Postfix Evaluation

Question

I am having trouble understanding why the PostfixEvaluator method in the class PostfixEvaluator is causing a number of problems; everything else works fine.
import java.io.*;          
import javax.swing.JOptionPane;
class Stack
   private int maxSize;
   private char[] stackArray;
   private int top;
   public Stack(int s)       // Constructor of Stack
      maxSize = s;
      stackArray = new char[maxSize];
      top = -1;
   public void push(char j) {  // Puts item on top of stack
       stackArray[++top] = j; }
   public char pop(){         // Takes an item from the top of stack
   return stackArray[top--]; }
   public char peek(){        // Shows item at the top of the stack
   return stackArray[top]; }
   public boolean isEmpty(){  // Returns true if stack is empty
   return (top == -1); }
class Converter                  // This class converts Infix input to Postfix output
   private Stack theStack;
   private String input;
   private String output = "";
   public Converter(String in) { // Constructor for the Converter class
      input = in;
      int stackSize = input.length();
      theStack = new Stack(stackSize);
   public String toPostFix()    // toPostFix method
      for(int j=0; j<input.length(); j++)     
         char ch = input.charAt(j);           
         switch(ch)
            case '+':              
            case '-':
               gotOper(ch, 1);     
               break;              
            case '*':              
               gotOper(ch, 2);     
               break;              
            case '(':              
               theStack.push(ch);  
               break;
            case ')':              
               gotParen(ch);       
               break;
            default:              
               output = output + ch;
               break;
            }  // end switch
         }  // end for
      while( !theStack.isEmpty() )    
         output = output + theStack.pop();
      return output;                   // Returns Postfix Answer to User
   public void gotOper(char opThis, int prec1) // Get Operator from entered Expression
      while( !theStack.isEmpty() )
         char opTop = theStack.pop();
         if( opTop == '(' )            // if it's a '(' (left parentheses)
            theStack.push(opTop);      // Push '(' into the stack
            break;
         else                          // If it isn't a left parentheses
            int prec2;                 //
            if(opTop=='+' || opTop=='-')  // Gets precedence of operator
               prec2 = 1;     //
            else
          prec2 = 2;       // Assigns Precedence
            if(prec2 < prec1)          // Compares Precedence
               theStack.push(opTop);  
               break;
            else                      
               output = output + opTop; 
  theStack.push(opThis);
   public void gotParen(char ch)
      while( !theStack.isEmpty() )
         char chx = theStack.pop();
         if( chx == '(' )         
            break;                
         else                      
            output = output + chx; 
public class PostfixEvaluator
       StackArray stackArray = new StackArray();
       StringTokenizer tok;
       private int val1,val2;
       private int result;
    public PostfixEvaluator(String output)
    tok = new StringTokenizer(output);
     while(tok.hasMoreElements())
     String token = tok.nextToken();
     if(Numeral.isOperand(token))
     stack.push(token);
     else if(Numeral.isOperator(token))
     if(token.equals("+"))
     val1 = Integer.parseInt(stackArray.pop().toString());
     val2 = Integer.parseInt(stackArray.pop().toString());
     result = val1 + val2;
     stack.push(new Integer(result));
     else if(token.equals("-"))
     val1 = Integer.parseInt(stackArray.pop().toString());
     val2 = Integer.parseInt(stackArray.pop().toString());
     result = val2 - val1;
     stackArray.push(new Integer(result));
     else if(token.equals("*"))
     val1 = Integer.parseInt(stackArray.pop().toString());
     val2 = Integer.parseInt(stackArray.pop().toString());
     result = val1 * val2;
     stackArray.push(new Integer(result));
     else if(token.equals("/"))
     val1 = Integer.parseInt(stackArray.pop().toString());
     val2 = Integer.parseInt(stackArray.pop().toString());
     result = val2 / val1;
     stackArray.push(new Integer(result));
     public String getResult()
     return String.valueOf(stackArray.top());
class Calculator
   public static void main(String[] args) throws IOException
      String input, output;
           input = JOptionPane.showInputDialog(null, "Enter an Infix Expression:"); // Enter an infix expression
         Converter docalculation = new Converter(input); // --> See Converter Class
          output = docalculation.toPostFix(); // Does Infix to Postfix Calculation
         JOptionPane.showMessageDialog(null, "The Postfix Expression is: " + output); // Outputs the postfix expression
         JOptionPane.showMessageDialog(null, "The evaluated expression is: " + getResult(output));
   }  Edited by: babypurin on Oct 14, 2009 10:37 PM

Answer 1

I get the following compiling errors (I am having trouble interpreting what these error messages mean).
Calculator.java:123: cannot find symbolsymbol : class StackArraylocation: class Converter.PostfixEvaluator     StackArray stackArray = new StackArray();     
Calculator.java:124: cannot find symbolsymbol : class StringTokenizerlocation: class Converter.PostfixEvaluator     StringTokenizer tok;     
Calculator.java:123: cannot find symbolsymbol : class StackArraylocation: class Converter.PostfixEvaluator     StackArray stackArray = new StackArray();     Calculator.java:131: cannot find symbolsymbol : class StringTokenizerlocation: class Converter.PostfixEvaluator tok = new StringTokenizer(output);
Calculator.java:135: cannot find symbolsymbol : variable Numerallocation: class Converter.PostfixEvaluator     if(Numeral.isOperand(token))     
Calculator.java:137: cannot find symbolsymbol : variable stacklocation: class Converter.PostfixEvaluator     stack.push(token);     
Calculator.java:139: cannot find symbolsymbol : variable Numerallocation: class Converter.PostfixEvaluator     else if(Numeral.isOperator(token))     
Calculator.java:146: cannot find symbolsymbol : variable stacklocation: class Converter.PostfixEvaluator     stack.push(new Integer(result));     
Calculator.java:200: cannot find symbolsymbol : variable output2location: class Converter.Calculator     output2 = output.PostfixEvaluator(); // Calculates value of postfix expression     Calculator.java:200: cannot find symbolsymbol : method PostfixEvaluator()location: class java.lang.String     output2 = output.PostfixEvaluator(); // Calculates value of postfix expression     
Calculator.java:204: cannot find symbolsymbol : variable output2location: class Converter.Calculator JOptionPane.showMessageDialog(null, "The evaluated expression is: " + output2);
Calculator.java:188: inner classes cannot have static declarations public static void main(String[] args) throws IOException