Jerry,
By now you must have understood that there is no eval function in Java as you might have used in Javascript. So you gotta right some code. Now the question is how.
The expression you have is a infix expression
Convert this expression to Postfix (lot of code available on net for this)
Evaluate this postfix expression (lot of code available on net for this too)..
Now you may implement any number of functions that your eval function will support.
I know this forum is for learning.. but if you still need others to do your homework .. we'll help

... but in the long run this will not help..