Collecting Exceptions from Threads in ThreadPoolExecutor

Question

Hi,
I have a scenario where I am using a thread pool executor to submit threads. and then, I am waiting at the end for all threads to finish using below code.
threadPoolExecutor.shutdown();
try {
while (!threadPoolExecutor.awaitTermination(1000L, TimeUnit.MILLISECONDS)) {
// awaiting termination of all the threads here.
What I required is, I want to catch the exceptions that are been thrown by one of the threads in ThreadPoolExecutor in my method where I am submitting threads and want to do some processing based on those exceptions.
Is it possible to catch those exceptions that are been thrown by the threads in ThreadPoolExecutor? If so, can some one please let me know how to do that?
Thanks
Pallavi
Here is sample code:
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class sample2 { 
ThreadPoolExecutor threadPoolExecutor = null;
public sample2()
super();
threadPoolExecutor = new ThreadPoolExecutor(5,10,5,TimeUnit.MINUTES, new ArrayBlockingQueue(10));
public static void main(String[] args) throws IOException
sample2 s = new sample2();
s.checkThreadPoolExecutor();
System.out.println("I am done with calling all threads- waiting for threads to finish");
s.threadPoolExecutor.shutdown();
try {
while (!s.threadPoolExecutor.awaitTermination(1000L, TimeUnit.MILLISECONDS)) {
// awaiting termination of all the threads here.
catch(Exception e)
System.out.println("Exception while waiting fot threads to finish");
s.threadPoolExecutor.shutdown();
System.out.println("Bye bye");
public class TestThread implements Callable<Integer>
int i =0;
String sample = null;
public TestThread(int i)
this.i = i;
@Override
public Integer call() {
System.out.println("I am thread-"+i + "and sleeping for 1 min");
try
Thread.sleep(1000*5);
catch(InterruptedException ie)
System.out.println("some one woke me up");
try{
String test = sample.substring(0,1);
catch(Exception e)
throw new RuntimeException(e);
return i;
private void checkThreadPoolExecutor()
for(int i = 0; i <10;i++)
testMethod(i);
System.out.println("I am done with i:" + i + " in checkThreadPoolExec");
private void testMethod(int i)
TestThread thread = new TestThread(i);
Future<Integer> future = threadPoolExecutor.submit(thread);
Edited by: Pallavi.Palleti on Feb 17, 2009 7:41 PM

Answer 1

Hi,
some hints for future postings:
- use code-tags when submitting code (tags are available at icon bar at the top of your message editor); this will make your code easier to read given you preserved proper indentation when copying it to your posting
- class names should start with an upper case letter (e.g. "public class Sample2" instead of "public class sample")
- you do not submit "Threads" to an executor, you either submit Runnables or Callables; Threads are pooled inside the executor to execute the Runnables/Callables you submit
As for your question: where exactly do you want to handle the exception? Within your Runnable or when checking the result of the Future? For the second case, Future.get() should throw an ExecutionException if the underlying Runnable/Callable threw an exception.
In general, there is the concept of an UncaughtExceptionHandler that will take care of any execptions that occur and have not been handled by the corresponding implementation.
Bye.