Chapter4_Loops_Ex7

import java.util.Scanner;
/*
    =====================================================
                   chapter 4: Loops

      Ex7: Subtract & Add
    =====================================================
*/


public class MyProgram {
    public static void main(String[] args) {

        int a,b;             //user input
        int add,sub;        // add=a+b    sub=a-b
        int newNum=0;      //  creating a new number containing sub & add
        int tmp,count=0;  //   tmp for keeping numbers in tact, count= number of digits
        char sign;       //    user input for the sign + -
        Scanner s=new Scanner(System.in);

        do {
            System.out.println("Enter arithmetic Expressions: (a + b)");

            a = s.nextInt();
            sign = s.next().charAt(0);
            b = s.nextInt();

            switch (sign) {

                case '+':

                    sub = a - b;
                    add = a + b;

                    tmp = add;  //keeping number in tact

                    //loop counts the number of digits in the number
                    while (tmp > 0) {
                        tmp /= 10;
                        count++;
                    }


                    newNum = (int) (sub * Math.pow(10, count) + add);    //creating the new number
                    System.out.println(a + " + " + b + " = " + newNum); // display result
                    count = 0;  //reset counter

                    break;

                case '-':
                    System.out.println("End");
                    break;

                default:
                    System.out.println("invalid input!");
                    break;
            }
        }
            while( sign!='-' );

    }
}