SummerVocation_Learning--java的线程死锁

Posted 2020-12-05 落花人独立微雨燕双飞

 1  
 2 public class Test_DeadLock implements Runnable {
 3  
 4     public int flag = 1;
 5     static Object o1 = new Object(),o2 = new Object();
 6     public void run() {
 7         System.out.println("flag= " + flag);
 8         if (flag == 1) {
 9             synchronized (o1) {  //o1锁定
10                 try {
11                     Thread.sleep(500);
12                 } catch (Exception e) {
13                     e.printStackTrace();
14                 }
15             synchronized (o2) { //只要再锁定o2，就能打印出1.
16                 System.out.println("1"); //但是o2被另一个线程锁定了，所以打印不出1.
17                 }
18             }
19         }
20         if (flag == 0) {
21             synchronized (o2) { //锁定o2
22                 try {
23                     Thread.sleep(500);
24                 } catch (Exception e) {
25                     e.printStackTrace();
26                 }
27             synchronized (o1) {  //只要再等待锁定o1，就能打印出0.
28                     System.out.println("0"); //但是o1另一个线程锁定，无法执行。两个线程被锁死，谁都无法完成执行。
29                 }
30             }
31         }
32     }
33     
34     public static void main(String[] args) {
35         Test_DeadLock t1 = new Test_DeadLock();
36         Test_DeadLock t2 = new Test_DeadLock();
37         t1.flag = 1;
38         t2.flag = 0;
39         Thread t11 = new Thread(t1);
40         Thread t21 = new Thread(t2);
41         t11.start(); t21.start();
42  
43     }
44     /*
45      * flag= 1
46        flag= 0
47                 两个线程产生死锁，synchronized的输出语句未被执行。
48      */
49  
50 }