Java: Reads an positive integer and count the number of digits

Last update on May 14 2025 13:00:27 (UTC/GMT +8 hours)

Count Digits in an Integer

Write a Java program that reads an positive integer and count the number of digits the number (less than ten billion) has.

Test Data
Input an integer number less than ten billion: 125463

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.Scanner;
public class Exercise29 {

   public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Input an integer number less than ten billion: ");

        if (in.hasNextLong())
        {

            long n = in.nextLong();

            if (n < 0)
            {
                n *= -1;
            }
            if (n >= 10000000000L)
            {
                System.out.println("Number is greater or equals 10,000,000,000!");
            }
            else
            {
                int digits = 1;
                if (n >= 10 && n < 100)
                {
                    digits = 2;
                }
                else if (n >= 100 && n < 1000)
                {
                    digits = 3;
                }
                else if (n >= 1000 && n < 10000)
                {
                    digits = 4;
                }
                else if (n >= 10000 && n < 100000)
                {
                    digits = 5;
                }
                else if (n >= 100000 && n < 1000000)
                {
                    digits = 6;
                }
                else if (n >= 1000000 && n < 10000000)
                {
                    digits = 7;
                }
                else if (n >= 10000000 && n < 100000000)
                {
                    digits = 8;
                }
                else if (n >= 100000000 && n < 1000000000)
                {
                    digits = 9;
                }
                else if (n >= 1000000000 && n < 10000000000L)
                {
                    digits = 10;
                }
                System.out.println("Number of digits in the number: " + digits);
            }
        }
        else
        {
            System.out.println("The number is not an integer");
        }
    }
}

Sample Output:

Input an integer number less than ten billion: 125463                                                         
Number of digits in the number: 6 

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to count the digits of an integer using logarithmic functions without converting it to a string.
• Write a Java program to recursively determine the number of digits in an integer.
• Write a Java program to iteratively count the digits in an integer by repeatedly dividing by 10.
• Write a Java program to count the digits of an integer using Java 8 streams derived from its string representation.

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