Exception Handling with Threads

Uncaught Exceptions in run method of any thread(runnable) causes thread to die off. Here is mechanism to handle these exceptions.

Java provides a way to register exception handler which is called in the case our run method has caused an exception and does not handles it. A very simple example on this is as follows :


Following is a simple handler code


package thread.exceptionHandling;

import java.lang.Thread.UncaughtExceptionHandler;

public class ExceptionHandler implements UncaughtExceptionHandler {

    @Override
    public void uncaughtException(Thread thread, Throwable exception) {
        System.out.println(thread + "  \n  " + exception);
    }
}

Here, our handler class implements UncaughtExceptionHandler, which is a static inner interface inside Thread class. detail :-  http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Thread.UncaughtExceptionHandler.html

 Following are the class implementing Runnable and the main class which make this class run.

package thread.exceptionHandling;

public class Consumer implements Runnable{

    @Override
    public void run() {
        for(int i = 0 ; i < 100 ; i++){
                System.out.println("i : " + i);
                if(i%10 == 9)
                    throw new NullPointerException("Dummy Null Pointer Exception");
                try {
                    Thread.sleep(100L);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
        }
    }

}
 


package thread.exceptionHandling;

public class MainClass {
    public static void main(String[] args) throws InterruptedException {
        Consumer consumer = new Consumer();
        Thread.setDefaultUncaughtExceptionHandler(new ExceptionHandler());
        new Thread(consumer).start();
    }
}
 
We can register the default uncaught exception for each thread too.