線程安全之原子性操作CAS

原子性

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• 1.競態條件與臨界區

package com.yulang.threadpool.thread;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class LockTest {

    private volatile AtomicInteger i=new AtomicInteger();
    public void add(){
        i.incrementAndGet();
    }

    public static void main(String[] args) throws InterruptedException {
        LockTest lockTest = new LockTest();
        for(int j=0;j<2;j++){
            new Thread(()->{
                for(int i=0;i<10000;i++){
                    lockTest.add();
                }
            }).start();
        }
        TimeUnit.SECONDS.sleep(2);
        System.out.println(lockTest.i);
    }

}

java8新增的效率更高,採用的是分佈式計算方式

package com.yulang.threadpool.thread;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.LongAdder;

public class LockTest {

    private volatile LongAdder i=new LongAdder();
    public synchronized void add(){
        i.increment();
    }

    public static void main(String[] args) throws InterruptedException {
        LockTest lockTest = new LockTest();
        for(int j=0;j<2;j++){
            new Thread(()->{
                for(int i=0;i<10000;i++){
                    lockTest.add();
                }
            }).start();
        }
        TimeUnit.SECONDS.sleep(2);
        System.out.println(lockTest.i);
    }

}