diff --git a/src/main/java/difflib/patch/Chunk.java b/src/main/java/difflib/patch/Chunk.java
index c0f39c5..f2d5c61 100644
--- a/src/main/java/difflib/patch/Chunk.java
+++ b/src/main/java/difflib/patch/Chunk.java
@@ -35,7 +35,7 @@ import java.util.List;
  * @author <a href="dm.naumenko@gmail.com>Dmitry Naumenko</a>
  * @param T The type of the compared elements in the 'lines'.
  */
-public class Chunk<T> {
+public final class Chunk<T> {
 
     private final int position;
     private List<T> lines;
diff --git a/src/main/java/difflib/patch/Patch.java b/src/main/java/difflib/patch/Patch.java
index 14570ee..7732ac2 100644
--- a/src/main/java/difflib/patch/Patch.java
+++ b/src/main/java/difflib/patch/Patch.java
@@ -30,7 +30,7 @@ import java.util.ListIterator;
  * @author <a href="dm.naumenko@gmail.com">Dmitry Naumenko</a>
  * @param T The type of the compared elements in the 'lines'.
  */
-public class Patch<T> {
+public final class Patch<T> {
 
     private final List<Delta<T>> deltas = new LinkedList<>();
 
diff --git a/src/main/java/difflib/text/DiffRow.java b/src/main/java/difflib/text/DiffRow.java
index fe177fb..fe20a2c 100644
--- a/src/main/java/difflib/text/DiffRow.java
+++ b/src/main/java/difflib/text/DiffRow.java
@@ -25,7 +25,7 @@ package difflib.text;
  *
  * @author <a href="dm.naumenko@gmail.com">Dmitry Naumenko</a>
  */
-public class DiffRow {
+public final class DiffRow {
 
     private Tag tag;
     private String oldLine;
diff --git a/src/main/java/difflib/text/StringUtils.java b/src/main/java/difflib/text/StringUtils.java
index 317d700..a5dd1e7 100644
--- a/src/main/java/difflib/text/StringUtils.java
+++ b/src/main/java/difflib/text/StringUtils.java
@@ -19,7 +19,6 @@ limitations under the License.
  */
 package difflib.text;
 
-import java.util.LinkedList;
 import java.util.List;
 import static java.util.stream.Collectors.toList;