ArrayUtils

Author: dkropachev

core/src/main/java/com/datastax/oss/driver/internal/core/util/ArrayUtils.java

@@ -18,6 +18,7 @@
 package com.datastax.oss.driver.internal.core.util;
 
 import edu.umd.cs.findbugs.annotations.NonNull;
+import java.util.Random;
 import java.util.concurrent.ThreadLocalRandom;
 
 public class ArrayUtils {
@@ -70,14 +71,13 @@ public static <ElementT> void shuffleHead(@NonNull ElementT[] elements, int n) {
    *
    * @param elements the array to shuffle.
    * @param n the number of elements to shuffle; must be {@code <= elements.length}.
-   * @param random the {@link ThreadLocalRandom} instance to use. This is mainly intended to
-   *     facilitate tests.
+   * @param random the {@link Random} instance to use. This is mainly intended to facilitate tests.
    * @see <a
    *     href="https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm">Modern
    *     Fisher-Yates shuffle</a>
    */
   public static <ElementT> void shuffleHead(
-      @NonNull ElementT[] elements, int n, @NonNull ThreadLocalRandom random) {
+      @NonNull ElementT[] elements, int n, @NonNull Random random) {
     if (n > elements.length) {
       throw new ArrayIndexOutOfBoundsException(
           String.format(

core/src/test/java/com/datastax/oss/driver/internal/core/util/ArrayUtilsTest.java

@@ -18,11 +18,8 @@
 package com.datastax.oss.driver.internal.core.util;
 
 import static com.datastax.oss.driver.Assertions.assertThat;
-import static org.mockito.Mockito.anyInt;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
 
-import java.util.concurrent.ThreadLocalRandom;
+import java.util.Random;
 import org.junit.Test;
 
 public class ArrayUtilsTest {
@@ -86,15 +83,15 @@ public void should_not_bubble_down_when_target_index_lower() {
   @Test
   public void should_shuffle_head() {
     String[] array = {"a", "b", "c", "d", "e"};
-    ThreadLocalRandom random = mock(ThreadLocalRandom.class);
-    when(random.nextInt(anyInt()))
-        .thenAnswer(
-            (invocation) -> {
-              int i = invocation.getArgument(0);
-              // shifts elements by 1 to the right
-              return i - 2;
-            });
-    ArrayUtils.shuffleHead(array, 3, random);
+    Random deterministicRandom =
+        new Random() {
+          @Override
+          public int nextInt(int bound) {
+            // shifts elements by 1 to the right
+            return bound - 2;
+          }
+        };
+    ArrayUtils.shuffleHead(array, 3, deterministicRandom);
     assertThat(array[0]).isEqualTo("c");
     assertThat(array[1]).isEqualTo("a");
     assertThat(array[2]).isEqualTo("b");