CPU中的乱序执行

https://blog.csdn.net/gjq_1988/article/details/39520729

测试demo

public class Test {
    static int x,y,a,b;

    public static void main(String[] args) throws InterruptedException {
        int i = 0;
        for (;;){
            i++;
            x = 0;
            y = 0;
            a = 0;
            b = 0;

            Thread one = new Thread(new Runnable() {
                public void run() {
                    a = 1;
                    x = b;
                }
            });

            Thread other = new Thread(new Runnable() {
                public void run() {
                    b = 1;
                    y = a;
                }
            });

            one.start();
            other.start();

            one.join();
            other.join();

            String result = "第" + i + ",x:" + x + ",y:" + y;

            //逻辑上是不会出现x=0且y=0的情况，除非存在乱序执行
            //就是a = 1;与x = b;换顺序，或者b = 1;与y = a;换顺序
            if (x ==0 && y ==0){
                System.out.println("出现乱序现象！！");
                break;
            }else{
                System.out.println(result);
            }
        }
    }

    /* 打印结果：
    第2696121,x:0,y:1
    第2696122,x:0,y:1
    第2696123,x:0,y:1
    第2696124,x:0,y:1
    第2696125,x:0,y:1
    第2696126,x:0,y:1
    出现乱序现象！！
     */
}