java多线程笔记--lock多线程计数

叁歲伎倆 2022-01-29 11:57 246阅读 0赞

# java多线程笔记–lock多线程计数 #

### 文章目录 ###

*  java多线程笔记--lock多线程计数
 *   *   *  1.lock多线程计数

lock：主要有可重入锁，读写锁，文件锁

### 1.lock多线程计数 ###

package com.ctg.test.lock;
    
    import java.util.concurrent.CountDownLatch;
    import java.util.concurrent.locks.ReentrantLock;
    
    /**
     * @Description: Lock解决多线程访问相同的资源
     * lock的特性：
     * 1）相比于 synchronized隐式获取、释放锁，lock需要显示的获取释放锁
     * 2）相比于 synchronized，lock可以可中断的获取锁及超时获取锁，
     * 3）ReentrantLock，同一个线程调用lock方法，可以连续多次获取锁而不被阻塞
     * @Author: 
     * @Date: 2019/5/12 0:05
     */
    public class TestLockCount {
        private  static  int num =0;
        private  static ReentrantLock lock = new ReentrantLock();
        public static void main(String[] args)throws InterruptedException {
            for(int k=0;k<100;k++){
                CountDownLatch countDownLatch = new CountDownLatch(3);
                num=0;
                Thread t1 =new Thread(new CountRunnable(countDownLatch));
                Thread t2 =new Thread(new CountRunnable(countDownLatch));
                Thread t3 =new Thread(new CountRunnable(countDownLatch));
                t1.start();
                t2.start();
                t3.start();
                countDownLatch.await();
                System.out.println("第"+(k+1)+"次计算结果，num=" + num);
            }
        }
    
        public static  class CountRunnable implements Runnable{
            private CountDownLatch countDownLatch;
            CountRunnable (CountDownLatch countDownLatch){
                this.countDownLatch=countDownLatch;
            }
            @Override
            public void run() {
                lock.lock();
                try{
                    for (int i=0;i<10000;i++){
                        num=num+1;
                        // System.out.println(Thread.currentThread().getName()+":"+num);
                    }
                }
                finally {
                    lock.unlock();
                }
                countDownLatch.countDown();
            }
        }
    }

执行100次结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3loaHloaHloaHloaA_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3loaHloaHloaHloaA_size_16_color_FFFFFF_t_70]: /images/20220129/1e5aa9c69c6543b592740b4a42712144.png