[Java] Math Parser

Hi all,
This is my first try in Parser. Hope this can help you guys !
The parser_main will take the input expression and parse this one, and finally, return the value of the expression.
This is the first time I tried to code a parser. If there are bugs, please comment. I always appreciate that. ^^

I have edited this post. As I received some personal comments, I temporarily hide this code. If you have any difficulties in implementing a java parser for mathematics expression, please email me, I will help you!