Calculator

public class Calculator {
    private int num1;
    private int num2;
    private int result;

    public Calculator(int x, int y)
    {
        num1 = x;
        num2 = y;
    }

    public int addOne(int DigitArray)
    {
        String stringNum1 = Integer.toString(DigitArray);
        String[] arrNum1 = stringNum1.split("");
        int[] newArrNum1 = new int[arrNum1.length];
           for (int i = 0; i < arrNum1.length; i++) {
              newArrNum1[i] = Integer.parseInt(arrNum1[i]);
           }
        int lastDigit = newArrNum1[newArrNum1.length-1];
        switch(lastDigit)
        {
        case 0:
            lastDigit = 1;
            System.out.println(lastDigit);
            return lastDigit;
        case 1:
            lastDigit = 2;
            System.out.println(lastDigit);
            return lastDigit;
        case 2:
            lastDigit = 3;
            System.out.println(lastDigit);
            return lastDigit;
        case 3:
            lastDigit = 4;
            System.out.println(lastDigit);
            return lastDigit;
        case 4:
            lastDigit = 5;
            System.out.println(lastDigit);
            return lastDigit;
        case 5:
            lastDigit = 6;
            System.out.println(lastDigit);
            return lastDigit;
        case 6:
            lastDigit = 7;
            System.out.println(lastDigit);
            return lastDigit;
        case 7:
            lastDigit = 8;
            System.out.println(lastDigit);
            return lastDigit;
        case 8:
            lastDigit = 9;
            System.out.println(lastDigit);
            return lastDigit;
        case 9:
            lastDigit = 0;
            updateNumberPlus(lastDigit, arrNum1, newArrNum1);
            System.out.println(lastDigit);
            return lastDigit;
        default:
            return lastDigit;
        }
    }
    public int add()
    {
        int i = 0;
        while(i <= num2)
        {
            i++;
            this.addOne(num1);
            if(i == num2)
            {
                result = 0;
                System.out.print(result);
                return result;
            }
        }
        return result;
    }

    public void updateNumberPlus(int lastDigit, String[] arrNum1, int[] newArrNum1)
    {
        int[] newNum1 = newArrNum1.clone();
        int b = newArrNum1.length;
        while(b > 0)
        {
            if(newArrNum1[b] == newNum1[b] && newNum1[b] == 0)
            {
                addOne(newNum1[b]);
            }
        }
    }
    }