x java.util.Stack

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();
        }
    }

}