併發工具使用【CountDownLatch,CyclicBarrier】--代碼示例

 1.CountDownLatch 的使用

 

應用場景：

等待已知數量的線程執行完後 ，在喚醒當前的主線程的應用場景，比如：查詢所有航空公司的機票，多個線程單獨執行查詢單個航空公司的機票，所有的單個線程結束後，環境主線程，將結果輸出。

相當於計數器進行減的操作

 

實例代碼：

package com.lhj;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

public class CountDownLatchDemo {

    //針對航班查詢進行舉例

    private static List<String> company = Arrays.asList("東方航空", "南方航空", "海南航空");
    private static List<String> fightList = new ArrayList<>();

    public static void main(String[] args) throws InterruptedException {

        String origin = "PEK";

        String dest = "pvg";

        Thread[] threads = new Thread[company.size()];


        CountDownLatch countDownLatch = new CountDownLatch(company.size());

        for (int i = 0; i < threads.length; i++) {
            final String companyName = company.get(i);

            threads[i] = new Thread(() -> {
                System.out.println(companyName + "查詢飛機票從"+origin+"到" + dest);

                //隨機產生票數
                int paperNum = new Random().nextInt(10);

                try {
                    TimeUnit.SECONDS.sleep(paperNum);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                fightList.add(companyName + "--" + paperNum);
                System.out.printf("%s公司查詢成功！\n", companyName);
                countDownLatch.countDown();
            });

            threads[i].start();

        }

        countDownLatch.await();
        System.out.println("==============查詢結果如下：================");
        fightList.forEach(System.out::println);

    }


}

運行結果

2.CyclicBarrier的使用

應用場景：

等待所有線程開啓完成後，喚醒主線程，例如

等該所有參賽的運動員參賽全部到位後，開始比賽

相當於計數器進行加的操作

示例代碼：

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

public class CyclicBarrierDemo {


    public static void main(String[] args) {


        Thread[] running = new Thread[8];

        CyclicBarrier cyclicBarrier = new CyclicBarrier(running.length);


        for (int i = 0; i < running.length; i++) {
            running[i] = new Thread(() -> {
                try {
                    TimeUnit.SECONDS.sleep(new Random().nextInt(10));
                    System.out.println(Thread.currentThread().getName() + "準備好了！");
                    cyclicBarrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }

                System.out.println("選手" + Thread.currentThread().getName() + "起跑");
            }, "player" + i);

            running[i].start();
        }

    }
}

運行結果：