Java并发：线程间数据传递和交换

Posted 2021-01-10 程序员自我修养张振力

一、通过SynchronousQueue方式实现线程间数据传递：

　　线程A与线程B共同持有一个SynchronousQueue的引用，线程B调用take方法，阻塞以等待； 线程A运行后计算出结果，将结果put到queue中;

public class SynchronousQueueTest {
    public static void main(String[] args) throws InterruptedException {

        SynchronousQueue<Integer> queue = new SynchronousQueue<Integer>();
        //线程A putThread
        Thread putThread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("put thread start");
                try {
                    Thread.sleep(3000);
                    System.out.println("put thread put对象");
                    queue.put(1);
                } catch (InterruptedException e) {
                }
                System.out.println("put thread end");
            }
        });
        //线程B takeThread
        Thread takeThread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("take thread start");
                try {
                    System.out.println("take thread 等待put对象");
                    System.out.println("take from putThread: " + queue.take());
                } catch (InterruptedException e) {
                }
                System.out.println("take thread end");
            }
        });

        putThread.start();
        takeThread.start();
    }
}

 二、线程Exchanger工具类实现线程间的数据交换：

　　当一个线程到达exchange调用点时，如果它的伙伴线程此前已经调用了此方法，那么它的伙伴会被调度唤醒并与之进行对象交换，然后各自返回。如果它的伙伴还没到达交换点，那么当前线程将会被挂起，直至伙伴线程到达——完成交换正常返回；或者当前线程被中断——抛出中断异常；又或者是等候超时——抛出超时异常。

public class ExchangerTest {

    public static void main(String[] args) {
        ExecutorService service = Executors.newCachedThreadPool();
        final Exchanger exchanger = new Exchanger();
        service.execute(new Runnable(){
            public void run() {
                try {                
                    String data1 = "thread-1-data";
                    System.out.println("线程" + Thread.currentThread().getName() +"正在把数据" + data1 +"换出去");
                    Thread.sleep((long)(Math.random()*10000));
                    String data2 = (String)exchanger.exchange(data1);
                    System.out.println("线程" + Thread.currentThread().getName() + "换回的数据为" + data2);
                }catch(Exception e){
                    
                }
            }    
        });
        service.execute(new Runnable(){
            public void run() {
                try {                
                    String data1 = "thread-2-data";
                    System.out.println("线程" + Thread.currentThread().getName() + "正在把数据" + data1 +"换出去");
                    Thread.sleep((long)(Math.random()*10000));                    
                    String data2 = (String)exchanger.exchange(data1);
                    System.out.println("线程" + Thread.currentThread().getName() + "换回的数据为" + data2);
                }catch(Exception e){
                    
                }                
            }    
        });        
    }
}