CODEWITHSUNDEEP
javamultithreading
Týna Šindelářová
Týna Šindelářová

Reputation: 177

How to stop a thread - Java

Could someone please tell me how to stop a thread if I have the following structure?

I want to stop the thread B after it expires thread C.

enter image description here

    c = new c();
    c.start();
    b = new b();
    b.start();

class c extends Thread {

    @Override
    public void run() {
      // DRAW IMAGE
      // b.stop(); - doenst work
    }
}

class b extends Thread {

    @Override
    public void run() {
      // PROGRESS BAR

    }
}

Upvotes: 1

Views: 368

Answers (9)

Aritra
Aritra

Reputation: 1224

The solution to this is explained quite well here. Any thread that might need a status flag for shutdown could have the following structure:

volatile boolean shutdownRequested;

...

public void shutdown() { shutdownRequested = true; }

public void doWork() { 
    while (!shutdownRequested) { 
        // do stuff
    }
}

Thus, in your case, your class B would look similar to the above. And then, in class C, you can call the shutdown() method of class B.

Upvotes: 1

Salah
Salah

Reputation: 8657

There is no good way to stop a thread instantly.

  • There is Thread.stop(), but it is dangerous and deprecated. Don't use it unless you have thoroughly analyzed your code and determined that the risks are acceptable.

  • There is Thread.interrupt(), but there is no guarantee that the thread will stop quickly, or even stop at all.

For Example:

while (!Thread.interrupted()) {
    try {
        //do stuff
    } catch (InterruptedException e) {
        // end up
    }
}
  • There is the approach of writing the thread to periodically check a flag, but if the flag is not checked frequently (by accident or by design), then the thread won't stop quickly.

Please Refer to this for more details

Upvotes: 5

isah
isah

Reputation: 5341

Use a Boolean flag.

For Thread safety, use AtomicBoolean.

AtomicBoolean running = new AtomicBoolean(Boolean.TRUE);

In your run() method check this flag in a while condition:

public void run(){
    while(running){
    ...
    }
}

When you want to stop this Thread, change the running to false

Upvotes: 0

Tech Nerd
Tech Nerd

Reputation: 832

Try something like

 private void startActionPerformed(java.awt.event.ActionEvent evt) {

 p=new Progress();
 myThread=new Thread(p);
 p.setLocationRelativeTo(null);
 p.setVisible(true);
 myThread.start();

}

private void stopActionPerformed(java.awt.event.ActionEvent evt) {

  if(myThread!=null){
  p.Terminate();
  try {
  myThread.join();
  } catch (InterruptedException ex) {
 Logger.getLogger(ClassA.class.getName()).log(Level.SEVERE, null, ex);
   }
   }

   }

////////////////////////////////////////////////////////////////

How it Works and Stopped!

    int i;
    volatile boolean running=true;
    public void run(){
          while(running){
      for(i=0;i<=100;i++){
    pro.setValue(i);
     try {
     Thread.sleep(200);
     } catch (InterruptedException ex) {
     Logger.getLogger(Progress.class.getName()).log(Level.SEVERE, null, ex);
    return;
    }
   if(i==100){
     Terminate();
    break;
    }
   }
 }

}

public void Terminate(){ running=false; }

/////////////////////////////////////////////////////////////////////

Upvotes: 0

Zied.Jabnoun
Zied.Jabnoun

Reputation: 140

Well, try this : 

while(true) {
  if (!c.isAlive() && b.isAlive()){
      b.interrupt();
  }
}

Upvotes: 0

s4m0k
s4m0k

Reputation: 568

Don't use Thread.stop() method, It's already deprecated, in this case you can handle the stopping of the b thread in your code.

For example:

class b extends Thread {
    private volatile boolean stopped = false;


    public void stop () {
        stopped = true;
    }

    @Override
    public void run() {
      // PROGRESS BAR
      while ( ! stopped ) {
         // paint the progress bar
      }

    }
}

Upvotes: 2

arnoschutijzer
arnoschutijzer

Reputation: 11

You might want to take a look at this. You can use a flag or just use Thread.currentThread().interrupt(), you can check if a thread is interrupted by calling Thread.isInterrupted() on it.

Upvotes: 1

Adil Shaikh
Adil Shaikh

Reputation: 44740

Don't use .stop() use interrupt() instead

You need to check periodically in your b thread if it gets interrupted, if interrupted , you can take proper actions -

if(b.isInterrupted()){
  //end your work
}

---> http://docs.oracle.com/javase/tutorial/essential/concurrency/interrupt.html

Upvotes: 2

Scary Wombat
Scary Wombat

Reputation: 44813

create a lockable object in your calling code

Boolean canRun = true;
c = new c();

when b has finished set canRun to false

periodically check value of canRun in c

Upvotes: 0

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