如何在Java中中断/停止线程? [英] How interrupt/stop a thread in Java?

问题描述

我正在尝试停止线程，但我不能这样做:

I'm trying to stop a thread but I can't do that :

public class Middleware {

public void read() {
    try {
        socket = new Socket("192.168.1.8", 2001);

        // code .. 

        Scan scan = new Scan();
        thread = new Thread(scan);
        thread.start();

    } catch (UnknownHostException ex) {
        ex.printStackTrace();

    } catch (IOException ex) {
        ex.printStackTrace();
    }
}

class Scan extends Thread {

    public void run() {

        while (true) {
            try {
            // my code goes here

            } catch (IOException ex) {
                thread.currentThread().interrupt();
            }
        }
    }
}

public void stop() {
    Thread.currentThread().interrupt();
}

// get and setters
}

因此，即使我调用方法"stop"，线程也不会停止. 它一直活着.

So, even when i call the method 'stop' the thread don't stop. It keeps alive.

如何中断/停止该线程?

How can I interrupt/stop this thread ?

更新 (@小方法)

private void tb_startActionPerformed(java.awt.event.ActionEvent evt) {                                         
    Middleware middleware = new Middleware();

    if (tb_start.getText().equals("Start")){
        tb_start.setText("Stop");

        // starting to read rfid tags
        middleware.read();
    }else{
        tb_start.setText("Start");

        // stop reading rfid tags
        middleware.stop();
    }
}

中间件类:

public class Middleware {

    private Scan scan;

    public void read() {

        scan = new Scan();
        scan.start();
    }

    private class Scan extends Thread {

        @Override
        public void run() {
            while (!Thread.currentThread().isInterrupted()) {
                System.out.println("reading...");
            }
        }
    }

    public void stop() {
        if (scan != null) {
            scan.interrupt();
        }
    }
}

但是当我尝试停止线程时，它没有.

But when I try to stop the thread, it doesn't.

上面的代码可能出什么问题了?

What could be wrong in the code above ?

推荐答案

实际上没有理由需要使用volatile标志.相反，只需使用 isInterrupted() .另外，为什么还要将Scan线程对象包装在另一个线程对象中?对我来说，这似乎完全没有必要.

There's really no reason you need to use a volatile flag. Instead, just query the thread for its state with isInterrupted(). Also, why are you wrapping your Scan thread object in another thread object? That seems completely unnecessary to me.

这是你应该做的

public class Middleware {
    private Scan scan;

    public void read() {
        try {
            // do stuff

            scan = new Scan();
            scan.start();
        } catch (UnknownHostException ex) {
            // handle exception
        } catch (IOException ex) {
            // handle exception
        }
    }

    private class Scan extends Thread {

        @Override
        public void run() {
            while (!Thread.currentThread().isInterrupted()) {
                try {
                    // my code goes here
                } catch (IOException ex) {
                    Thread.currentThread().interrupt();
                }
            }
        }
    }

    public void stop() {
        if(scan != null){
            scan.interrupt();
        }
    }
}

这是一个示例 .另外，我不建议扩展Thread.

Here's an example. Also, I wouldn't recommend extending Thread.

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