View difference between Paste ID: naUAVxS5 and btL5SgkP

 package com.company.onp;
 
 import com.company.stack.Stack;
 java.util.stack
 
 public class ONP {
     Stack stack = new Stack();
 
     public ONP(String[] args) throws OnpWrongInputException {
         for(int j=args.length-1; j>=0; j--){
             try {
                 Double num = Double.parseDouble(args[j]);
                 addDouble(num);
             }
             catch (Exception e){
                 new Addition().addToONP(this, args[j]);
                 new Subtraction().addToONP(this, args[j]);
                 new Division().addToONP(this, args[j]);
                 new Multiplication().addToONP(this, args[j]);
             }
         }
     }
 
     public Double calculate() throws OnpWrongInputException {
         Double value = 0.0;
         try {
             while(true) {
                 Double firstNumber = (Double) stack.pop();
                 Double secondNumber = (Double) stack.pop();
                 Operation operation = (Operation) stack.pop();
                 value = operation.calculate(firstNumber, secondNumber);
                 stack.push(value);
             }
         }catch (Stack.EndOfTheStackException e){
             return value;
         }catch (ClassCastException e){
             throw new OnpWrongInputException();
         }
     }
 
     protected void addOperation(Operation operation){
         stack.push(operation);
     }
 
     private void addDouble(Double number){
         stack.push(number);
     }
 
     private static class OnpWrongInputException extends Exception {
     }
 
     public static void main(String[] args) {
         try {
             ONP onp = new ONP(args);
             System.out.println(onp.stack.toString());
             System.out.println(onp.calculate());
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 
 }