String decoding

[thisum biddhika]

I'm getting inputs to my program as strings, like this:
=12+69*98
and i have to compute these values.
I tried to do this by getting the string and divide into sub strings and then to combine those with required opcodes.
(i create an ArrayList to do this)
(I took the integer values of those substrings)

but combining those strings didn't work.

As i very new to java if someone can help me, i would appriciate it.
thanks.

[Andre Uhres]

You may want to consider this parser:Parser for mathematical formulas

[Maneesh Godbole]

Nothing Swing related here.
Moving.