refactor: improving Median (#6404)

refactor: improving Median

Co-authored-by: Deniz Altunkapan <93663085+DenizAltunkapan@users.noreply.github.com>

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

@@ -13,8 +13,13 @@ public final class Median {
      * Calculate average median
      * @param values sorted numbers to find median of
      * @return median of given {@code values}
+     * @throws IllegalArgumentException If the input array is empty or null.
      */
     public static double median(int[] values) {
+        if (values == null || values.length == 0) {
+            throw new IllegalArgumentException("Values array cannot be empty or null");
+        }
+
         Arrays.sort(values);
         int length = values.length;
         return length % 2 == 0 ? (values[length / 2] + values[length / 2 - 1]) / 2.0 : values[length / 2];

src/test/java/com/thealgorithms/maths/MedianTest.java

@@ -1,6 +1,7 @@
 package com.thealgorithms.maths;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
@@ -34,4 +35,10 @@ public class MedianTest {
         int[] arr = {-27, -16, -7, -4, -2, -1};
         assertEquals(-5.5, Median.median(arr));
     }
+
+    @Test
+    void medianEmptyArrayThrows() {
+        int[] arr = {};
+        assertThrows(IllegalArgumentException.class, () -> Median.median(arr));
+    }
 }