solves #3099: Harshad Number in java

Author: anishLearnsToCode

Diff for: README.md

@@ -901,7 +901,7 @@
 | 3083 | [Existence of a Substring in a String and Its Reverse](https://leetcode.com/problems/existence-of-a-substring-in-a-string-and-its-reverse)                             |                                                                         [![Java](assets/java.png)](src/ExistenceOfASubstringInAStringAndItsReverse.java)                                                                         |                                                                                                                                   |
 | 3090 | [Maximum Length Substring With Two Occurrences](https://leetcode.com/problems/maximum-length-substring-with-two-occurrences)                                           |                                                                          [![Java](assets/java.png)](src/MaximumLengthSubstringWithTwoOccurrences.java)                                                                           |                                                                                                                                   |
 | 3095 | [Shortest Subarray With OR at Least K I](https://leetcode.com/problems/shortest-subarray-with-or-at-least-k-i)                                                         |                                                                               [![Java](assets/java.png)](src/ShortestSubarrayWithORAtLeastKI.java)                                                                               |                                                                                                                                   |
-| 3099 | [Harshad Number](https://leetcode.com/problems/harshad-number)                                                                                                         |                                                                                                                                                                                                                                  |                                                                                                                                   |
+| 3099 | [Harshad Number](https://leetcode.com/problems/harshad-number)                                                                                                         |                                                                                        [![Java](assets/java.png)](src/HarshadNumber.java)                                                                                        |                                                                                                                                   |
 | 3105 | [Longest Strictly Increasing or Strictly Decreasing Subarray](https://leetcode.com/problems/longest-strictly-increasing-or-strictly-decreasing-subarray)               |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3110 | [Score of a String](https://leetcode.com/problems/score-of-a-string)                                                                                                   |                                                                                                                                                                                                                                  |                                                                                                                                   |
 | 3114 | [Latest Time You Can Obtain After Replacing Characters](https://leetcode.com/problems/latest-time-you-can-obtain-after-replacing-characters)                           |                                                                                                                                                                                                                                  |                                                                                                                                   |

Diff for: src/HarshadNumber.java

@@ -0,0 +1,22 @@
+// https://leetcode.com/problems/harshad-number
+// T: O(log(N))
+// S: O(1)
+
+public class HarshadNumber {
+    public int sumOfTheDigitsOfHarshadNumber(int x) {
+        final int sumOfDigits = sumOfDigits(x);
+        if (x % sumOfDigits == 0) {
+            return sumOfDigits;
+        }
+        return -1;
+    }
+
+    private static int sumOfDigits(int x) {
+        int sum = 0;
+        while (x > 0) {
+            sum += x % 10;
+            x /= 10;
+        }
+        return sum;
+    }
+}