Throwing generic Exception discouraged?

Question

Why is it discouraged to throw a generic (java.lang.Exception) exception, when it is usually sufficient to handle most conditional failures within a method? I understand that if a method could throw multiple types of exceptions then throwing specific subclasses of an exception might clarify the handling a bit, but in a general fail/succeed case I think Exception serves more than adequate.

Answer 1

The problem is that Exception is also the superclass of RuntimeException, which encompasses some stuff that shouldn't be caught as it indicates a problem with the programming rather than an exceptional condition that arises from context. You don't want to catch a BufferOverflowException or UnsupportedOperationException under normal circumstances. Besides, throwing separate Exception types gives the calling code control over how to handle each one. Boilerplate is reduced in Java 7 with the new multi-catch feature.

Answer 2

If you throw more specific exceptions, that does not stop any calling code from dealing with all of them in one Exception catch block. Being more specific is more documenting as to what type of errors occur, making it easier for programmers to deal with them separately.

Additionally, by throwing "Exception" itself you're basically telling callers of your code that they can't rule out any class of exception. An IOException might occur, as might a NumberFormatException, etc.