Why throw RuntimeException Error instead of IOException Message?

Question

I get this piece of code from a game book. The author explains that it will open a music file

public Music newMusic(String filename) {
    try {
        AssetFileDescriptor assetDescriptor = assets.openFd(filename);
        return new AndroidMusic(assetDescriptor);
    } catch (IOException e) {
        throw new RuntimeException("Couldn't load music '" + filename + "'");
    }
}

The method AssetFileDescriptor.openFd(filename) throws a IOException.

My question is: why do we need throw a RuntimeException message instead of IOException message?

The main downside I can see is that since IOException is a checked exception, and since the method isn't handling it, the method header will have to have throws IOException. — saiarcot895
– saiarcot895, Commented Feb 24, 2014 at 22:54
The reason pointed was the use of IOException would clutter "the calling code considerably". I didn't understand that — Hellon Canella Machado
– Hellon Canella Machado, Commented Feb 24, 2014 at 23:01

Warren Dew · Accepted Answer · 2014-02-24 23:04:10Z

4

An IOException is a checked exception and must be declared by any method that throws it. A RuntimeException is unchecked and can be thown from any method.

Wrapping a checked exception in a RuntimeException, as in the example code, is normally done when the checked exception cannot be recovered from locally and it's considered acceptable for the exception to result in the program's failure. Once the checked exception is wrapped in the RuntimeException, the RuntimeException can then propagate all the way up the stack, if it occurs, regardless of the presence or absence of exception declarations.

edited Feb 24, 2014 at 23:04

answered Feb 24, 2014 at 22:56

Warren Dew

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1 Comment

Dave Newton Over a year ago

It goes quite a bit beyond recoverability, though.

Dave Newton · Accepted Answer · 2014-02-24 22:54:14Z

1

So you don't need to declare the calling methods as catching or throwing IOException.

Checked exceptions may be nice in some situations, but not everywhere.

answered Feb 24, 2014 at 22:54

Dave Newton

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4 Comments

Trein Over a year ago

Probably it's also interesting to explain what the difference between Checked and Unchecked exception.

Hellon Canella Machado Over a year ago

I know that. But author explain that even using a try-catch for a IOException is better rethrow that as RuntimeException. The reason pointed was the use of IOException would clutter "the calling code considerably". I didn't understand that.

Dave Newton Over a year ago

@HellonCanellaMachado Declaring exceptions to be thrown and caught all over is noisy; it detracts from what the code is trying to actually do. Note that most other languages don't even have checked exceptions; some take that as evidence it was an experiment that failed. There are a lot of circumstances where the syntactic overhead of checked exceptions isn't worth it.

Hellon Canella Machado Over a year ago

Thanks dude. I'll think of it.

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