如何给run()方法传参数

实现的方式主要有三种

1、构造函数传参

2、成员变量传参

3、回调函数传参

问题：如何实现处理线程的返回值？

1、主线程等待法（优点：实现起来简单，缺点：需要等待的变量一多的话，代码就变的非常臃肿。而且不能精准控制时间）

public class CycleWait implements Runnable{
    private String value;
    public void run() {
        try {
            Thread.currentThread().sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        value = "we have data now";
    }
 
    public static void main(String[] args) throws InterruptedException {
        CycleWait cw = new CycleWait();
        Thread t = new Thread(cw);
        t.start();
//        while (cw.value == null){
//            Thread.currentThread().sleep(100);
//        }
        t.join();
        System.out.println("value : " + cw.value);
    }
}

　　

2、使用Thread类的join()阻塞当前线程以等待子线程处理完毕（缺点：精准度不够）

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

public class MyCallable implements Callable<String> {
    @Override
    public String call() throws Exception{
        String value="test";
        System.out.println("Ready to work");
        Thread.currentThread().sleep(5000);
        System.out.println("task done");
        return  value;
    }
}

FutureTask 实现方式

public class FutureTaskDemo {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        FutureTask<String> task = new FutureTask<String>(new MyCallable());
        new Thread(task).start();
        if(!task.isDone()){
            System.out.println("task has not finished, please wait!");
        }
        System.out.println("task return: " + task.get());
    }
}

线程池实现方式

public class ThreadPoolDemo {
    public static void main(String[] args) {
        ExecutorService newCachedThreadPool = Executors.newCachedThreadPool();
        Future<String> future = newCachedThreadPool.submit(new MyCallable());
        if(!future.isDone()){
            System.out.println("task has not finished, please wait!");
        }
        try {
            System.out.println(future.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } finally {
            newCachedThreadPool.shutdown();
        }
    }
}