Jdk版本：jdk1.8.0_151

代码

1public class SimpleHappenBefore {
2
3    public static void main(String[] args) throws InterruptedException {
4
5        for(int i=0;i<500000;i++){
6            SimpleHappenBefore.State state = new SimpleHappenBefore.State();
7            ThreadA threadA=new ThreadA(state);
8            ThreadB threadB=new ThreadB(state);
9            threadA.start();
10            threadB.start();
11
12            threadA.join();
13            threadB.join();
14        }
15    }
16
17    static class ThreadA extends Thread{
18
19        private final SimpleHappenBefore.State state;
20
21        ThreadA(SimpleHappenBefore.State state) {
22            this.state = state;
23        }
24
25        public void run(){
26            state.a=1;
27            state.b=1;
28            state.c=1;
29            state.d=1;
30        }
31    }
32
33    static class ThreadB extends Thread{
34
35        private final SimpleHappenBefore.State state;
36
37        ThreadB(SimpleHappenBefore.State state) {
38            this.state = state;
39        }
40
41        public void run(){
42            if(state.b==1 && state.a==0){
43                System.out.println("b=1");
44            }
45
46            if(state.c==1 && (state.b==0 || state.a == 0)){
47                System.out.println("c=1");
48            }
49
50            if(state.d==1 && (state.a==0 || state.b==0 || state.c==0)){
51                System.out.println("d==1");
52            }
53        }
54    }
55
56    static class State {
57        public int a = 0;
58        public int b = 0;
59        public int c = 0;
60        public int d = 0;
61    }
62}

输出

1d==1
2d==1
3c=1