java下代码重排所可能产生的问题

import java.util.concurrent.CountDownLatch; /** * 代码重排示例 * 单例模式的DCL，当对象被分配空间后并且将内存的地址返回给对象后，其它线程再对实例做非空判断时已经不成立 */ public class Main { private static int x = 0, y = 0; private static int a = 0, b = 0; public static void main(String[] args) throws InterruptedException { for (long i = 0; i < Long.MAX_VALUE; i++) { x = 0; y = 0; a = 0; b = 0; CountDownLatch latch = new CountDownLatch(2); Thread thread = new Thread(() -> { a = 1; x = b; latch.countDown(); }); Thread thread1 = new Thread(() -> { b = 1; y = a; latch.countDown(); }); thread.start(); thread1.start(); latch.await(); if (x == 0 && y == 0) { String result = "第" + i + "次"; System.out.printf(result); break; } } } }