How would I Evaluate a certain formula?

Question

I have a multidimension arrayList and I ask the user for a formula and than I evaluate it. The problem is that I get user input like this:

  ((a1+a2)/12)*a3
         


        

Answer 1

A possibility is write a sort of parser. It's better to use a binary tree structure to represent an expression, rather than a list.

Each non-leaf node is an operation and every leaf is operand.