refactor: improving GenericRoot (#6365)

refactor: improving GenericRoot

src/main/java/com/thealgorithms/maths/GenericRoot.java

@@ -1,30 +1,48 @@
 package com.thealgorithms.maths;
 
-/*
- * Algorithm explanation:
- * https://technotip.com/6774/c-program-to-find-generic-root-of-a-number/#:~:text=Generic%20Root%3A%20of%20a%20number,get%20a%20single%2Ddigit%20output.&text=For%20Example%3A%20If%20user%20input,%2B%204%20%2B%205%20%3D%2015.
+/**
+ * Calculates the generic root (repeated digital sum) of a non-negative integer.
+ * <p>
+ * For example, the generic root of 12345 is calculated as:
+ * 1 + 2 + 3 + 4 + 5 = 15,
+ * then 1 + 5 = 6, so the generic root is 6.
+ * <p>
+ * Reference:
+ * https://technotip.com/6774/c-program-to-find-generic-root-of-a-number/
  */
 public final class GenericRoot {
+
+    private static final int BASE = 10;
+
     private GenericRoot() {
     }
 
-    private static int base = 10;
-
+    /**
+     * Computes the sum of the digits of a non-negative integer in base 10.
+     *
+     * @param n non-negative integer
+     * @return sum of digits of {@code n}
+     */
     private static int sumOfDigits(final int n) {
         assert n >= 0;
-        if (n < base) {
+        if (n < BASE) {
             return n;
         }
-        return n % base + sumOfDigits(n / base);
+        return (n % BASE) + sumOfDigits(n / BASE);
     }
 
+    /**
+     * Computes the generic root (repeated digital sum) of an integer.
+     * For negative inputs, the absolute value is used.
+     *
+     * @param n integer input
+     * @return generic root of {@code n}
+     */
     public static int genericRoot(final int n) {
-        if (n < 0) {
-            return genericRoot(-n);
+        int number = Math.abs(n);
+        if (number < BASE) {
+            return number;
         }
-        if (n > base) {
-            return genericRoot(sumOfDigits(n));
-        }
-        return n;
+        return genericRoot(sumOfDigits(number));
     }
 }