Gradian is a Parser Combinator library for Java. It is based on Haskell's Parsec library, and the arcsecond node.js package.
With parser combinator libraries, parsers are built up from smaller, simpler parsers. Parsers can be combined in a number of ways to produce more complex behavior. Gradian takes full advantage of this idea, providing a variety of "parser-combinators".
This library is named Gradian because of the naming of the node package it is based on, arcsecond. Both an arcsecond and a gradian are (somewhat obscure) units of angle.