There are three ways to parse a language or a document from Java:

• with an existing library supporting specific language: for example a library to parse XML
• creating your own parser
• a tool or library to generate a parser

Use An Existing Library

You can use an existing library if you need to parse well known and supported language, like XML or HTML. A high quality library also include API for building and modifing documents in the language. This is what you can get from a basic parser. The main problem is that ther are not so much  quality libraries and the they support only the most popular languages. 

Building Your Own Custom Parser By Hand

You can choose this option if you have specific needs. If the language you need to parse cannot be parsed with traditional parser generators, or you have specific requirements that you cannot satisfy using a typical parser generator. Or maybe you need the best possible performance or a deep connection between components.

A Tool Or Library To Generate A Parser

The third option is a best one for all other situations. It is the most flexible option and has the shorter development time. Learn more what tool or library to chose to generate a parser from this tutorial.