How to stop a java thread gracefully?

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The good way to do it is to have the run() of the Thread guarded by a boolean variable and set it to true from the outside when you want to stop it, something like:

class MyThread extends Thread
{
  volatile boolean finished = false;

  public void stopMe()
  {
    finished = true;
  }

  public void run()
  {
    while (!finished)
    {
      //do dirty work
    }
  }
}

Once upon a time a stop() method existed but as the documentation states

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.

That’s why you should have a guard..

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