algorithms 2nd year coursework

very basic question, anyone who has any programing experience should be able to complete this in about 15 mins r probably less!! ## Deliverables **Modify the PostFixEvaluator program to use a ListStack and then evaluate the expression:** ** 3 4 * 2 5 + - 4 * 2 /** ** Explain in words the behaviour of the program.** Shown below is the code that i was provided with in order to start the question //******************************************************************** // [login to view URL] Authors: Lewis/Chase // // Represents an evaluator of postfix expressions. Assumes the // operands are constants. //********************************************************************import [login to view URL]; import [login to view URL];public class PostfixEvaluator { private final char ADD = '+', SUBTRACT = '-'; private final char MULTIPLY = '*', DIVIDE = '/'; private ArrayStack stack; //----------------------------------------------------------------- // Sets up this evalutor by creating a new stack. //----------------------------------------------------------------- public PostfixEvaluator() { stack = new ArrayStack(); } //----------------------------------------------------------------- // Evaluates the specified postfix expression. //----------------------------------------------------------------- public int evaluate (String expr) { int op1, op2, result = 0; String token; StringTokenizer tokenizer = new StringTokenizer (expr); while ([login to view URL]()) { token = [login to view URL](); if (isOperator(token)) { op2 = ((Integer)[login to view URL]()).intValue(); op1 = ((Integer)[login to view URL]()).intValue(); result = evalSingleOp ([login to view URL](0), op1, op2); [login to view URL] (new Integer(result)); } else [login to view URL] (new Integer([login to view URL](token))); } return result; } // Determines if the specified token is an operator. private boolean isOperator (String token) { return ( [login to view URL]("+") || [login to view URL]("-") || [login to view URL]("*") || [login to view URL]("/") ); } // Evaluates a single expression consisting of the specified // operator and operands. private int evalSingleOp (char operation, int op1, int op2) { int result = 0; switch (operation) { case ADD: result = op1 + op2; break; case SUBTRACT: result = op1 - op2; break; case MULTIPLY: result = op1 * op2; break; case DIVIDE: result = op1 / op2; } return result; } } ## Platform not entirely sure but i would think that it would in most versions of windows. the program itself has to run on a program called "J Creator"