通过CAS避免加锁

package com.guo.day05;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * Created by guo on 2017/6/3.
 */
public class Seqience {
    //    通过加锁防止互斥
    private int value;
    public synchronized int next1(){
        return value++;
    }

    private AtomicInteger count =new AtomicInteger(0);
    private int next2(){
//        循环保证compareAndSet一直进行
//        ABA问题的解决 添加了版本值
        while(true){
            int current = count.get();//读取内存中的值
            int next = current+1;
            //compareAndSet硬件指令一定是原子操作  比较内存的值和现在的值是否有变化
            if(count.compareAndSet(current,next)){
                return next;
            }
        }
    }
}