SCJP Question: Handle Exceptions

Question

Hi, I'm studying for Java Programmer Certification (SCJP) exam. A question about exceptions, when handle exceptions is it best to handle a specific exception like NumberFormatException or catch all exceptions use the parent Exception class?

Base on my course unchecked exceptions are basically a RunTimeException which mostly result of a program bug. Does this mean that when I throw an exception manually I should rather use:

new Exception("... my message...")

and that I shouldn't handle RunTimeException? Only handle checked exceptions?

Answer 1

You should handle as specific Exceptions as possible. If you know when a RuntimeException may be thrown, you should usually fix your program so it doesn't throw that Exception.

As far as catching checked Exceptions go, you should handle as specific an Exception as you can so:

try {
} catch (FileNotFoundException fnfe){
} catch (IOException ioe){
} catch (Exception e){
}

When you are throwing Exceptions, you should almost never use throw new Exception(). Throw an exception that can give someone who sees it some more information about what happened when it was thrown. (i.e. IndexOutOfBounds or NullPointerExceptions. They give specific info w/out even looking at the message or stacktrace.)

If you want to throw an Exception, and you don't think the Java API has one that fits your case, it is best to subclass or extend the Exception giving it a very informative name.

Answer 2

You can subclass Exception (instead of RuntimeException) in those cases.

Answer 3

Also look into exception chaining