• i++的线程不安全以及使用原子类保证线程安全


    package com.xiangwen.day3;
    
    import java.util.concurrent.CountDownLatch;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.atomic.AtomicBoolean;
    import java.util.concurrent.atomic.AtomicInteger;
    
    public class AtomicTest {
        public static void main(String[] args) {
    //        AtomicBoolean atomicFlg=new AtomicBoolean(false);
    //        boolean res=atomicFlg.compareAndSet(false,true);
    //        System.out.println(res);
    //        System.out.println(atomicFlg);
    //
    //        AtomicInteger atomicInt=new AtomicInteger();
    //        boolean res2=atomicInt.compareAndSet(10,123);
    //        System.out.println(res2);
    //        System.out.println(atomicInt);
    //        Integer a=0;
    //        atomicInt.addAndGet(2);
            UnsafeCounter UnsafeCounter=new UnsafeCounter();
             CountDownLatch c1=new CountDownLatch(200);
            ExecutorService executorService = Executors.newCachedThreadPool();
    
            for(int i=0;i<200;i++){
                new Thread(new ThreadTestInt(UnsafeCounter)).start();
                c1.countDown();
          }
            try {
               c1.await();
               Thread.sleep(1000);
               System.out.println("=======UnsafeCounter:"+UnsafeCounter.get());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
    //使用线程安全的原子类
        SafeCounter safeCounter=new SafeCounter();
        CountDownLatch c2=new CountDownLatch(200);
            for(int j=0;j<200;j++){
            new Thread(new ThreadTestAtomicInt(safeCounter)).start();
            c2.countDown();
        }
            try {
            c2.await();
            Thread.sleep(1000);
            System.out.println("=======safeCounter:"+safeCounter.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
    }
        class ThreadTestInt implements Runnable{
            private UnsafeCounter unsafeCounter;
            public ThreadTestInt(UnsafeCounter unsafeCounter) {
                this.unsafeCounter = unsafeCounter;
            }
            @Override
            public void run() {
                unsafeCounter.add();
            }
        }
    class ThreadTestAtomicInt implements Runnable{
        private SafeCounter safeCounter;
        public ThreadTestAtomicInt(SafeCounter safeCounter) {
            this.safeCounter = safeCounter;
        }
        @Override
        public void run() {
            safeCounter.add();
        }
    }
    class UnsafeCounter {
        public int count = 0;
        public void add() {//没有加同步sychronized
            if(count%2==0){//for循环开启200个线程,因为i++运行很快,相当于顺序运行了,这样让线程稍微休眠,等其他线程创建出来竞争cpu
                try {
                    Thread.sleep(5);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            count++;
        }
        public int get() {
            return count;
        }
    
    }
    class SafeCounter {
        public AtomicInteger count = new AtomicInteger(0);
        public void add() {
            if(count.get()%2==0){//for循环开启200个线程,因为i++运行很快,相当于顺序运行了,这样让线程稍微休眠,等其他线程创建出来竞争cpu
                try {
                    Thread.sleep(5);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            count.addAndGet(1);
        }
        public int get() {
            return count.get();
        }
    
    }
  • 相关阅读:
    980不同路径III
    输入函数
    IDEA更新maven依赖包
    join()函数
    方差偏差困境
    np.bincount()函数
    72编辑距离
    741摘樱桃
    523连续的子数组和
    1306跳跃游戏III
  • 原文地址:https://www.cnblogs.com/wenwenzuiniucha/p/14807642.html
Copyright © 2020-2023  润新知