Generate Java objects from String expression defined by language

Want to parse a string into java objects using some grammar like regular expression or binary operations(expressions).?????

Antlr is a good tool to use. It will generate java/c++ code easily which helps to create java objects
(http://antlr2.org/)

Below are the steps to define grammar & generate java code

Define grammar:

 Tokenization(lexer):
      Define tokens (eg. AND,OR, [a...b]*). This will be used to identify the tokens in the string given.

 Parsing(Parser):
      Define grammar/rules such that It can build the tree. Antlr will parse the given string as per the rules  and build AST tree.
 (eg. expr : expr2 (OR^ expr2)*;  pexpr :(' expr ')' -> expr;)

 TreeParser:
      Define grammar/rules to specify action at each node. These action methods can be written in java
 Now it will perform the actions specified like (construct a java object/calculate a value etc)

Generate java code :
Download the antlrworks (http://www.antlr2.org/download.html)
run the antlrworks (java -jar antlrworks-***.jar)
open the grammar files defined above and click generate

Links to sample grammar files
Lexar/Parser: https://docs.google.com/file/d/0Bzsr76b-5vDma1Jwa3dYZEZNXzg/edit
TreeParser : https://docs.google.com/file/d/0Bzsr76b-5vDmWGs4aXJoVlFqeWM/edit

This is an example of  AND/OR binary tree which can be constructed from expression

PS: This is how compilers work