polishNotation.java

import java.util.Scanner;
import java.util.Stack;


public class Main {
   public  static  void main(String args[]){
       Stack stack =new Stack();

       String input;

       String trimmedInput[];
       int output;
       int number1,number2;
       int countOfNumber,j;

       Scanner scanner = new Scanner(System.in);

       System.out.println("put your arithmetical expression. Using Space between ");
       input=scanner.nextLine();

       trimmedInput=input.split("\\s+");

//       for(String a:trimmedInput)
//           System.out.println(a);


       countOfNumber=trimmedInput.length;


       for(j=0;j<countOfNumber;j++) {

               if (isNumeric(trimmedInput[j])) {
                   stack.push(trimmedInput[j]);

               }
                if (trimmedInput[j].equals("+")) {
                   number1 = Integer.parseInt((String) stack.pop()) ;

                    number2 = Integer.parseInt((String) stack.pop()) ;

                   output = number1 + number2;

                   stack.push(output);

               }

               if(trimmedInput[j].equals("-")){
                   number1 = Integer.parseInt((String) stack.pop()) ;

                   number2 = Integer.parseInt((String) stack.pop()) ;

                   output = number1-number2;

                   stack.push(output);
               }
                if(trimmedInput[j].equals("*")){
                    number1 = Integer.parseInt((String) stack.pop()) ;

                    number2 = Integer.parseInt((String) stack.pop()) ;

                   output = number1*number2;

                   stack.push(output);
               }
               if(trimmedInput[j].equals("/")){
                   number1 = Integer.parseInt((String) stack.pop()) ;

                   number2 = Integer.parseInt((String) stack.pop()) ;

                   output = number1/number2;

                   stack.push(output);
               }

           }

       while(!stack.isEmpty())
           System.out.println(stack.pop());


   }
    public static boolean isNumeric(String str)
    {
        try
        {
            double d = Double.parseDouble(str);
        }
        catch(NumberFormatException nfe)
        {
            return false;
        }
        return true;
    }