Java lets you create an entirely new subtype of Throwable, e.g:

public class FlyingPig extends Throwable { ... }

Now, very rarely, I may do something like this:

throw new FlyingPig("Oink!");

and of course elsewhere:

try { ... } catch (FlyingPig porky) { ... }

My questions are:

• Is this a bad idea? And if so, why?
  • What could've been done to prevent this subtyping if it is a bad idea?
  • Since it's not preventable (as far as I know), what catastrophies could result?
• If this isn't such a bad idea, why not?
  • How can you make something useful out of the fact that you can extends Throwable?