Java.lang.ThreadGroup.uncaughtException() Method


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Description

The java.lang.ThreadGroup.uncaughtException() method is called by the Java Virtual Machine when a thread in this thread group stops because of an uncaught exception, and the thread does not have a specific Thread.UncaughtExceptionHandler installed.

Declaration

Following is the declaration for java.lang.ThreadGroup.uncaughtException() method

public void uncaughtException(Thread t, Throwable e)

Parameters

  • t − This is the thread that is about to exit.

  • e − This is the uncaught exception.

Return Value

This method does not return any value.

Exception

NA

Example

The following example shows the usage of java.lang.ThreadGroup.uncaughtException() method.

package com.tutorialspoint;

import java.lang.*;

public class ThreadGroupDemo implements Runnable {

   public static void main(String[] args) {
      ThreadGroupDemo tg = new ThreadGroupDemo();
      tg.func();
   }

   public void func() {
      try {
         // create a new ThreadGroup and a child for that ThreadGroup.
         newThreadGroup pGroup = new newThreadGroup("ParentThreadGroup");
         newThreadGroup cGroup = new newThreadGroup
         (pGroup,"ChildThreadGroup");

         // create another thread
         Thread thr2 = new Thread(pGroup, this);
         System.out.println("Starting " + thr2.getName() + "...");
         // this will call run() method
         thr2.start();

         // create third thread
         Thread thr3 = new Thread(cGroup, this);
         System.out.println("Starting " + thr3.getName() + "...");
         // this will call run() method
         thr3.start();

         try {
            Thread.sleep(500);
         } catch(InterruptedException ex) {}

         // interrupt the two threads
         thr2.interrupt();
         thr3.interrupt();

         // block until the other threads finish
         thr2.join();
         thr3.join();
      } catch(InterruptedException e) {
         System.out.println(e.toString());
      }
   }

   public void run() {
      try {
         System.out.print(Thread.currentThread().getName());
         System.out.println(" executing...");

         while(true) {
            Thread.sleep(500);
         }
      } catch(InterruptedException e) {
         Thread currThread = Thread.currentThread();
         System.out.print(currThread.getName());
         System.out.println(" interrupted:" + e.toString());

         // rethrow the exception
         throw new RuntimeException(e.getMessage());
      }
   }
}

class newThreadGroup extends ThreadGroup {
    
   newThreadGroup(String n) {
      super(n);
   }
    
   newThreadGroup(ThreadGroup parent, String n) {
      super(parent, n);
   }

   public void uncaughtException(Thread t, Throwable e) {
      System.out.println(t + " has unhandled exception:" + e);
   } 
} 

Let us compile and run the above program, this will produce the following result −

Starting Thread-0...
Starting Thread-1...
Thread-0 executing...
Thread-1 executing...
Thread-0 interrupted: java.lang.InterruptedException: sleep interrupted
Thread[Thread-0,5,ParentThreadGroup] has unhandled exception: java.lang.RuntimeException: sleep interrupted
Thread-1 interrupted: java.lang.InterruptedException: sleep interrupted
Thread[Thread-1,5,ChildThreadGroup] has unhandled exception: java.lang.RuntimeException: sleep interrupted

java_lang_threadgroup.htm

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