如何实现处理线程的返回值

方法有以下几种：

主线程等待法

使用Thread类的join()阻塞当前线程以等待子线程处理完毕

通过Callable接口实现： 通过FutureTask Or线程池获取

 

一、主线程等待法

如下代码

public class CycleWait implements  Runnable {

    private String name;

    @Override
    public void run() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        name = "zhang san";
    }

    public static void main(String[] args) {
        CycleWait cw = new CycleWait();
        Thread t = new Thread(cw);
        t.start();
        System.out.println("name: " + cw.name);
    }
}

　　打印的结果为

 

 

将它改造成主线程等待法

public class CycleWait implements  Runnable {

    private String name;

    @Override
    public void run() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        name = "zhang san";
    }

    public static void main(String[] args) throws InterruptedException {
        CycleWait cw = new CycleWait();
        Thread t = new Thread(cw);
        t.start();
        while (cw.name == null){
            Thread.sleep(100);
        }
        System.out.println("name: " + cw.name);
    }
}

　　这样，5秒后就能打印name的值

 

二、使用Thread类的join()阻塞当前线程以等待子线程处理完毕

修改上上面的方法

 

 

三、通过Callable接口实现： 通过FutureTask Or线程池获取

1、通过FutureTask 

创建MyCallback 类，实现Callable接口

public class MyCallback implements Callable<String>{

    @Override
    public String call() throws Exception {
        String value = "nick";
        System.out.println("Read to work");
        Thread.sleep(5000);
        System.out.println("task done");
        return value;
    }
}

　　使用FutureTask的方式

public class FutureTaskDemo {

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        FutureTask<String> task = new FutureTask<String>(new MyCallback());
        new Thread(task).start();

        if(!task.isDone()){
            System.out.println("任务没有完成，请等待");
        }
        System.out.println("任务返回：" + task.get());

    }

}

　　打印结果

任务没有完成，请等待
Read to work
task done
任务返回：nick

　　

2、使用线程池的方式

public class SomeCallable {

    public static void main(String[] args)  {
        Callable<String> callbale = new Callable<String>() {
            @Override
            public String call() throws Exception {
                Thread.sleep(2000);
                return "ok";
            }
        };

        ExecutorService executorService = Executors.newFixedThreadPool(2);
        //执行任务并获取Future对象
        Future<String> future = executorService.submit(callbale);

        try {
            String result =  future.get();
            System.out.println("result:" + result);
        }catch (Exception e){}
        finally {
            //关闭线程池
            executorService.shutdown();
        }
      
      


    }
}