Java Exchanger

http://mouselearnjava.iteye.com/blog/1921947

本文介绍Exchanger工具类, 然后采用Exchanger给出一个两个线程交换数值的简单实例。

Exchanger介绍

Java代码 收藏代码

/**  
  * A synchronization point at which two threads can exchange objects. 
  * Each thread presents some object on entry to the {@link #exchange 
  * exchange} method, and receives the object presented by the other 
  * thread on return.

    */

从上面的注释中可以看出: Exchanger提供了一个同步点,在这个同步点,两个线程可以交换数据。每个线程通过exchange()方法的入口提供数据给另外的线程,并接收其它线程提供的数据,并返回。

Exchanger通过Lock和Condition来完成功能,Exchanger的一个重要的public方法是exchange方法,用于线程的数据交换,

Exchanger工具类的使用案例

本文给出一个简单的例子,实现两个线程之间交换数据,用Exchanger来做非常简单。

Java代码收藏代码

package my.concurrent.exchanger;

import java.util.concurrent.Exchanger;

import java.util.concurrent.atomic.AtomicReference;

public class ThreadA implements Runnable {

private final Exchanger<Integer> exchanger;  

private final AtomicReference<Integer> last = new AtomicReference<Integer>(  
        5);  

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

public void run() {  
    try {  
        while (true) {  
            last.set(exchanger.exchange(last.get()));  
            System.out.println(" After calling exchange. Thread A has value: " + last.get());  
            Thread.sleep(2000);  
        }  
    } catch (InterruptedException e) {  
        e.printStackTrace();  
    }  
}

}

Java代码收藏代码

package my.concurrent.exchanger;

import java.util.concurrent.Exchanger;

import java.util.concurrent.atomic.AtomicReference;

public class ThreadB implements Runnable {

private Exchanger<Integer> exchanger;  

private final AtomicReference<Integer> last = new AtomicReference<Integer>(  
        10);  

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

public void run() {  
    try {  
        while (true) {  
            last.set(exchanger.exchange(last.get()));  
            System.out.println(" After calling exchange. Thread B has value: " + last.get());  
            Thread.sleep(2000);  
        }  
    } catch (InterruptedException e) {  
        e.printStackTrace();  
    }  
}

}

Java代码收藏代码

package my.concurrent.exchanger;

import java.util.concurrent.Exchanger;

public class ExchangerTest {

public static void main(String[] args) {  
    Exchanger<Integer> exchanger = new Exchanger<Integer>();  
    new Thread(new ThreadA(exchanger)).start();  
    new Thread(new ThreadB(exchanger)).start();  
}

}

Contents

Java Exchanger