Java 併發編程學習筆記(6) ----Exchanger

Exchanger 的使用

1.exchange() 方法阻塞的特點

此方法被調用後等待其他線程來取得數據，如果沒有其他線程取得數據，則一直阻塞等待。

代碼

package com.lhc.concurrent.exchanger.exchange;

import java.util.concurrent.Exchanger;

public class ThreadA extends Thread {
    private Exchanger<String> exchanger;

    public ThreadA(Exchanger<String> exchanger) {
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        try {
            System.out.println("在線程A中得到線程B的值=" + exchanger.exchange("Chinese A"));
            System.out.println("A end");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

測試類

package com.lhc.concurrent.exchanger.exchange;

import java.util.concurrent.Exchanger;

public class BlockTest {
    public static void main(String[] args){
        Exchanger<String> exchanger = new Exchanger<>();
        Thread a = new ThreadA(exchanger);
        a.start();
        System.out.println("main end");
    }
}

測試結果

main end

當沒有其他線程來調用時，會阻塞當前線程。

2.exchange() 方法傳遞數據

此方法也可以在不同線程之間傳遞數據

添加代碼

package com.lhc.concurrent.exchanger.exchange;

import java.util.concurrent.Exchanger;

public class ThreadB extends Thread{
    private Exchanger<String> exchanger;

    public ThreadB(Exchanger<String> exchanger) {
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        try {
            System.out.println("在線程B中得到線程A的值=" + exchanger.exchange("Chinese B"));
            System.out.println("B end");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

修改測試代碼如下：

package com.lhc.concurrent.exchanger.exchange;

import java.util.concurrent.Exchanger;

public class BlockTest {
    public static void main(String[] args){
        Exchanger<String> exchanger = new Exchanger<>();
        Thread a = new ThreadA(exchanger);
        Thread b = new ThreadB(exchanger);
        a.start();
        b.start();
        System.out.println("main end");
    }
}

測試結果

main end

在線程B中得到線程A的值=Chinese A

B end

在線程A中得到線程B的值=Chinese B

A end

3.exchange() 方法設置超時時間

exchange(V v,long timeout,TimeUnit unit) 方法在指定的時間沒有其他線程獲取數據，則出現超時異常