I'm really struggling with creating a prefix notation evaluator for java. it needs to be implemented with stacks.

import java.util.Scanner;

/** * * @author kevin */ public class PreFixEvaluator { private int evaluatePrefixResult(String expression) { int result = 0; int num1, num2; String line = null; Scanner reader = new Scanner(expression); while(reader.hasNextLine()) { if(reader.) } return result; } public PreFixEvaluator() { } }