How to interrupt a running thread in Java?


A thread can send an interrupt by invoking interrupt on the Thread object for the thread to be interrupted. This means interruption of a thread is caused by any other thread calling the interrupt() method.

The Thread class provides three interrupt methods

  • void interrupt() - Interrupts the thread.
  • static boolean interrupted() - Tests whether the current thread has been interrupted.
  • boolean isInterrupted() - Tests whether the thread has been interrupted.

Example

public class ThreadInterruptTest {
   public static void main(String[] args) {
      System.out.println("Thread main started");
      final Task task = new Task();
      final Thread thread = new Thread(task);
      thread.start();
      thread.interrupt(); // calling interrupt() method
      System.out.println("Main Thread finished");
   }
}
class Task implements Runnable {
   @Override
   public void run() {
      for (int i = 0; i < 5; i++) {
         System.out.println("[" + Thread.currentThread().getName() + "] Message " + i);
         if(Thread.interrupted()) {
            System.out.println("This thread was interruped by someone calling this Thread.interrupt()");
            System.out.println("Cancelling task running in thread " + Thread.currentThread().getName());
            System.out.println("After Thread.interrupted() call, JVM reset the interrupted value to: " + Thread.interrupted());
            break;
         }
      }
   }
}

Output

Thread main started
Main Thread finished
[Thread-0] Message 0
This thread was interruped by someone calling this Thread.interrupt()
Cancelling task running in thread Thread-0
After Thread.interrupted() call, JVM reset the interrupted value to: false
raja
Published on 10-Sep-2019 13:50:35
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