Fix: enforce utility class policy and test import rules in ReservoirSampling

Author: cureprotocols

src/main/java/com/thealgorithms/randomized/ReservoirSampling.java

@@ -14,9 +14,15 @@
  * Time Complexity: O(n)
  * Space Complexity: O(k)
  *
- * Author: Michael Alexander Montoya (@cureprotocols)
+ * @author Michael Alexander Montoya (@cureprotocols)
+ * @see <a href="https://en.wikipedia.org/wiki/Reservoir_sampling">Reservoir Sampling - Wikipedia</a>
  */
-public class ReservoirSampling {
+public final class ReservoirSampling {
+
+    // Prevent instantiation of utility class
+    private ReservoirSampling() {
+        throw new UnsupportedOperationException("Utility class");
+    }
 
     /**
      * Selects k random elements from a stream using reservoir sampling.

src/test/java/com/thealgorithms/randomized/ReservoirSamplingTest.java

@@ -1,6 +1,8 @@
 package com.thealgorithms.randomized;
 
-import static org.junit.jupiter.api.Assertions.*;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.Arrays;
 import java.util.List;
@@ -36,7 +38,7 @@ public void testSampleSizeLessThanStreamLength() {
     public void testSampleSizeGreaterThanStreamLengthThrowsException() {
         int[] stream = {1, 2, 3};
 
-        Exception exception = assertThrows(IllegalArgumentException.class, () -> { ReservoirSampling.sample(stream, 5); });
+        Exception exception = assertThrows(IllegalArgumentException.class, () -> ReservoirSampling.sample(stream, 5));
 
         assertEquals("Sample size cannot exceed stream size.", exception.getMessage());
     }