polish stack

Hello,
I am looking for a Java source code for Polish Stack, please.
A Polish Stack - A Stack algoritm, that is usefull for developing a tool
for 
computing basic formulas, with priority.
i.e a formula :
2 + 3 x 5 = 17 (and not 25, because x is perior to +)
The function that evaluate this can be done by some recrusive statements 
(which I don't preffer), or by polish-stack.

If there is no source code :
What is the concept of polish stack ?

Thanks :)