Question

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What is the best approach to handling exceptions thrown in a separate thread?

When bad things happen, my code throws an Exception, that is later being caught and handled.

If said code runs as part of a thread however, public void run() does not throw Exception. How can the executor of the tread know about exception being thrown?

Now:

 A a = new A();
 try {
    a.doSomething();
 } catch (Exception e) {
    // do something clever
 }

With Threads

 Thread t = new Thread (new A());
 t.start(); // run() calls doSomething()

If this threads fails with exception, how can i know about it?

Answer 1

You can use an ExecutorService

ExecutorService es =
Future<Type> future = ex.submit(new Callable<Type>() {
    public Type call() throws Exception {
        // do something
        return result;
    }
});

// later
try {
    Type result = future.get();
} catch(ExecutionException e) {
    Throwable exceptionThrown = e.getCause();
}

if you don’t have anything to return you can use the following.

Future<Void> future = ex.submit(new Callable<Void>() {
    public Void call() throws SpecificException {
        // do something which might throw SpecificException
        return null;
    }
});