网站中英切换实例,wordpress标题相关,昆山便宜做网站,网络哪个公司好ABA问题#xff1a;
假如有两个线程1#xff0c;2#xff1b; cas下#xff1a;1.线程取值完等待#xff0c;2线程取值并把A改成B#xff0c;有把B改成A#xff0c;这是1线程执行会任务A还是原来的A没有发生改变#xff0c;如果不在乎中间结果#xff0c;只看收尾
假如有两个线程12 cas下1.线程取值完等待2线程取值并把A改成B有把B改成A这是1线程执行会任务A还是原来的A没有发生改变如果不在乎中间结果只看收尾那么没必要解决ABA问题
如何解决
使用AtomicStampedRefererce加版本号
代码演示如下
package Volatile;import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;/*** ABA问题的解决办法 AtomicStampedReference 时间戳原子引用·*/
public class ABA {static AtomicReferenceInteger atomicReference new AtomicReference(100);static AtomicStampedReferenceInteger atomicStampedReference new AtomicStampedReference(100,1);public static void main(String []args){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(()-{//暂停1秒t2线程保证t1完成一次ABAtry {TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace();}System.out.println(atomicReference.compareAndSet(100,2019)\tatomicReference.get());},t2).start();try {TimeUnit.SECONDS.sleep(2); } catch (InterruptedException e) { e.printStackTrace();}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第一次版本号atomicStampedReference.getStamp());//暂停1秒t3线程,让t4也获取到一样的stamptry {TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace();}atomicStampedReference.compareAndSet(100,101,atomicStampedReference.getStamp(),atomicStampedReference.getStamp()1);System.out.println(Thread.currentThread().getName()\t第二次版本号atomicStampedReference.getStamp());atomicStampedReference.compareAndSet(101,100,atomicStampedReference.getStamp(),atomicStampedReference.getStamp()1);System.out.println(Thread.currentThread().getName()\t第三次版本号atomicStampedReference.getStamp());},t3).start();new Thread(()-{int stamp atomicStampedReference.getStamp();System.out.println(Thread.currentThread().getName()\t第一次版本号atomicStampedReference.getStamp());//暂停1秒t3线程try {TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace();}boolean result atomicStampedReference.compareAndSet(100, 2019, stamp, stamp 1);System.out.println(Thread.currentThread().getName()\t修改功否result);System.out.println(Thread.currentThread().getName()\t当前实际最新值atomicStampedReference.getReference());},t4).start();}
}
