高并发常用辅助类

高并发常用辅助类

7.1 CountDownLatch

减法计数器

countDownLatch.countDown();//数量-1

countDownLatch.await();//等到计数器归零，再向下执行

package com.liu.add;

import java.util.concurrent.CountDownLatch;

//计数器
public class CountDownLatchTest {
    public static void main(String[] args) throws InterruptedException {

        CountDownLatch countDownLatch = new CountDownLatch(6);
        for (int i = 1; i <= 6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" go out");
                countDownLatch.countDown();//数量-1
            },String.valueOf(i)).start();
        }

        countDownLatch.await();//等到计数器归零，再向下执行

        System.out.println("close!");
    }
}

7.2 CyclicBarrier

cyclicBarrier.await();//等待计数器变成7

加法计数器

package com.liu.add;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class CyclicBarrierTest {
    public static void main(String[] args) {
        CyclicBarrier cyclicBarrier = new CyclicBarrier(7,()->{
            System.out.println("成功");
        });
        for (int i = 1; i <= 7; i++) {
            final int temp = i;
            //lambda表达式拿不到i，所以定义一个中间变量
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" 收集 "+ temp +" 个");
                try {
                    cyclicBarrier.await();//等待计数器变成7
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

7.3 Semaphore

信号灯

semaphore.acquire();获得，如果已经满了，等待，等待被释放完为止

semaphore.release();//释放，会将当前的信号量释放+1，然后唤醒等待的线程

作用：多个共享资源互斥的使用，并发限流，控制最大的线程数。

package com.liu.add;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

public class SemaphoreTest {

    public static void main(String[] args) {
        //限流
        Semaphore semaphore = new Semaphore(3);

        for (int i = 1; i <= 6; i++) {
            new Thread(()->{
                //acquire() 得到
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()+" 抢到");
                    TimeUnit.SECONDS.sleep(2);
                    System.out.println(Thread.currentThread().getName()+" 离开");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    semaphore.release();//释放
                }
            },String.valueOf(i)).start();
        }

    }


}