#### Kaprekar Numbers

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```package com.thealgorithms.maths;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;

public final class KaprekarNumbers {
private KaprekarNumbers() {
}

/* This program demonstrates if a given number is Kaprekar Number or not.
Kaprekar Number: A Kaprekar number is an n-digit number which its square can be split into
two parts where the right part has n digits and sum of these parts is equal to the original
number. */

// Provides a list of kaprekarNumber in a range
public static List<Long> kaprekarNumberInRange(long start, long end) throws Exception {
long n = end - start;
if (n < 0) throw new Exception("Invalid range");
ArrayList<Long> list = new ArrayList<>();

for (long i = start; i <= end; i++) {
}

return list;
}

// Checks whether a given number is Kaprekar Number or not
public static boolean isKaprekarNumber(long num) {
String number = Long.toString(num);
BigInteger originalNumber = BigInteger.valueOf(num);
BigInteger numberSquared = originalNumber.multiply(originalNumber);
if (number.length() == numberSquared.toString().length()) {
return number.equals(numberSquared.toString());
} else {
BigInteger leftDigits1 = BigInteger.ZERO;
BigInteger leftDigits2;
if (numberSquared.toString().contains("0")) {
leftDigits1 = new BigInteger(numberSquared.toString().substring(0, numberSquared.toString().indexOf("0")));
}
leftDigits2 = new BigInteger(numberSquared.toString().substring(0, (numberSquared.toString().length() - number.length())));
BigInteger rightDigits = new BigInteger(numberSquared.toString().substring(numberSquared.toString().length() - number.length()));