Easy way of stopping Java thread gracefully

One of the easy ways of stopping thread is by use of a boolean flag. We can use a outer while loop to do our periodic task, and use combination of setStop and interrupt to end it.

Here goes the code

public class MyThread implements Runnable {
 private boolean stop;
 @Override
 public void run() {
  System.out.println("Thread starts");
  while(!stop) {
   try {
    //do something fooBar()
    System.out.println("Sleeping...");
    Thread.sleep(5000);
   } catch(InterruptedException e) {
    System.out.println("Thread was inturrupted");
   } catch(Exception e) {
    //handle error
    e.printStackTrace();
   }
   
   
  }
  System.out.println("Thread ends");
 }
 
 public void setStop(boolean stop) {
  this.stop = stop;
 }

 public static void main(String args[]) throws InterruptedException {
  MyThread m = new MyThread();
  Thread t = new Thread(m);
  t.start();
  System.out.println("Main thread Sleeping...");
  Thread.sleep(2000);
  //stop in this manner
  m.setStop(true);
  t.interrupt();
 }
}

Funny thing about Java thread

Other day, I was trying to store a thread reference which could be started whenever needed. To surprise, it threw IllegalThreadStateException. After searching I figured out that threads can be started only ones..rightly as javadoc says "It is never legal to start a thread more than once. In particular, a thread may not be restarted once it has completed execution."

So you have 3 options :
- Use thread suspend/resume
- Do not allow it to end, use Thread.sleep(time)
- Create new thread as needed