Effective Java

by Joshua Bloch

Reusing standard exceptions has several benefits. Chief among them is that it makes your API easier to learn and use because it matches the established conventions that programmers are already familiar with. A close second is that programs using your API are easier to read because they aren’t cluttered with unfamiliar exceptions. Last (and least), fewer exception classes means a smaller memory footprint and less time spent loading classes.

If a caller passes null in some parameter for which null values are prohibited, convention dictates that NullPointerException be thrown rather than IllegalArgumentException. Similarly, if a caller passes an out-of-range value in a parameter representing an index into a sequence, IndexOutOfBoundsException should be thrown rather than IllegalArgumentException.

Do not reuse Exception, RuntimeException, Throwable, or Error directly. Treat these classes as if they were abstract. You can't reliably test for these exceptions because they are superclasses of other exceptions that a method may throw.