Evaluating Infix Expressions Using Generic Stacks

I am given the task to create a program that evaluates infix expressions using two generic stacks, one operator stack and one value stack.

This is my GenStack.java file:

import java.util.*;
public class GenStack<T>{//T is the type parameter
private Node top;//top of stack
public class Node {//defines each node of stack
T value;
Node next;

[Code] ....

I'm having trouble with the eval and apply methods. The eval method doesn't appear to pickup ')' characters, like it doesn't even see them.