diff --git a/core-java/src/test/java/org/baeldung/java/collections/JoinSplitCollectionsUnitTest.java b/core-java/src/test/java/org/baeldung/java/collections/JoinSplitCollectionsUnitTest.java
index d2615a4985..7efc2ab9de 100644
--- a/core-java/src/test/java/org/baeldung/java/collections/JoinSplitCollectionsUnitTest.java
+++ b/core-java/src/test/java/org/baeldung/java/collections/JoinSplitCollectionsUnitTest.java
@@ -1,31 +1,24 @@
 package org.baeldung.java.collections;
 
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
+import org.junit.Test;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import org.junit.Test;
+import static org.junit.Assert.*;
 
 public class JoinSplitCollectionsUnitTest {
 
     @Test
     public void whenJoiningTwoArrays_thenJoined() {
-        String[] animals1 = new String[] { "Dog", "Cat" };
-        String[] animals2 = new String[] { "Bird", "Cow" };
+        String[] animals1 = new String[]{"Dog", "Cat"};
+        String[] animals2 = new String[]{"Bird", "Cow"};
         String[] result = Stream.concat(Arrays.stream(animals1), Arrays.stream(animals2))
-                .toArray(String[]::new);
-    
-        assertArrayEquals(result, new String[] { "Dog", "Cat", "Bird", "Cow" });
+          .toArray(String[]::new);
+
+        assertArrayEquals(result, new String[]{"Dog", "Cat", "Bird", "Cow"});
     }
 
     @Test
@@ -33,8 +26,8 @@ public class JoinSplitCollectionsUnitTest {
         Collection<Integer> collection1 = Arrays.asList(7, 8, 9);
         Collection<Integer> collection2 = Arrays.asList(10, 11, 12);
         Collection<Integer> result = Stream.concat(collection1.stream(), collection2.stream())
-                .collect(Collectors.toList());
-    
+          .collect(Collectors.toList());
+
         assertTrue(result.equals(Arrays.asList(7, 8, 9, 10, 11, 12)));
     }
 
@@ -43,18 +36,18 @@ public class JoinSplitCollectionsUnitTest {
         Collection<Integer> collection1 = Arrays.asList(7, 8, 11);
         Collection<Integer> collection2 = Arrays.asList(9, 12, 10);
         Collection<Integer> result = Stream.concat(collection1.stream(), collection2.stream())
-                .filter(next -> next <= 10)
-                .collect(Collectors.toList());
-    
+          .filter(next -> next <= 10)
+          .collect(Collectors.toList());
+
         assertTrue(result.equals(Arrays.asList(7, 8, 9, 10)));
     }
 
     @Test
     public void whenConvertArrayToString_thenConverted() {
-        String[] colors = new String[] { "Red", "Blue", "Green", "Yellow" };
+        String[] colors = new String[]{"Red", "Blue", "Green", "Yellow"};
         String result = Arrays.stream(colors)
-                .collect(Collectors.joining(", "));
-    
+          .collect(Collectors.joining(", "));
+
         assertEquals(result, "Red, Blue, Green, Yellow");
     }
 
@@ -62,8 +55,8 @@ public class JoinSplitCollectionsUnitTest {
     public void whenConvertCollectionToString_thenConverted() {
         Collection<String> directions = Arrays.asList("Left", "Right", "Top", "Bottom");
         String result = directions.stream()
-                .collect(Collectors.joining(", "));
-    
+          .collect(Collectors.joining(", "));
+
         assertEquals(result, "Left, Right, Top, Bottom");
     }
 
@@ -73,11 +66,11 @@ public class JoinSplitCollectionsUnitTest {
         users.put(1, "John Doe");
         users.put(2, "Paul Smith");
         users.put(3, "Susan Anderson");
-    
+
         String result = users.entrySet().stream()
-                .map(entry -> entry.getKey() + " = " + entry.getValue())
-                .collect(Collectors.joining(", "));
-    
+          .map(entry -> entry.getKey() + " = " + entry.getValue())
+          .collect(Collectors.joining(", "));
+
         assertEquals(result, "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson");
     }
 
@@ -86,12 +79,12 @@ public class JoinSplitCollectionsUnitTest {
         Collection<List<String>> nested = new ArrayList<>();
         nested.add(Arrays.asList("Left", "Right", "Top", "Bottom"));
         nested.add(Arrays.asList("Red", "Blue", "Green", "Yellow"));
-    
+
         String result = nested.stream()
-                .map(nextList -> nextList.stream()
-                        .collect(Collectors.joining("-")))
-                .collect(Collectors.joining("; "));
-    
+          .map(nextList -> nextList.stream()
+            .collect(Collectors.joining("-")))
+          .collect(Collectors.joining("; "));
+
         assertEquals(result, "Left-Right-Top-Bottom; Red-Blue-Green-Yellow");
     }
 
@@ -99,9 +92,9 @@ public class JoinSplitCollectionsUnitTest {
     public void whenConvertCollectionToStringAndSkipNull_thenConverted() {
         Collection<String> fruits = Arrays.asList("Apple", "Orange", null, "Grape");
         String result = fruits.stream()
-                .filter(next -> next != null)
-                .collect(Collectors.joining(", "));
-    
+          .filter(Objects::nonNull)
+          .collect(Collectors.joining(", "));
+
         assertEquals(result, "Apple, Orange, Grape");
     }
 
@@ -112,7 +105,7 @@ public class JoinSplitCollectionsUnitTest {
         Collection<Integer> result2 = new ArrayList<>();
         AtomicInteger count = new AtomicInteger();
         int midpoint = Math.round(numbers.size() / 2);
-    
+
         numbers.forEach(next -> {
             int index = count.getAndIncrement();
             if (index < midpoint) {
@@ -121,17 +114,17 @@ public class JoinSplitCollectionsUnitTest {
                 result2.add(next);
             }
         });
-    
+
         assertTrue(result1.equals(Arrays.asList(1, 2, 3, 4, 5)));
         assertTrue(result2.equals(Arrays.asList(6, 7, 8, 9, 10)));
     }
 
     @Test
     public void whenSplitArrayByWordLength_thenConverted() {
-        String[] words = new String[] { "bye", "cold", "it", "and", "my", "word" };
+        String[] words = new String[]{"bye", "cold", "it", "and", "my", "word"};
         Map<Integer, List<String>> result = Arrays.stream(words)
-                .collect(Collectors.groupingBy(word -> word.length()));
-    
+          .collect(Collectors.groupingBy(String::length));
+
         assertTrue(result.get(2).equals(Arrays.asList("it", "my")));
         assertTrue(result.get(3).equals(Arrays.asList("bye", "and")));
         assertTrue(result.get(4).equals(Arrays.asList("cold", "word")));
@@ -141,26 +134,26 @@ public class JoinSplitCollectionsUnitTest {
     public void whenConvertStringToArray_thenConverted() {
         String colors = "Red, Blue, Green, Yellow";
         String[] result = colors.split(", ");
-    
-        assertArrayEquals(result, new String[] { "Red", "Blue", "Green", "Yellow" });
+
+        assertArrayEquals(result, new String[]{"Red", "Blue", "Green", "Yellow"});
     }
 
     @Test
     public void whenConvertStringToCollection_thenConverted() {
         String colors = "Left, Right, Top, Bottom";
         Collection<String> result = Arrays.asList(colors.split(", "));
-    
+
         assertTrue(result.equals(Arrays.asList("Left", "Right", "Top", "Bottom")));
     }
 
     @Test
     public void whenConvertStringToMap_thenConverted() {
         String users = "1 = John Doe, 2 = Paul Smith, 3 = Susan Anderson";
-    
+
         Map<Integer, String> result = Arrays.stream(users.split(", "))
-                .map(next -> next.split(" = "))
-                .collect(Collectors.toMap(entry -> Integer.parseInt(entry[0]), entry -> entry[1]));
-    
+          .map(next -> next.split(" = "))
+          .collect(Collectors.toMap(entry -> Integer.parseInt(entry[0]), entry -> entry[1]));
+
         assertEquals(result.get(1), "John Doe");
         assertEquals(result.get(2), "Paul Smith");
         assertEquals(result.get(3), "Susan Anderson");
@@ -169,12 +162,12 @@ public class JoinSplitCollectionsUnitTest {
     @Test
     public void whenConvertCollectionToStringMultipleSeparators_thenConverted() {
         String fruits = "Apple. , Orange, Grape. Lemon";
-    
+
         Collection<String> result = Arrays.stream(fruits.split("[,|.]"))
-                .map(String::trim)
-                .filter(next -> !next.isEmpty())
-                .collect(Collectors.toList());
-    
+          .map(String::trim)
+          .filter(next -> !next.isEmpty())
+          .collect(Collectors.toList());
+
         assertTrue(result.equals(Arrays.asList("Apple", "Orange", "Grape", "Lemon")));
     }
 }