jvm-证明cpu指令是乱序执行的案例

package jvm;

/**
 * 证明cpu指令是乱序执行的
 *
 * @author 1
 * @version 1.0
 * @description: TODO
 * @date 2024-07-19 9:31
 */
public class T04_Disorder {
    private static int x = 0, y = 0;
    private static int a = 0, b =0;

    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() {
                @Override
                public void run() {
                    //由于线程one先启动，下面这句话让它等一等线程two. 读着可根据自己电脑的实际性能适当调整等待时间.
                    //shortWait(100000);
                    a = 1;
                    x = b;
                }
            });

            Thread other = new Thread(new Runnable() {
                @Override
                public void run() {
                    b = 1;
                    y = a;
                }
            });
            one.start();other.start();
            one.join();other.join();
            String result = "第" + i + "次 (" + x + "," + y + "）";
            //如果cpu是顺序指令执行的,那么上面两个线程,要么a=1则y=1或者b=1则x=1 也就是x和y不可能同时为0 除非 线程没有按照顺序执行
            if(x == 0 && y == 0) {
                System.err.println(result);
                break;
            } else {
                //System.out.println(result);
            }
        }
    }


    public static void shortWait(long interval){
        long start = System.nanoTime();
        long end;
        do{
            end = System.nanoTime();
        }while(start + interval >= end);
    }
}

执行结果: 第1661256次 (0,0）

证明了,cpu指令的确是乱序执行的;