jdk中线程间的数据交换Exchanger

可以通过Exchanger类来实现线程之间的数据交换。如果一个线程执行exchange方法后若另外一个线程还没有执行到exchange方法，则当前线程会处于等待状态。

使用：

package sync;

import java.util.concurrent.Callable;
import java.util.concurrent.Exchanger;
import java.util.concurrent.FutureTask;

public class ExchangerDemo {

    public static void main(String[] args) {
        
        
        final Exchanger<String> ec = new Exchanger<>();

        Callable<String> c1 = new Callable<String>() {
            
            @Override
            public String call() throws Exception {
                System.out.println("c1 start");
                Thread.sleep(1000);
                System.out.println("c1 exchange start");
                System.out.println("c1 get:" + ec.exchange("c1 to other")); // 处于等待状态，直到另外一个线程开始交换
                System.out.println("c1 exchange end");
                return "the return of c1";
            }
        };
        
        Runnable r1 = new Runnable() {
            
            @Override
            public void run() {
                try {
                    System.out.println("r1 start");
                    Thread.sleep(5000);
                    System.out.println("r1 exchange start");
                    System.out.println("r1 get:" + ec.exchange("r1 to other"));;
                    System.out.println("r1 exchange end");
                } catch (InterruptedException e) {
                    System.out.println("r1 exchange exception");
                    e.printStackTrace();
                }
            }
        };
        
        FutureTask<String> ft = new FutureTask<>(c1);
        
        new Thread(ft).start();
        new Thread(r1).start();
        System.out.println("123");
    }

}