🔢 Today I Learned: Counting Digits in Java

Today I learned how to count how many times a particular digit appears in a number using Java ☕

💻 The Code

import java.util.Scanner;

public class DigitCount {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter a number: ");
        int N = sc.nextInt();

        System.out.println("Enter a digit to count: ");
        int D = sc.nextInt();

        int count = 0;

        while (N > 0) {
            int lastDigit = N % 10; // extract last digit
            if (lastDigit == D) {
                count++;
            }
            N = N / 10; // remove last digit
        }

        System.out.println("Digit " + D + " appears " + count + " times.");
        sc.close();
    }
}

🔎 How It Works

• Take input N (the number) and D (the digit to count).
• Initialize count = 0.
• Loop while N > 0:
• Extract the last digit using % 10.
• Compare it with D. If equal → increment count.
• Remove the last digit using / 10.
• Print the final count.

This is a very simple and logical approach to digit problems, and it feels quite mathematical.
I loved solving it 💡

🚀 Alternative Approaches

There are many ways to solve this same problem:

1. String Conversion

Convert the number to a string → loop over characters → compare with the digit.

String str = String.valueOf(N);
long count = str.chars().filter(ch -> ch == (D + '0')).count();

This approach uses Java Streams.

1. Recursion

You can solve it with recursion by checking the last digit and then calling the method with N / 10.

1. Arrays / Collections

Extract digits into an array/list and count with a loop or streams.

❓ Discussion

Which method do you prefer for solving such problems?
➡️ Math-based loops (% and /)
➡️ String-based tricks

🏷️ Suggested Tags

java #beginners #tutorial #problem-solving