diff --git a/core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/stream/CollectorImprovementUnitTest.java b/core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/stream/CollectorImprovementUnitTest.java
deleted file mode 100644
index b3bef5edece8..000000000000
--- a/core-java-modules/core-java-9-improvements/src/test/java/com/baeldung/java9/language/stream/CollectorImprovementUnitTest.java
+++ /dev/null
@@ -1,61 +0,0 @@
-package com.baeldung.java9.language.stream;
-
-import org.junit.Test;
-
-import java.util.*;
-import java.util.stream.Collectors;
-import java.util.function.Function;
-
-import static org.junit.Assert.assertEquals;
-
-public class CollectorImprovementUnitTest {
-    @Test
-    public void givenList_whenSatifyPredicate_thenMapValueWithOccurences() {
-        List<Integer> numbers = List.of(1, 2, 3, 5, 5);
-
-        Map<Integer, Long> result = numbers.stream().filter(val -> val > 3).collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
-
-        assertEquals(1, result.size());
-
-        result = numbers.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.filtering(val -> val > 3, Collectors.counting())));
-
-        assertEquals(4, result.size());
-    }
-
-    @Test
-    public void givenListOfBlogs_whenAuthorName_thenMapAuthorWithComments() {
-        Blog blog1 = new Blog("1", "Nice", "Very Nice");
-        Blog blog2 = new Blog("2", "Disappointing", "Ok", "Could be better");
-        List<Blog> blogs = List.of(blog1, blog2);
-
-        Map<String, List<List<String>>> authorComments1 = blogs.stream().collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.mapping(Blog::getComments, Collectors.toList())));
-
-        assertEquals(2, authorComments1.size());
-        assertEquals(2, authorComments1.get("1").get(0).size());
-        assertEquals(3, authorComments1.get("2").get(0).size());
-
-        Map<String, List<String>> authorComments2 = blogs.stream().collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.flatMapping(blog -> blog.getComments().stream(), Collectors.toList())));
-
-        assertEquals(2, authorComments2.size());
-        assertEquals(2, authorComments2.get("1").size());
-        assertEquals(3, authorComments2.get("2").size());
-    }
-}
-
-class Blog {
-    private String authorName;
-    private List<String> comments;
-
-    public Blog(String authorName, String... comments) {
-        this.authorName = authorName;
-        this.comments = List.of(comments);
-    }
-
-    public String getAuthorName() {
-        return this.authorName;
-    }
-
-    public List<String> getComments() {
-        return this.comments;
-    }
-}
diff --git a/core-java-modules/core-java-streams-simple/src/main/java/com/baeldung/streams/collectors/Blog.java b/core-java-modules/core-java-streams-simple/src/main/java/com/baeldung/streams/collectors/Blog.java
new file mode 100644
index 000000000000..37abe5fa9913
--- /dev/null
+++ b/core-java-modules/core-java-streams-simple/src/main/java/com/baeldung/streams/collectors/Blog.java
@@ -0,0 +1,22 @@
+package com.baeldung.streams.collectors;
+
+import java.util.List;
+
+public class Blog {
+
+    private String authorName;
+    private List<String> comments;
+
+    public Blog(String authorName, String... comments) {
+        this.authorName = authorName;
+        this.comments = List.of(comments);
+    }
+
+    public String getAuthorName() {
+        return this.authorName;
+    }
+
+    public List<String> getComments() {
+        return this.comments;
+    }
+}
diff --git a/core-java-modules/core-java-streams-simple/src/test/java/com/baeldung/streams/collectors/CollectorImprovementUnitTest.java b/core-java-modules/core-java-streams-simple/src/test/java/com/baeldung/streams/collectors/CollectorImprovementUnitTest.java
new file mode 100644
index 000000000000..d650d8c6a0cd
--- /dev/null
+++ b/core-java-modules/core-java-streams-simple/src/test/java/com/baeldung/streams/collectors/CollectorImprovementUnitTest.java
@@ -0,0 +1,57 @@
+package com.baeldung.streams.collectors;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+class CollectorImprovementUnitTest {
+
+    @Test
+    void givenList_whenSatifyPredicate_thenMapValueWithOccurences() {
+        List<Integer> numbers = List.of(1, 2, 3, 5, 5);
+
+        Map<Integer, Long> result = numbers.stream()
+            .filter(val -> val > 3)
+            .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
+
+        assertEquals(1, result.size());
+
+        result = numbers.stream()
+            .collect(Collectors.groupingBy(Function.identity(), Collectors.filtering(val -> val > 3, Collectors.counting())));
+
+        assertEquals(4, result.size());
+    }
+
+    @Test
+    void givenListOfBlogs_whenAuthorName_thenMapAuthorWithComments() {
+        Blog blog1 = new Blog("1", "Nice", "Very Nice");
+        Blog blog2 = new Blog("2", "Disappointing", "Ok", "Could be better");
+        List<Blog> blogs = List.of(blog1, blog2);
+
+        Map<String, List<List<String>>> authorComments1 = blogs.stream()
+            .collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.mapping(Blog::getComments, Collectors.toList())));
+
+        assertEquals(2, authorComments1.size());
+        assertEquals(2, authorComments1.get("1")
+            .get(0)
+            .size());
+        assertEquals(3, authorComments1.get("2")
+            .get(0)
+            .size());
+
+        Map<String, List<String>> authorComments2 = blogs.stream()
+            .collect(Collectors.groupingBy(Blog::getAuthorName, Collectors.flatMapping(blog -> blog.getComments()
+                .stream(), Collectors.toList())));
+
+        assertEquals(2, authorComments2.size());
+        assertEquals(2, authorComments2.get("1")
+            .size());
+        assertEquals(3, authorComments2.get("2")
+            .size());
+    }
+}