測試AtomicInteger的可見性、有序性、原子性

package com.dwz.atomic;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * AtomicInteger
 * 可見性
 * 有序性
 * 原子性
 */
public class AtomicIntegerTest {
    public static void main(String[] args) throws InterruptedException {
        Set<Integer> set = Collections.synchronizedSet(new HashSet<Integer>());
        AtomicInteger value = new AtomicInteger();
        Thread t1 = new Thread() {
            @Override
            public void run() {
                int x = 0;
                while(x < 500) {
                    int v = value.getAndIncrement();
                    set.add(v);
                    System.out.println(Thread.currentThread().getName() + ":" + v);
                    x++;
                }
            }
        };
        
        Thread t2 = new Thread() {
            @Override
            public void run() {
                int x = 0;
                while(x < 500) {
                    int v = value.getAndIncrement();
                    set.add(v);
                    System.out.println(Thread.currentThread().getName() + ":" + v);
                    x++;
                }
            }
        };
        
        Thread t3 = new Thread() {
            @Override
            public void run() {
                int x = 0;
                while(x < 500) {
                    int v = value.getAndIncrement();
                    set.add(v);
                    System.out.println(Thread.currentThread().getName() + ":" + v);
                    x++;
                }
            }
        };
        
        t1.start();
        t2.start();
        t3.start();
        
        t1.join();
        t2.join();
        t3.join();
        
        System.out.println(set.size());
    }
}

 總結：

1.volatile修飾的變量可以保證可見性和有序性
2.CAS算法，也就是CPU級別的同步指令，相當於樂觀鎖，它可以測到其他線程對共享數據的變化情況