使用CAS实现的非阻塞计数器

//使用CAS实现的非阻塞计数器public class CasCount {private SimulatedCAS value;public int getValue(){return value.get();}public int increment(){int v;do{v = value.get();}while(v != value.compareAndSwap(v, v + 1));return v + 1;}}

//模拟CAS操作public class SimulatedCAS {private int value;public synchronized int get(){return value;}public synchronized int compareAndSwap(int expectedValue,int newValue){int oldValue = value;if(oldValue == expectedValue){value = newValue;}return oldValue;}public synchronized boolean compareAndSet(int expectedValue,int newValue){return (expectedValue == compareAndSwap(expectedValue, newValue));}}

import java.util.Random;import java.util.concurrent.atomic.AtomicInteger;public class CASTest {public static void main(String[] args) {Count1 c1 = new Count1();for(int i=0; i<2; i++){new Thread(c1).start();}}}//Lock-Free算法,不需要加锁,通常都是由三个部分组成class Count1 implements Runnable{private AtomicInteger max = new AtomicInteger();public void set(int value){while(true){//1、循环int current = max.get();if(value != current){//满足一定的条件,则进行设置值try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("当前值:"+max.get()+"#"+current);if(max.compareAndSet(current, value)){//2、CAS(CompareAndSet)break;//3、回退}else{System.out.println("---------------------------重新比较");continue;}}else{break;}}}public int getMax(){return max.get();}final Random rand = new Random();@Overridepublic void run() {for(int j=0; j<200; j++){int i = rand.nextInt(100+5);System.out.println(Thread.currentThread().getName()+"#设置:"+i);set(i);System.out.println(Thread.currentThread().getName()+"#取得:"+getMax());}}}//使用锁机制来进行同步class Count2{private volatile int max = 0;public synchronized void set(int value){if(value > max){max = value;}}public int getMax(){return max;}}