Question

Java. Can’t use for or while loops, thank you!

Practice by writing a recursive method that returns the number of digits in the integer passed to it as an argument of type int. Allow for both positive and negative arguments. For example, -120 has three digits. Hint: Dividing a number by 10 removes the last digit from the number

Answer 1

import java.util.Scanner;

public class NumberDigitsRecur {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.print("Enter the number : ");
        int n = scan.nextInt();         //prompt input from user
        if(n < 0)                       
            n = -n;                     //converting negative number into positive
        int noOfDigits = countDigits(n);    //function call and assigning return value to an int variable
        System.out.println("Number of digits : " + noOfDigits);
    }
    public static int countDigits(int n) {
        if(n == 0)                      //if n value is 0 then return 0
            return 0;           
        return 1 + countDigits(n / 10);     //else add 1 to each of the recursive call by dividing into 10
    }
}

OUTPUT :

Enter the number : 123456
Number of digits : 6

Enter the number : -120
Number of digits : 3