死锁AB-BA问题

 1 public class Main{
 2      public static void main(String[] args){
 3         System.out.println("演示开始");
 4            new Thread(()->{
 5              A.a();
 6            }).start();
 7            new Thread(()->{
 8              B.b();
 9            }).start();
10      }
11 
12      static class A{
13         public static synchronized void a(){
14             try{
15                 Thread.sleep(3000);    
16             }catch(Exception e){
17                 e.printStackTrace();
18             }
19             
20 
21             System.out.println("我拿到锁a了，锁b快到碗里来！");
22 
23             B.b();
24         }
25      }
26 
27      static class B{
28         public static synchronized void b(){
29             System.out.println("我拿到锁b了，锁a快到碗里来！");
30             try{
31                 Thread.sleep(3000);    
32             }catch(Exception e){
33                 e.printStackTrace();
34             }
35             A.a();
36         }
37      }
38  }