This is a simple library for quickly adding validation code to Swing
user-interfaces. It handles validating user input when the user changes a
component's value, showing error messages and decorating components to
indicate which component is the source of the problem. It contains a large
number of built-in validators to handle most common situations, such as
validating numbers, email addresses, urls and so forth.

The primary goal is to make it easy to retrofit validation code on existing
UIs without needing to rewrite anything or add more than a few lines of code.