CODEWITHSUNDEEP
javaexceptionexecutorservicecallable
HollowBastion
HollowBastion

Reputation: 223

Can't catch specific exception using ExecutorService and Callables?

The general advice for catching exceptions is that it's better to be specific, instead of just catching exceptions from the broadest class: java.lang.Exception.

But it seems like the only exception from callable is ExecutionException.

package com.company;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class ThreadTest {

    private final static ArrayList<Callable<Boolean>> mCallables = new ArrayList<>();
    private final static ExecutorService mExecutor = Executors.newFixedThreadPool(4);

    public static void main(String[] args) throws Exception{
        testMethod();
    }

    static void testMethod() throws Exception {

        mCallables.clear();

        for(int i=0; i<4; i++){
            mCallables.add(new Callable<Boolean>() {

                @Override
                public Boolean call() throws Exception {
                    //if (Thread.currentThread().isInterrupted()) {
                    //    throw new InterruptedException("Interruption");
                    //}
                    System.out.println("New call");

                    double d = Double.parseDouble("a");

                    return true;
                } //end call method

            }); //end callable anonymous class
        }
        try {
            List<Future<Boolean>> f= mExecutor.invokeAll(mCallables);
            f.get(1).get();
            f.get(2).get();
            f.get(3).get();
            f.get(0).get();

        } catch (NumberFormatException e) {
            e.printStackTrace();
            System.out.println("Number Format exception");
        } catch (ExecutionException e) {
            String s = e.toString();
            System.out.println(s);
            System.out.println("Execution exception");
        } catch (Exception e) {
            System.out.println("Some other exception");
        }

        mExecutor.shutdown();
    }
}

In the above code, I would like to catch NumberFormatException, but I can't seem to catch anything except ExecutionException.

If there are multiple different exceptions thrown from the call method, how would someone catch the different exceptions separately?

Upvotes: 1

Views: 72

Answers (1)

Mark B
Mark B

Reputation: 201088

You will always get an ExecutionException. The root exception will be set as the cause. Call getCause() on the ExecutionException instance to get to the actual exception that was thrown in the Callable.

Upvotes: 4

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