diff --git a/src/main/java/difflib/ChangeDelta.java b/src/main/java/difflib/ChangeDelta.java
index d0f4865..728decf 100644
--- a/src/main/java/difflib/ChangeDelta.java
+++ b/src/main/java/difflib/ChangeDelta.java
@@ -23,7 +23,7 @@ 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 ChangeDelta<T> extends Delta<T> {
+public final class ChangeDelta<T> extends Delta<T> {
 
     /**
      * Creates a change delta with the two given chunks.
@@ -32,7 +32,7 @@ public class ChangeDelta<T> extends Delta<T> {
      * @param revised The original chunk. Must not be {@code null}.
      */
     public ChangeDelta(Chunk<T> original, Chunk<T> revised) {
-        super(original, revised);
+        super(TYPE.CHANGE, original, revised);
     }
 
     /**
@@ -89,9 +89,4 @@ public class ChangeDelta<T> extends Delta<T> {
         return "[ChangeDelta, position: " + getOriginal().getPosition() + ", lines: "
                 + getOriginal().getLines() + " to " + getRevised().getLines() + "]";
     }
-
-    @Override
-    public TYPE getType() {
-        return Delta.TYPE.CHANGE;
-    }
 }
diff --git a/src/main/java/difflib/DeleteDelta.java b/src/main/java/difflib/DeleteDelta.java
index e3ae996..320553b 100644
--- a/src/main/java/difflib/DeleteDelta.java
+++ b/src/main/java/difflib/DeleteDelta.java
@@ -23,7 +23,7 @@ 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 DeleteDelta<T> extends Delta<T> {
+public final class DeleteDelta<T> extends Delta<T> {
 
     /**
      * Creates a change delta with the two given chunks.
@@ -32,7 +32,7 @@ public class DeleteDelta<T> extends Delta<T> {
      * @param revised The original chunk. Must not be {@code null}.
      */
     public DeleteDelta(Chunk<T> original, Chunk<T> revised) {
-        super(original, revised);
+        super(TYPE.DELETE, original, revised);
     }
 
     /**
@@ -62,11 +62,6 @@ public class DeleteDelta<T> extends Delta<T> {
         }
     }
 
-    @Override
-    public TYPE getType() {
-        return Delta.TYPE.DELETE;
-    }
-
     @Override
     public void verify(List<T> target) throws PatchFailedException {
         getOriginal().verify(target);
diff --git a/src/main/java/difflib/Delta.java b/src/main/java/difflib/Delta.java
index 62aed5f..99a6612 100644
--- a/src/main/java/difflib/Delta.java
+++ b/src/main/java/difflib/Delta.java
@@ -25,21 +25,15 @@ import java.util.*;
  */
 public abstract class Delta<T> {
 
-    /**
-     * The original chunk.
-     */
-    private Chunk<T> original;
-
-    /**
-     * The revised chunk.
-     */
-    private Chunk<T> revised;
+    private final TYPE deltaType;
+    private final Chunk<T> original;
+    private final Chunk<T> revised;
 
     /**
      * Specifies the type of the delta.
      *
      */
-    public enum TYPE {
+    public static enum TYPE {
         /**
          * A change in the original.
          */
@@ -60,13 +54,17 @@ public abstract class Delta<T> {
      * @param original Chunk describing the original text. Must not be {@code null}.
      * @param revised Chunk describing the revised text. Must not be {@code null}.
      */
-    public Delta(Chunk<T> original, Chunk<T> revised) {
+    public Delta(TYPE deltaType, Chunk<T> original, Chunk<T> revised) {
+        if (deltaType == null) {
+            throw new IllegalArgumentException("deltaType must not be null");
+        }
         if (original == null) {
             throw new IllegalArgumentException("original must not be null");
         }
         if (revised == null) {
             throw new IllegalArgumentException("revised must not be null");
         }
+        this.deltaType = deltaType;
         this.original = original;
         this.revised = revised;
     }
@@ -94,12 +92,9 @@ public abstract class Delta<T> {
      */
     public abstract void restore(List<T> target);
 
-    /**
-     * Returns the type of delta
-     *
-     * @return the type enum
-     */
-    public abstract TYPE getType();
+    public final TYPE getType() {
+        return deltaType;
+    }
 
     /**
      * @return The Chunk describing the original text.
@@ -108,13 +103,6 @@ public abstract class Delta<T> {
         return original;
     }
 
-    /**
-     * @param original The Chunk describing the original text to set.
-     */
-    public void setOriginal(Chunk<T> original) {
-        this.original = original;
-    }
-
     /**
      * @return The Chunk describing the revised text.
      */
@@ -122,13 +110,6 @@ public abstract class Delta<T> {
         return revised;
     }
 
-    /**
-     * @param revised The Chunk describing the revised text to set.
-     */
-    public void setRevised(Chunk<T> revised) {
-        this.revised = revised;
-    }
-
     @Override
     public int hashCode() {
         final int prime = 31;
diff --git a/src/main/java/difflib/InsertDelta.java b/src/main/java/difflib/InsertDelta.java
index ac2a863..a09da90 100644
--- a/src/main/java/difflib/InsertDelta.java
+++ b/src/main/java/difflib/InsertDelta.java
@@ -23,7 +23,7 @@ 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 InsertDelta<T> extends Delta<T> {
+public final class InsertDelta<T> extends Delta<T> {
 
     /**
      * Creates an insert delta with the two given chunks.
@@ -32,7 +32,7 @@ public class InsertDelta<T> extends Delta<T> {
      * @param revised The original chunk. Must not be {@code null}.
      */
     public InsertDelta(Chunk<T> original, Chunk<T> revised) {
-        super(original, revised);
+        super(TYPE.INSERT, original, revised);
     }
 
     /**
@@ -71,11 +71,6 @@ public class InsertDelta<T> extends Delta<T> {
 
     }
 
-    @Override
-    public TYPE getType() {
-        return Delta.TYPE.INSERT;
-    }
-
     @Override
     public String toString() {
         return "[InsertDelta, position: " + getOriginal().getPosition()
diff --git a/src/main/java/difflib/DiffRow.java b/src/main/java/difflib/rows/DiffRow.java
similarity index 99%
rename from src/main/java/difflib/DiffRow.java
rename to src/main/java/difflib/rows/DiffRow.java
index 08b9c26..5abb292 100644
--- a/src/main/java/difflib/DiffRow.java
+++ b/src/main/java/difflib/rows/DiffRow.java
@@ -13,7 +13,7 @@
    See the License for the specific language governing permissions and
    limitations under the License.
  */
-package difflib;
+package difflib.rows;
 
 /**
  * Describes the diff row in form [tag, oldLine, newLine) for showing the difference between two
diff --git a/src/main/java/difflib/DiffRowGenerator.java b/src/main/java/difflib/rows/DiffRowGenerator.java
similarity index 98%
rename from src/main/java/difflib/DiffRowGenerator.java
rename to src/main/java/difflib/rows/DiffRowGenerator.java
index d4abb32..d478f00 100644
--- a/src/main/java/difflib/DiffRowGenerator.java
+++ b/src/main/java/difflib/rows/DiffRowGenerator.java
@@ -13,9 +13,17 @@
    See the License for the specific language governing permissions and
    limitations under the License.
  */
-package difflib;
+package difflib.rows;
 
-import difflib.DiffRow.Tag;
+import difflib.ChangeDelta;
+import difflib.Chunk;
+import difflib.DeleteDelta;
+import difflib.Delta;
+import difflib.rows.DiffRow.Tag;
+import difflib.DiffUtils;
+import difflib.InsertDelta;
+import difflib.Patch;
+import difflib.StringUtils;
 import difflib.myers.Equalizer;
 import java.util.*;
 
diff --git a/src/test/java/diffutils/DiffRowGeneratorTest.java b/src/test/java/diffutils/rows/DiffRowGeneratorTest.java
similarity index 96%
rename from src/test/java/diffutils/DiffRowGeneratorTest.java
rename to src/test/java/diffutils/rows/DiffRowGeneratorTest.java
index 2144246..8a15d47 100644
--- a/src/test/java/diffutils/DiffRowGeneratorTest.java
+++ b/src/test/java/diffutils/rows/DiffRowGeneratorTest.java
@@ -1,7 +1,7 @@
-package diffutils;
+package diffutils.rows;
 
-import difflib.DiffRow;
-import difflib.DiffRowGenerator;
+import difflib.rows.DiffRow;
+import difflib.rows.DiffRowGenerator;
 import java.util.Arrays;
 import java.util.List;
 import static org.junit.Assert.assertEquals;