Stop() in threads

[sharmistha mohapatra]

Hi,

I wanted to know if stop() in jdk1.5 is deprecated,as i came across about it in the jdk1.5docs..

and is there any alternate method for the above???or its no more required ???

Regards,
Sharmistha

[Christophe Verré]

What does the API say ?

[sharmistha mohapatra]

The api says its deprecated.

stop()
Deprecated. This method is inherently unsafe. Stopping a thread with Thread.stop causes it to unlock all of the monitors that it has locked (as a natural consequence of the unchecked ThreadDeath exception propagating up the stack). If any of the objects previously protected by these monitors were in an inconsistent state, the damaged objects become visible to other threads, potentially resulting in arbitrary behavior. Many uses of stop should be replaced by code that simply modifies some variable to indicate that the target thread should stop running. The target thread should check this variable regularly, and return from its run method in an orderly fashion if the variable indicates that it is to stop running. If the target thread waits for long periods (on a condition variable, for example), the interrupt method should be used to interrupt the wait. For more information, see Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.

[sudipto shekhar]

stop() is deprecated in jdk 1.5.0. The documentation says the same.

Why is Thread.stop deprecated?
Because it is inherently unsafe. Stopping a thread causes it to unlock all the monitors that it has locked.

I don't think there is any other alternative to stop().

[Ulf Dittmer]

The way to stop a thread is have it check periodically for some boolean value that can be influenced from outside of the thread, and have the thread terminate itself (by returning) if that value ever evaluates to "true" (or "false", depending on the application logic).

[sudipto shekhar]

I produce this instead of the link so that everybody can have a look at it.

What should I use instead of Thread.stop?

Most uses of stop should be replaced by code that simply modifies some variable to indicate that the target thread should stop running. The target thread should check this variable regularly, and return from its run method in an orderly fashion if the variable indicates that it is to stop running. (This is the approach that JavaSoft's Tutorial has always recommended.) To ensure prompt communication of the stop-request, the variable must be volatile (or access to the variable must be synchronized).

For example, suppose your applet contains the following start, stop and run methods:

 
    private Thread blinker;

    public void start() {
        blinker = new Thread(this);
        blinker.start();
    }

    public void stop() {
        blinker.stop();  // UNSAFE!
    }

    public void run() {
        Thread thisThread = Thread.currentThread();
        while (true) {
            try {
                thisThread.sleep(interval);
            } catch (InterruptedException e){
            }
            repaint();
        }
    }


   

You can avoid the use of Thread.stop by replacing the applet's stop and run methods with:

  
 private volatile Thread blinker;

    public void stop() {
        blinker = null;
    }

    public void run() {
        Thread thisThread = Thread.currentThread();
        while (blinker == thisThread) {
            try {
                thisThread.sleep(interval);
            } catch (InterruptedException e){
            }
            repaint();
        }
    }

  

Hope this helps

[sudipto shekhar]

Thanks Ulf