Java Reference
In-Depth Information
Exceptions
Java uses exceptions as a way of signaling serious problems when you execute a program. The standard
classes use them extensively. Since they arise in your Java programs when things go wrong, and if
something can go wrong in your code, sooner or later it will, they are a very basic consideration when
you are designing and writing your programs.
The reason we've been sidestepping the question of exceptions for the past six chapters is that you first
needed to understand classes and inheritance before you could understand what an exception is, and
appreciate what happens when an exception occurs. Now that you have a good grasp of these topics we
can delve into how to use and deal with exceptions in a program.
In this chapter you will learn:
What an exception is
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How you handle exceptions in your programs
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The standard exceptions in Java
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How to guarantee that a particular block of code in a method will always be executed
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How to define and use your own types of exceptions
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How to throw exceptions in your programs
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The Idea Behind Exceptions
An exception usually signals an error, and is so-called because errors in your Java programs are bound to be
the exception rather than the rule - by definition! An exception doesn't always indicate an error though - it
can also signal some particularly unusual event in your program that deserves special attention.
