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前几天在公司的项目上有个同事使用了多线程统计数据，当时出现了一个用户一直使用服务器首次登录信息作为查询信息。找了半天才发现，线程池资源同步了。后面手动将数据set进去的。

等待线程全部执行完毕，这里使用的是减法计数器，也可而已用加法计数器：CyclicBarrier

package com.quxiao.controller;import java.util.*;
import java.util.concurrent.*;
import java.util.stream.Collectors;/*** @program: package1* @author: quxiao* @create: 2023-09-27 15:22**/
public class t3 {static final ExecutorService service = Executors.newFixedThreadPool(10);public static void main(String[] args) throws ExecutionException, InterruptedException {CountDownLatch countDownLatch = new CountDownLatch(4);FutureTask task1 = new FutureTask<>(new t(2, countDownLatch));FutureTask task2 = new FutureTask<>(new t(3, countDownLatch));FutureTask task3 = new FutureTask<>(new t(4, countDownLatch));FutureTask task4 = new FutureTask<>(new t(5, countDownLatch));service.execute(task1);service.execute(task2);service.execute(task3);service.execute(task4);countDownLatch.await();System.out.println(task1.get());System.out.println(task2.get());System.out.println(task3.get());System.out.println(task4.get());
//        service.shutdown();}static class t implements Callable<List<Integer>> {List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);int sum = 0;CountDownLatch countDownLatch;public t(int sum, CountDownLatch countDownLatch) {this.sum = sum;this.countDownLatch = countDownLatch;}@Overridepublic List<Integer> call() throws Exception {TimeUnit.SECONDS.sleep(1L);List<Integer> returnList = list.stream().filter(x -> x >= sum).collect(Collectors.toList());countDownLatch.countDown();return returnList;}}
}

限流操作，限制人数访问，超过预定值就等待：

package com.quxiao.controller;import java.util.*;
import java.util.concurrent.*;
import java.util.stream.Collectors;/*** @program: package1* @author: quxiao* @create: 2023-09-27 15:22**/
public class t3 {static final ExecutorService service = Executors.newFixedThreadPool(10);public static void main(String[] args) throws ExecutionException, InterruptedException {Semaphore semaphore = new Semaphore(3);for (int i = 0; i < 9; i++) {final int t = i;new Thread(() -> {try {semaphore.acquire();TimeUnit.SECONDS.sleep(5L);System.out.println(Thread.currentThread().getName() + "进来了");System.out.println(Thread.currentThread().getName() + "出去了");System.out.println();} catch (InterruptedException e) {throw new RuntimeException(e);} finally {semaphore.release();}}, "" + i).start();}}
}