package concurrent;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

/**
 * Auth: zhouhongliang
 * Date：2019/8/1
 * 并发限流功能
 * Semaphore
 */
public class SemaphoreDemo {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newCachedThreadPool();
        Semaphore semaphore = new Semaphore(3);
        for (int i = 0; i < 10; i++) {
            executorService.execute(() -> {
                try {
                    //semaphore.acquire();//一直等待
                    if (semaphore.tryAcquire(3, TimeUnit.SECONDS)) {//等待3秒
                        play();
                        semaphore.release();
                    } else {
                        System.out.println(Thread.currentThread().getName() + " 进入超时");
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {

                }
            });
        }
        executorService.shutdown();
    }

    /**
     * 模拟任务
     */
    public static void play() {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        System.out.println(simpleDateFormat.format(new Date()) + " " + Thread.currentThread().getName() + " 进入");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(simpleDateFormat.format(new Date()) + " " + Thread.currentThread().getName() + " 退出");
    }
}

输出结果：
2019-08-01 11:09:50 pool-1-thread-1 进入
2019-08-01 11:09:50 pool-1-thread-3 进入
2019-08-01 11:09:50 pool-1-thread-2 进入
2019-08-01 11:09:52 pool-1-thread-3 退出
2019-08-01 11:09:52 pool-1-thread-1 退出
2019-08-01 11:09:52 pool-1-thread-2 退出
2019-08-01 11:09:52 pool-1-thread-4 进入
2019-08-01 11:09:52 pool-1-thread-5 进入
2019-08-01 11:09:52 pool-1-thread-6 进入
pool-1-thread-7 进入超时
pool-1-thread-8 进入超时
pool-1-thread-9 进入超时
pool-1-thread-10 进入超时
2019-08-01 11:09:54 pool-1-thread-6 退出
2019-08-01 11:09:54 pool-1-thread-5 退出
2019-08-01 11:09:54 pool-1-thread-4 退出

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Process finished with exit code 0

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