import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;public class SemaphoreTest {private static final int THREAD_COUNT = 30;private static ExecutorService threadPool = Executors.newFixedThreadPool(THREAD_COUNT);private static Semaphore s = new Semaphore(10);public static void main(String[] args) {for (int i = 0; i < THREAD_COUNT; i++) {threadPool.execute(new Runnable() {@Overridepublic void run() {try {s.acquire();System.out.println(Thread.currentThread().getName());Thread.sleep(5000);System.out.println("--------------");s.release();} catch (InterruptedException e) {}}});}threadPool.shutdown();}
}

import java.util.concurrent.CountDownLatch;public class CountDownLatchTest2 {public static void main(String[] args) {// 创建计数器，初始化为2final CountDownLatch latch = new CountDownLatch(2);new Thread(() -> {try {System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");Thread.sleep(3000);System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");latch.countDown();// 减一} catch (InterruptedException e) {e.printStackTrace();}}).start();new Thread(() -> {try {System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");Thread.sleep(3000);System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");latch.countDown();} catch (InterruptedException e) {e.printStackTrace();}}).start();try {System.out.println("等待2个子线程执行完毕...");// 阻塞
            latch.await();System.out.println("2个子线程已经执行完毕");System.out.println("继续执行主线程");} catch (InterruptedException e) {e.printStackTrace();}}
}

public void test()
{/*** 创建一个限流器，设置每秒放置的令牌数：2个。速率是每秒可以2个的消息。* 返回的RateLimiter对象可以保证1秒内不会给超过2个令牌，并且是固定速率的放置。达到平滑输出的效果*/RateLimiter r = RateLimiter.create(2);while (true){/*** acquire()获取一个令牌，并且返回这个获取这个令牌所需要的时间。如果桶里没有令牌则等待，直到有令牌。* acquire(N)可以获取多个令牌。*/System.out.println(r.acquire());}
}

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=2r/s;
server { location / { limit_req zone=mylimit;
    }
}