sleep()与wait()的差别（java笔记-多线程）

Posted 2020-09-05

 1 package test;
 2 
 3 public class test1 {
 4 
 5     public static void main(String[] args) {
 6 
 7         new Thread(new thread1()).start();
 8         try {
 9             Thread.sleep(5000);
10         } catch (InterruptedException e) {
11 
12             e.printStackTrace();
13         }
14         new Thread(new thread2()).start();
15 
16     }
17 }
18 
19 class thread1 implements Runnable {
20 
21     @Override
22     public void run() {
23 
24         synchronized (test1.class) {
25             System.out.println("here is thread1");
26             System.out.println("thread1 is waiting");
27 
28             try {
29                 test1.class.wait();// 调用wait，会释放线程锁，进入等待锁定池，直到調用notify方法唤醒，再次进入对象锁定池准备获取对象锁进入运行状态。
30 
31             } catch (InterruptedException e) {
32 
33                 e.printStackTrace();
34             }
35             System.out.println("thread1 is going");
36             System.out.println("thread1 is over");
37         }
38     }
39 }
40 
41 class thread2 implements Runnable {
42 
43     @Override
44     public void run() {
45         //
46         synchronized (test1.class) {
47             System.out.println("here is thread2");
48             System.out.println("thread2 is sleeping");
49             test1.class.notify();
50             try {
51                 Thread.sleep(4000);// 调用sleep，会等待相应时间，等待时线程锁不释放，时间到了会进入运行状态；
52                 System.out.println("thread2 is going");
53                 System.out.println("thread2 is over");
54             } catch (InterruptedException e) {
55                 e.printStackTrace();
56             }
57         }
58     }
59 }

运行结果：

here is thread1
thread1 is waiting
here is thread2
thread2 is sleeping
thread2 is going
thread2 is over
thread1 is going
thread1 is over

注释掉49行的“test1.class.notify();”

程序会一直处于挂起状态：

 

here is thread1
thread1 is waiting
here is thread2
thread2 is sleeping
thread2 is going
thread2 is over

 

sleep()方法属于Thread类；wait()方法属于Object类。

在调用sleep()方法的过程中，线程不会释放对象锁。而当调用wait()方法的时候，线程会放弃对象锁，进入等待此对象的等待锁定池，只有针对此对象调用notify()方法后本线程才进入对象锁定池准备。

感谢大神 Hongten；