Put simply, I got tired of writing simple command line parsers for every java utility program I wrote. I wanted a simple tool that would support complex command lines - and return more than just Strings. If one of the options for a program, for example, is a number, it should be retrievable by the program AS a number. JSAP does this, and allows developers to add new command line data types as needed.

I also wanted the ability to read default values from a configuration file, which could be overridden by the command line. JSAP supports this, and in fact supports multiple, "cascading" configuration files as well.