Add Fibonacci series to Recursion package (#6079)

src/main/java/com/thealgorithms/Recursion/FibonacciSeries.java

@@ -0,0 +1,21 @@
+package com.thealgorithms.Recursion;
+
+/*
+    The Fibonacci series is a sequence of numbers where each number is the sum of the two preceding ones,
+    starting with 0 and 1.
+       NUMBER    0 1 2 3 4 5 6 7  8  9  10 ...
+       FIBONACCI 0 1 1 2 3 5 8 13 21 34 55 ...
+*/
+
+public final class FibonacciSeries {
+    private FibonacciSeries() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+    public static int fibonacci(int n) {
+        if (n <= 1) {
+            return n;
+        } else {
+            return fibonacci(n - 1) + fibonacci(n - 2);
+        }
+    }
+}