J.U.C工具包之Exchanger

技术2020年8月4日

什么是Exchanger：

两个线程达到同步点后，相互交换数据，提供一个同步点，在这个同步点两个数据可以交换数据。

一个线程到达同步点会先被阻塞，直到另外一个线程到达同步点为止。

只能用于两个线程交换数据。

例子：

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

public class ExchangerDemo {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        Exchanger<String> exchanger = new Exchanger<String>();
        executorService.execute(() -> {
            try {
                String fromAnothorThread =
                    exchanger.exchange("This is :" + Thread.currentThread().getName() + " do u copy?");
                System.out.println(Thread.currentThread().getName() + " got message :" + fromAnothorThread);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
        executorService.execute(() -> {
            try {
                System.out.println("waiting 1 seconds to exchange");
                Thread.sleep(1000);
                String fromAnothorThread =
                    exchanger.exchange("This is :" + Thread.currentThread().getName() + " copy that!");
                System.out.println(Thread.currentThread().getName() + " got message :" + fromAnothorThread);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });
    }
}

import java.util.concurrent.Exchanger;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

public class ExchangerDemo {

public static void main(String[] args) {

ExecutorService executorService = Executors.newFixedThreadPool(2);

Exchanger<String> exchanger = new Exchanger<String>();

executorService.execute(() -> {

try {

String fromAnothorThread =

exchanger.exchange("This is :" + Thread.currentThread().getName() + " do u copy?");

System.out.println(Thread.currentThread().getName() + " got message :" + fromAnothorThread);

} catch (InterruptedException e) {

e.printStackTrace();

}

});

executorService.execute(() -> {

try {

System.out.println("waiting 1 seconds to exchange");

Thread.sleep(1000);

String fromAnothorThread =

exchanger.exchange("This is :" + Thread.currentThread().getName() + " copy that!");

System.out.println(Thread.currentThread().getName() + " got message :" + fromAnothorThread);

} catch (InterruptedException e) {

e.printStackTrace();

}

});

}

执行结果：

waiting 1 seconds to exchange
pool-1-thread-2 got message :This is :pool-1-thread-1 do u copy?
pool-1-thread-1 got message :This is :pool-1-thread-2 copy that!

waiting 1 seconds to exchange

pool-1-thread-2 got message :This is :pool-1-thread-1 do u copy?

pool-1-thread-1 got message :This is :pool-1-thread-2 copy that!

J.U.C工具包之Exchanger

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