java中的并发工具类---大秦帝国篇

目录

 

java中的并发工具类

1、CountDownLatch的使用

2、CyclicBarrier

3、Semaphore

4、Exchanger


java中的并发工具类

java中的并发工具类
序号 工具类 匹配的业务场景
1 CountDownLatch 统一服务
2 CyclicBarrier 统一命令
3 Semaphore 流量控制
4 Exchanger 线程之间交换数据

 如果我们把线程比作人,那么线程之间的协作其实就是人类之间的协作。 而人类之间的协作会有以下几种情况:

1、统一服务:你们都完成一件事情后我再继续完成另一件事情;     典型的例子:几个人一起去吃饭,人齐了哈,服务员上菜!(也有不仗义的,自己去了就先吃,这种不在协作之列)

该场景对应CountDownLatch的使用场景!

2、统一命令:大家等待我的命令后统一行动;  典型的例子:打仗镜头里边,长官一声令下,打!

该场景对应CyclicBarrier的使用场景!

3、商量好:采取行动之前需要商量好,互相交换信息;   典型的例子约会(下班后一起去吃刷羊肉):A: 亲爱的我们在晓月楼门口见,我刚下班。   B:好的,稍等,马上到。

该场景对应Exchanger的使用场景!

4、狼多肉少吃不饱:需要限制获取资源的人数;  典型的例子就是北京摇车牌,数据库连接池中限制数据库的连接的个数等。

该场景对应Semaphore的使用场景!

1、CountDownLatch的使用

测试代码

package com.miller.fanxing;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;

/*
 * author :振彪(miller)
 * data :2021-01-10
 * des: test how to use CountDownLatch
 * */
public class CountDownLatchTest {
    //CountDownLatch构造器接收一个int类型的参数作为计数器,如果你想等待n个点完成,这里就传入n
    private static CountDownLatch countDownLatch = new CountDownLatch(6);
    private static ConcurrentHashMap map = new ConcurrentHashMap();

    public static void main(String[] args) throws InterruptedException {
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("韩国被灭");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("魏国被灭");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("赵国被灭");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("楚国被灭");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("燕国被灭");
                countDownLatch.countDown();
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("齐国被灭");
                countDownLatch.countDown();
            }
        }).start();
        countDownLatch.await();
        System.out.println("六国被灭,天下一统!");
    }
}

测试结果:

韩国被灭
魏国被灭
赵国被灭
楚国被灭
燕国被灭
齐国被灭
六国被灭,天下一统!

结论:在其它线程执行之前主线程一直等待。六国都灭亡,即其它线程都执行完毕,秦国一统天下,就是主线程开始执行。

 

2、CyclicBarrier

测试代码

package com.miller.fanxing;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CyclicBarrier;

/*
 * author :冯振彪(miller)
 * data :2021-01-10
 * des: test how to use CyclicBarrier
 * */
public class CyclicBarrierTest {
    //合众讨伐秦国,6过军队集合于函谷关前,只有6国军队都到齐才能开战
    private static CyclicBarrier cyclicBarrier = new CyclicBarrier(6);

    private static ConcurrentHashMap map = new ConcurrentHashMap();

    private static StringBuffer taoFanBaoQin = new StringBuffer("");

    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    System.out.println("齐国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("齐国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }

            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                map.put("魏国",1);
                try {
                    System.out.println("魏国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("魏国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                map.put("韩国",1);
                try {
                    System.out.println("韩国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("韩国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }

            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                map.put("燕国",1);
                try {
                    System.out.println("燕国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("燕国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }

            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                map.put("楚国",1);
                try {
                    System.out.println("楚国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("楚国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }

            }
        }).start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                map.put("赵国",1);
                try {
                    System.out.println("赵国军队到达函谷关");
                    cyclicBarrier.await();
                    taoFanBaoQin.append("赵国会盟,");
                    System.out.println("六国齐聚,对秦开战!" + taoFanBaoQin.toString());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }
        }).start();

    }

}

测试结果:

 齐国军队到达函谷关
魏国军队到达函谷关
韩国军队到达函谷关
燕国军队到达函谷关
楚国军队到达函谷关
赵国军队到达函谷关
六国齐聚,对秦开战!齐国会盟,魏国会盟,
六国齐聚,对秦开战!齐国会盟,魏国会盟,韩国会盟,
六国齐聚,对秦开战!齐国会盟,魏国会盟,韩国会盟,燕国会盟,
六国齐聚,对秦开战!齐国会盟,魏国会盟,
六国齐聚,对秦开战!齐国会盟,魏国会盟,韩国会盟,燕国会盟,楚国会盟,
六国齐聚,对秦开战!齐国会盟,魏国会盟,韩国会盟,燕国会盟,楚国会盟,赵国会盟,

结论:六国军队都到达函谷关之前没有举行会盟。 线程运行至

cyclicBarrier.await()方法时会等待其它线程执行。

3、Semaphore

测试代码:

package com.miller.fanxing;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicInteger;

/*
 * author :冯振彪(miller)
 * data :2021-01-10
 * des: test how to use Semaphore
 * */
public class SemaphoreTest {
    private static final int THREAD_COUNT = 30;
    //30个线程参与竞争:30个诸侯觐见周天子
    private static ExecutorService threadPool = Executors.newFixedThreadPool(30);

    //周天子每天只能见10个诸侯
    private static Semaphore s = new Semaphore(10);  //流量控制

    private static AtomicInteger j = new AtomicInteger();

    public static void main(String[] args) {
        for (int i = 0; i < THREAD_COUNT ; i ++) {
            threadPool.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        s.acquire();
                        System.out.println("第" + j +"个诸侯觐见周天子!");
                        j.addAndGet(1);
                        //s.release();   //故意不释放,第二天才能见其它10诸侯,第三天才能见最后10个诸侯
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }
            });
        }
        threadPool.shutdown();
    }
}

测试结果:

第0个诸侯觐见周天子!
第1个诸侯觐见周天子!
第2个诸侯觐见周天子!
第3个诸侯觐见周天子!
第4个诸侯觐见周天子!
第5个诸侯觐见周天子!
第6个诸侯觐见周天子!
第7个诸侯觐见周天子!
第8个诸侯觐见周天子!
第9个诸侯觐见周天子!

结论: 多个使用者竞争有限个资源时做流量控制非常好!

4、Exchanger

测试代码

package com.miller.fanxing;

import java.util.concurrent.Exchanger;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/*
* author :振彪(miller)
* data :2021-01-10
* despetion: test how to use exchanger
* */
public class ExchangerTest {

    private static final Exchanger exchanger = new Exchanger();

    private static final ExecutorService threadPool = Executors.newFixedThreadPool(2);

    public static void main(String[] args) {
        threadPool.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    String QuLing = "求贤令";
                    String B = exchanger.exchange(QuLing);
                    System.out.println("QuLing:" + QuLing);
                    System.out.println("B:" + B);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });

        threadPool.execute(new Runnable() {
            @Override
            public void run() {
                try {
                    String weiYang = "商鞅变法";
                    String A = exchanger.exchange(weiYang);
                    System.out.println("weiYang:" + weiYang);
                    System.out.println("A:" + A);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        threadPool.shutdown();
    }
}

测试结果:
QuLing:求贤令
B:商鞅变法
weiYang:商鞅变法
A:求贤令

结论:Exchanger可以在线程之间传递消息!

 

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