {
47             while(!ready) wait();//此处用的是while循环，而不是if.防止假唤醒。
48         } catch (InterruptedException e) {
49             System.out.println("Interrupted");
50         }
51         System.out.println(thrdName + " received notification and is" + " resuming execution.");
52     }
53
54     synchronized void goAhead() {
55         String thrdName = Thread.currentThread().getName();
56         System.out.println("\n" + thrdName + " thread calling notify() inside goAhead().\n" +
57         "This will let MyThread resume execution.\n");
58         ready = true;
59         notify();
60     }
61
62 }