Stopping the threads

Starting a thread is very easy in java, after you create it you need to call the method start(), for example:

where MyRunnable is a class implementing the Runnable interface overidden the method run().

The creation of a thread using the constructor with argument a class implementing Runnable is one of two way to create a thread, the other is to extend the class Thread, and after you call the method start() to execute the thread.

Instead, stopping the thread is much more complicated, there is a method stop() but it is deprecated.

There are two ways to stop a thread:

1. setting a flag
   consider a thread created with this Runnable:
   
   ]public class RunnableA implements Runnable { private volatile boolean running; public boolean isRunning() { return running; } public void setRunning(boolean running) { this.running = running; } @Override public void run() { running = true; while (running) { // the thread job } running = false; } }

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   ]public class RunnableA implements Runnable {       private volatile boolean running;       public boolean isRunning() { return running;     }       public void setRunning(boolean running) { this.running = running;     }       @Override     public void run() { running = true; while (running) {     // the thread job } running = false;     }   }

   
   the field “running” is used in the method run() as condition to execute the loop, setting to false the method run() returns and the thread stops.
   In order to stop a thread with this Runnable you need the line:
   
   Java

   myThread.setRunning(false);

   1	myThread.setRunning(false);

   
   Note that the field “running” is volatile so that any thread accessing to “running” gets the latest value.
2. calling the method interrupt()
   with the line:
   
   Java

   myThread.interrupt();

   1	myThread.interrupt();

   
   the thread is stopped at the first call of a method throwing the exception InterruptedException, for example wait(), join() and sleep(), as in the following:
   
   ]public class RunnableB1 implements Runnable { @Override public void run() { while (true) { // the thread job try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } }

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   ]public class RunnableB1 implements Runnable {       @Override     public void run() {   while (true) {     // the thread job     try { Thread.sleep(1000);     } catch (InterruptedException e) { e.printStackTrace();     } }       }   }

   
   If no method throwing an InterruptedException is in the code then the you have to check if the method interrupt() is called:
   
   ]public class RunnableB2 implements Runnable { @Override public void run() { while (!Thread.interrupted()) { // the thread job } } }

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   ]public class RunnableB2 implements Runnable {       @Override     public void run() {   while (!Thread.interrupted()) {     // the thread job }       }   }