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What's an Exception?

• Exceptions are "exceptional events"
• Events that are outside the normal flow of a program
• An exception is a subclass of class Exception (actually, Throwable, but more on that later)
• An exception may be "thrown" automatically, or by user code
• Can be "caught" by user code

Why Should I Care?

• Do you check for errors when you make function calls?
  • If not, you should!
  • If you do, you probably have found that the amount of code that you have to write for error checking is often more than the main flow of the code.
• Exceptions allow you to write the main flow of the code more simply, and separate out the nitty gritty details of what to do when something goes wrong.
• Exceptions also allow you to choose where to place the code to handle particular exceptions:
  • Exceptions that must be handled in the current procedure can be
  • However, some exceptions should be handled by procedures higher up the call stack.
• Exceptions allow you to clean up your code to a considerable degree
• Exceptions also force you to think about the exceptions that can occur, and have to deal with them.