Neon Number

/*
 * Problem : Check if a number is a neon number.
 * Input   : One integer.
 * Output  : true or false.
 * Approach: Add the digits of the square.
 * Time    : O(d)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method receives a number and returns true if the number is a neon number.
    static boolean isNeon(long number) {
        // Step 1: Negative numbers are not checked.
        if (number < 0) {
            return false;
        }

        // Step 2: Calculate the square of the number. Example: 9 * 9 = 81.
        long square = number * number;

        // Step 3: Add the digits of the square. The sum starts at 0.
        long sum = 0;
        while (square > 0) {
            // Step 3a: Take the last digit and add it. Example: 81 % 10 = 1.
            sum = sum + square % 10;

            // Step 3b: Remove the last digit. Example: 81 / 10 = 8.
            square = square / 10;
        }

        // Step 4: The number is neon if the digit sum is equal to the number.
        return sum == number;
    }

    public static void main(String[] args) {
        long number = new Scanner(System.in).nextLong();
        System.out.println(isNeon(number));
    }
}