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

Process finished with exit code 0