CODEWITHSUNDEEP
exceptionfinally
Matt H
Matt H

Reputation: 7389

Does try/finally ignore exceptions?

I have a situation where I want certain code to be executed no matter what happens, but I need exceptions to also be passed on up the stack to be handled later. Is the following: 


try
{
  // code
}
finally
{
  // code that must run
}

going to just ignore any exceptions, or will it pass them on up? My testing seems to show that they still get passed on up, but I want to be sure I'm not crazy.

EDIT: My question isn't about when and if the finally will execute, it's about whether exceptions still get thrown upwards, but that's been answered now.

Upvotes: 11

Views: 6253

Answers (4)

RichieHindle
RichieHindle

Reputation: 281525

The finally code will always run, and exceptions will be passed on up, as you say. That's pretty much the point of try/finally - to have some code that will always run, even when exceptions are thrown.

Edit: This is true for any language that provides the try/finally construct, but there are caveats for some languages, as Adam points out in his comment and Sam points out in his answer.

Upvotes: 18

marcc
marcc

Reputation: 12399

If this is C#:

The answers here are right, the finally is run and the exceptions are "passed up". But to illustrate how easy it is to figure it out:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static void Main(string[] args)
    {
        try
        {
            throw new Exception("testing");
        }
        finally
        {
            Console.WriteLine("Finally");
        }
    }
}

When running this simple, little console application, the exception is thrown and then the finally block is executed.

Upvotes: 2

Sam Saffron
Sam Saffron

Reputation: 131112

Assuming this is C#, finally will always run unless you get a StackOverflowException or a ExecutingEngineException

Additionally, asynchronous exceptions like ThreadAbortException can interrupt the flow of a finally block causing it to partially execute.

See related questions:

In C# will the Finally block be executed in a try, catch, finally if an unhandled exception is thrown?

Upvotes: 3

Carl Manaster
Carl Manaster

Reputation: 40336

Here's a test class that shows that (1) finally runs, regardless of whether exceptions are thrown; and (2) exceptions are passed along to the caller.

public class FinallyTest extends TestCase {
    private boolean finallyWasRun   = false;

    public void testFinallyRunsInNormalCase() throws Exception {
        assertFalse(finallyWasRun);
        f(false);
        assertTrue(finallyWasRun);
    }

    public void testFinallyRunsAndForwardsException() throws Exception {
        assertFalse(finallyWasRun);
        try {
            f(true);
            fail("expected an exception");
        } catch (Exception e) {
            assertTrue(finallyWasRun);
        }
    }

    private void f(boolean withException) throws Exception {
        try {
            if (withException)
                throw new Exception("");
        } finally {
            finallyWasRun = true;
        }
    }
}

Upvotes: 9

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