Creating Exception Subclasses

Although Java’s built-in exceptions handle most common errors, Java’s exception handling mechanism is not limited to these errors. In fact, part of the power of Java’s approach to exceptions is its ability to handle exceptions that you create which correspond to errors in your own code. Creating an exception is easy. Just define a subclass of Exception (which is, of course, a subclass of Throwable). Your subclasses don’t need to actually implement anything—it is their existence in the type system that allows you to use them as exceptions.

The Exception class does not define any methods of its own. It does, of course, inherit those methods provided by Throwable. Thus, all exceptions, including those that you create, ...

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