Introduction

In this demo I have used NetBeans IDE 8.2 for debugging purpose. But you can use any java programming language compiler as per your availability..

import java.util.Scanner;
public class JavaExcercise {
 
   public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter any number: ");
 
        if (in.hasNextLong())
        {
 
            long num = in.nextLong();
 
            if (num < 0)
            {
                num *= -1;
            }          
            {
                int digits = 1;
                if (num >= 10 && num < 100)
                {
                    digits = 2;
                }
                else if (num >= 100 && num < 1000)
                {
                    digits = 3;
                }
                else if (num >= 1000 && num < 10000)
                {
                    digits = 4;
                }
                else if (num >= 10000 && num < 100000)
                {
                    digits = 5;
                }
                else if (num >= 100000 && num < 1000000)
                {
                    digits = 6;
                }
                else if (num >= 1000000 && num < 10000000)
                {
                    digits = 7;
                }
                else if (num >= 10000000 && num < 100000000)
                {
                    digits = 8;
                }
                else if (num >= 100000000 && num < 1000000000)
                {
                    digits = 9;
                }
                else if (num >= 1000000000 && num < 10000000000L)
                {
                    digits = 10;
                }
                System.out.println("Number of digits in the number: " + digits);
            }
        }
        else
        {
            System.out.println("The number is not an integer");
        }
    }
}

Result