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解决ABA问题的代码示例
/**
* 解决CAS的ABA问题
*/
public class SolveABAOfCAS {
static AtomicReference<Integer> atomicReference = new AtomicReference<>(100); static AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1); public static void main(String[] args) throws InterruptedException { System.out.println("==========以下是ABA问题的产生=========="); new Thread(() -> { atomicReference.compareAndSet(100, 101); atomicReference.compareAndSet(101, 100); }, "t1").start(); new Thread(() -> { try { // 暂停1秒钟,保证上面完成一次ABA操作 Thread.sleep(1000); System.out.println(atomicReference.compareAndSet(100, 2019) + "\t" + atomicReference.get()); } catch (InterruptedException e) { e.printStackTrace(); } }, "t2").start(); Thread.sleep(2000); System.out.println("==========以下是ABA问题的解决=========="); new Thread(() -> { int stamp = atomicStampedReference.getStamp(); System.out.println(Thread.currentThread().getName() + "\t第1次版本号" + stamp); try { // 暂停一秒钟t3线程 Thread.sleep(1000); atomicStampedReference.compareAndSet(100, 101, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1); System.out.println(Thread.currentThread().getName() + "\t第2次版本号" + atomicStampedReference.getStamp()); atomicStampedReference.compareAndSet(101, 100, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1); System.out.println(Thread.currentThread().getName() + "\t第3次版本号" + atomicStampedReference.getStamp()); } catch (InterruptedException e) { e.printStackTrace(); } }, "t3").start(); new Thread(() -> { int stamp = atomicStampedReference.getStamp(); System.out.println(Thread.currentThread().getName() + "\t第1次版本号" + stamp); try { // 暂停3秒钟t4线程,保证上面的t3线程完成一次ABA操作 Thread.sleep(3000); boolean result = atomicStampedReference.compareAndSet(100, 2019, stamp, stamp + 1); System.out.println(Thread.currentThread().getName() + "\t修改成功否: " + result + "\t当前最新实际版本号: " + atomicStampedReference.getStamp()); System.out.println(Thread.currentThread().getName() + "\t当前实际最新值: " + atomicStampedReference.getReference()); } catch (InterruptedException e) { e.printStackTrace(); } }, "t4").start(); } }