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Thread: Reverse Polish Notation Calculator

  1. #1
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    Default Reverse Polish Notation Calculator

    Here is my code for what i have done using an array stack.
    there are no errors but my program doesn't return the final value when I enter "="
    import cs2.*;
    import java.util.Scanner;
     
    public class ArrayStack<T> implements Stack<T>
      {
     
        private T[] data;
     
        private int topIndex;
     
        @SuppressWarnings("unchecked")
        public ArrayStack (int initSize)
          { data = (T[])new Object[initSize];
            topIndex = -1;
          } // Constructor
     
        public ArrayStack ()
          { this(100);
          } // Constructor
     
          public void push (T item)
     
    // Push the new item onto an ArrayStack
    { if (topIndex >= data.length-1)
    throw new NoSpaceAvailableException();
    data[++topIndex] = item;
    } // push
     
     
    public T pop () // Pop item off top of stack
    { if (topIndex < 0)
    throw new EmptyException("stack is empty");
    return data[topIndex--];
    } // pop
     
    public T top () // Return a copy of top item
    { if (topIndex < 0)
    throw new EmptyException("stack is empty");
    return data[topIndex];
    } // top
     
     
    public boolean isEmpty ()
    // Return TRUE if no items on stack
    { return topIndex < 0;
    } // isEmpty
     
    //public static double execute(String expr)
     
     
     
     
          	public static void main(String[] args)
          	{
    ArrayStack<Double> st = new ArrayStack<>();
     
     
    Scanner scan = new Scanner(System.in);
     
     
    Object x = scan.next();
     
     
     
     
            while(scan.hasNext())
            {
                if(scan.hasNextDouble())
                {
                        st.push(scan.nextDouble());
                }
                else
                {
     
                    double a, b;
     
     
     
                            if (x == '+')
                            {a = st.pop();
                            b = st.pop();
                            st.push(b + a);}
     
                            else if (x == '-')
                            {a = st.pop();
                            b = st.pop();
                            st.push(b - a);}
                            else if (x == '*')
                            {a = st.pop();
                            b = st.pop();
                            st.push(b * a);}
     
     
     
                            else if (x == '/')
                            {a = st.pop();
                            b = st.pop();
                            st.push(b / a);}
     
     
                            else if (x == '=')
                            {st.pop();
                            System.out.print("The answer is" + st.pop());
     
                            }
     
                        }
                   }
     
     
     
     
     
          	} //main
     
      }// class ArrayStack
    Last edited by helloworld922; May 9th, 2012 at 12:56 AM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Reverse Polish Notation Calculator

    what does it return? Post the print out from the program.

    Please Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting
    If you don't understand my answer, don't ignore it, ask a question.

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