From dae65ce77e0153832c3608c18b1f79b5408f4954 Mon Sep 17 00:00:00 2001
From: aadislnk <adityasohanslnk@gmail.com>
Date: Thu, 18 Dec 2025 20:09:28 +0530
Subject: [PATCH] Add input validation for negative values in FibonacciSeries

---
 .../java/com/thealgorithms/recursion/FibonacciSeries.java   | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/main/java/com/thealgorithms/recursion/FibonacciSeries.java b/src/main/java/com/thealgorithms/recursion/FibonacciSeries.java
index e5f474085367..9bc6da2f7443 100644
--- a/src/main/java/com/thealgorithms/recursion/FibonacciSeries.java
+++ b/src/main/java/com/thealgorithms/recursion/FibonacciSeries.java
@@ -12,10 +12,12 @@ private FibonacciSeries() {
         throw new UnsupportedOperationException("Utility class");
     }
     public static int fibonacci(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("n must be a non-negative integer");
+        }
         if (n <= 1) {
             return n;
-        } else {
-            return fibonacci(n - 1) + fibonacci(n - 2);
         }
+        return fibonacci(n - 1) + fibonacci(n - 2);
     }
 }