Java：如何中断/停止线程？ [英] Java: How interrupt/stop a thread?

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
}

所以，即使我调用方法'stop'，线程也不会停止。
它保持活力。

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

我如何中断/停止此线程？

How can i interrupt/stop this thread ?

更新
（@little方法）

UPDATE (@little approach)

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();
        }
    }
}

但是当我试图停止线程，它没有。
上面的代码可能有什么问题？

But when i try to stop the thread, it doesn't. What could be wrong in the code above ?

最好的问候，
Valter Henrique。

Best regards, Valter Henrique.

推荐答案

你真的没有理由需要使用 volatile 标志。相反，只需使用 isInterrupted（） 。另外，为什么要在另一个线程对象中包装 Scan 线程对象？这对我来说似乎完全没必要。

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.

这里'你应该做什么

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example 。另外，我不建议扩展 Thread 。

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

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