diff --git a/java-diff-utils-jgit/src/main/java/com/github/difflib/algorithm/jgit/HistogramDiff.java b/java-diff-utils-jgit/src/main/java/com/github/difflib/algorithm/jgit/HistogramDiff.java
index 0476b26..a171505 100644
--- a/java-diff-utils-jgit/src/main/java/com/github/difflib/algorithm/jgit/HistogramDiff.java
+++ b/java-diff-utils-jgit/src/main/java/com/github/difflib/algorithm/jgit/HistogramDiff.java
@@ -36,7 +36,8 @@
 public class HistogramDiff<T> implements DiffAlgorithmI<T> {
 
 		@Override
-		public List<Change> computeDiff(List<T> source, List<T> target, DiffAlgorithmListener progress) {
+		public List<Change> computeDiff(
+						List<? extends T> source, List<? extends T> target, DiffAlgorithmListener progress) {
 				Objects.requireNonNull(source, "source list must not be null");
 				Objects.requireNonNull(target, "target list must not be null");
 				if (progress != null) {
@@ -92,9 +93,9 @@ public int hash(DataList<T> s, int i) {
 
 class DataList<T> extends Sequence {
 
-		final List<T> data;
+		final List<? extends T> data;
 
-		public DataList(List<T> data) {
+		public DataList(List<? extends T> data) {
 				this.data = data;
 		}
 
diff --git a/java-diff-utils/src/main/java/com/github/difflib/DiffUtils.java b/java-diff-utils/src/main/java/com/github/difflib/DiffUtils.java
index e43be50..8448a76 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/DiffUtils.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/DiffUtils.java
@@ -57,7 +57,8 @@ public static void withDefaultDiffAlgorithmFactory(DiffAlgorithmFactory factory)
 		 * @param progress a {@link DiffAlgorithmListener} representing the progress listener. Can be {@code null}.
 		 * @return The patch describing the difference between the original and revised sequences. Never {@code null}.
 		 */
-		public static <T> Patch<T> diff(List<T> original, List<T> revised, DiffAlgorithmListener progress) {
+		public static <T> Patch<T> diff(
+						List<? extends T> original, List<? extends T> revised, DiffAlgorithmListener progress) {
 				return DiffUtils.diff(original, revised, DEFAULT_DIFF.create(), progress);
 		}
 
@@ -69,7 +70,7 @@ public static <T> Patch<T> diff(List<T> original, List<T> revised, DiffAlgorithm
 		 * @param revised a {@link List} representing the revised sequence of elements. Must not be {@code null}.
 		 * @return The patch describing the difference between the original and revised sequences. Never {@code null}.
 		 */
-		public static <T> Patch<T> diff(List<T> original, List<T> revised) {
+		public static <T> Patch<T> diff(List<? extends T> original, List<? extends T> revised) {
 				return DiffUtils.diff(original, revised, DEFAULT_DIFF.create(), null);
 		}
 
@@ -82,7 +83,7 @@ public static <T> Patch<T> diff(List<T> original, List<T> revised) {
 		 * @param includeEqualParts a {@link boolean} representing whether to include equal parts in the resulting patch.
 		 * @return The patch describing the difference between the original and revised sequences. Never {@code null}.
 		 */
-		public static <T> Patch<T> diff(List<T> original, List<T> revised, boolean includeEqualParts) {
+		public static <T> Patch<T> diff(List<? extends T> original, List<? extends T> revised, boolean includeEqualParts) {
 				return DiffUtils.diff(original, revised, DEFAULT_DIFF.create(), null, includeEqualParts);
 		}
 
@@ -110,7 +111,8 @@ public static Patch<String> diff(String sourceText, String targetText, DiffAlgor
 		 * @return The patch describing the difference between the original and
 		 * revised sequences. Never {@code null}.
 		 */
-		public static <T> Patch<T> diff(List<T> source, List<T> target, BiPredicate<T, T> equalizer) {
+		public static <T> Patch<T> diff(
+						List<? extends T> source, List<? extends T> target, BiPredicate<? super T, ? super T> equalizer) {
 				if (equalizer != null) {
 						return DiffUtils.diff(source, target, DEFAULT_DIFF.create(equalizer));
 				}
@@ -118,7 +120,10 @@ public static <T> Patch<T> diff(List<T> source, List<T> target, BiPredicate<T, T
 		}
 
 		public static <T> Patch<T> diff(
-						List<T> original, List<T> revised, DiffAlgorithmI<T> algorithm, DiffAlgorithmListener progress) {
+						List<? extends T> original,
+						List<? extends T> revised,
+						DiffAlgorithmI<T> algorithm,
+						DiffAlgorithmListener progress) {
 				return diff(original, revised, algorithm, progress, false);
 		}
 
@@ -135,8 +140,8 @@ public static <T> Patch<T> diff(
 		 * revised sequences. Never {@code null}.
 		 */
 		public static <T> Patch<T> diff(
-						List<T> original,
-						List<T> revised,
+						List<? extends T> original,
+						List<? extends T> revised,
 						DiffAlgorithmI<T> algorithm,
 						DiffAlgorithmListener progress,
 						boolean includeEqualParts) {
@@ -157,7 +162,8 @@ public static <T> Patch<T> diff(
 		 * @return The patch describing the difference between the original and
 		 * revised sequences. Never {@code null}.
 		 */
-		public static <T> Patch<T> diff(List<T> original, List<T> revised, DiffAlgorithmI<T> algorithm) {
+		public static <T> Patch<T> diff(
+						List<? extends T> original, List<? extends T> revised, DiffAlgorithmI<T> algorithm) {
 				return diff(original, revised, algorithm, null);
 		}
 
@@ -196,7 +202,7 @@ public static Patch<String> diffInline(String original, String revised) {
 		 * @return the revised list.
 		 * @throws PatchFailedException if the patch cannot be applied.
 		 */
-		public static <T> List<T> patch(List<T> original, Patch<T> patch) throws PatchFailedException {
+		public static <T> List<T> patch(List<? extends T> original, Patch<T> patch) throws PatchFailedException {
 				return patch.applyTo(original);
 		}
 
@@ -208,7 +214,7 @@ public static <T> List<T> patch(List<T> original, Patch<T> patch) throws PatchFa
 		 * @return the original list.
 		 * @throws PatchFailedException if the patch cannot be applied.
 		 */
-		public static <T> List<T> unpatch(List<T> revised, Patch<T> patch) {
+		public static <T> List<T> unpatch(List<? extends T> revised, Patch<T> patch) {
 				return patch.restore(revised);
 		}
 
diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmFactory.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmFactory.java
index 307ee7e..5b9d71c 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmFactory.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmFactory.java
@@ -25,5 +25,5 @@
 public interface DiffAlgorithmFactory {
 		<T> DiffAlgorithmI<T> create();
 
-		<T> DiffAlgorithmI<T> create(BiPredicate<T, T> equalizer);
+		<T> DiffAlgorithmI<T> create(BiPredicate<? super T, ? super T> equalizer);
 }
diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmI.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmI.java
index a12b499..ee421c5 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmI.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/DiffAlgorithmI.java
@@ -34,7 +34,7 @@ public interface DiffAlgorithmI<T> {
 		 * @param progress progress listener
 		 * @return
 		 */
-		List<Change> computeDiff(List<T> source, List<T> target, DiffAlgorithmListener progress);
+		List<Change> computeDiff(List<? extends T> source, List<? extends T> target, DiffAlgorithmListener progress);
 
 		/**
 		 * Simple extension to compute a changeset using arrays.
diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiff.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiff.java
index 5233e02..c990208 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiff.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiff.java
@@ -31,13 +31,13 @@
  */
 public final class MyersDiff<T> implements DiffAlgorithmI<T> {
 
-		private final BiPredicate<T, T> equalizer;
+		private final BiPredicate<? super T, ? super T> equalizer;
 
 		public MyersDiff() {
 				equalizer = Object::equals;
 		}
 
-		public MyersDiff(final BiPredicate<T, T> equalizer) {
+		public MyersDiff(final BiPredicate<? super T, ? super T> equalizer) {
 				Objects.requireNonNull(equalizer, "equalizer must not be null");
 				this.equalizer = equalizer;
 		}
@@ -48,7 +48,8 @@ public MyersDiff(final BiPredicate<T, T> equalizer) {
 		 * Return empty diff if get the error while procession the difference.
 		 */
 		@Override
-		public List<Change> computeDiff(final List<T> source, final List<T> target, DiffAlgorithmListener progress) {
+		public List<Change> computeDiff(
+						final List<? extends T> source, final List<? extends T> target, DiffAlgorithmListener progress) {
 				Objects.requireNonNull(source, "source list must not be null");
 				Objects.requireNonNull(target, "target list must not be null");
 
@@ -71,9 +72,10 @@ public List<Change> computeDiff(final List<T> source, final List<T> target, Diff
 		 * @param orig The original sequence.
 		 * @param rev The revised sequence.
 		 * @return A minimum {@link PathNode Path} accross the differences graph.
-		 * @throws DifferentiationFailedException if a diff path could not be found.
+		 * @throws IllegalStateException if a diff path could not be found.
 		 */
-		private PathNode buildPath(final List<T> orig, final List<T> rev, DiffAlgorithmListener progress) {
+		private PathNode buildPath(
+						final List<? extends T> orig, final List<? extends T> rev, DiffAlgorithmListener progress) {
 				Objects.requireNonNull(orig, "original sequence is null");
 				Objects.requireNonNull(rev, "revised sequence is null");
 
@@ -140,10 +142,10 @@ private PathNode buildPath(final List<T> orig, final List<T> rev, DiffAlgorithmL
 		 * @param orig The original sequence.
 		 * @param rev The revised sequence.
 		 * @return A {@link Patch} script corresponding to the path.
-		 * @throws DifferentiationFailedException if a {@link Patch} could not be
+		 * @throws IllegalStateException if a {@link Patch} could not be
 		 * built from the given path.
 		 */
-		private List<Change> buildRevision(PathNode actualPath, List<T> orig, List<T> rev) {
+		private List<Change> buildRevision(PathNode actualPath, List<? extends T> orig, List<? extends T> rev) {
 				Objects.requireNonNull(actualPath, "path is null");
 				Objects.requireNonNull(orig, "original sequence is null");
 				Objects.requireNonNull(rev, "revised sequence is null");
@@ -190,7 +192,7 @@ public <T> DiffAlgorithmI<T> create() {
 						}
 
 						@Override
-						public <T> DiffAlgorithmI<T> create(BiPredicate<T, T> equalizer) {
+						public <T> DiffAlgorithmI<T> create(BiPredicate<? super T, ? super T> equalizer) {
 								return new MyersDiff<>(equalizer);
 						}
 				};
diff --git a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiffWithLinearSpace.java b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiffWithLinearSpace.java
index f8c734b..2e1a53c 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiffWithLinearSpace.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/algorithm/myers/MyersDiffWithLinearSpace.java
@@ -32,19 +32,20 @@
  */
 public class MyersDiffWithLinearSpace<T> implements DiffAlgorithmI<T> {
 
-		private final BiPredicate<T, T> equalizer;
+		private final BiPredicate<? super T, ? super T> equalizer;
 
 		public MyersDiffWithLinearSpace() {
 				equalizer = Object::equals;
 		}
 
-		public MyersDiffWithLinearSpace(final BiPredicate<T, T> equalizer) {
+		public MyersDiffWithLinearSpace(final BiPredicate<? super T, ? super T> equalizer) {
 				Objects.requireNonNull(equalizer, "equalizer must not be null");
 				this.equalizer = equalizer;
 		}
 
 		@Override
-		public List<Change> computeDiff(List<T> source, List<T> target, DiffAlgorithmListener progress) {
+		public List<Change> computeDiff(
+						List<? extends T> source, List<? extends T> target, DiffAlgorithmListener progress) {
 				Objects.requireNonNull(source, "source list must not be null");
 				Objects.requireNonNull(target, "target list must not be null");
 
@@ -200,10 +201,10 @@ private class DiffData {
 				final int[] vDown;
 				final int[] vUp;
 				final List<Change> script;
-				final List<T> source;
-				final List<T> target;
+				final List<? extends T> source;
+				final List<? extends T> target;
 
-				public DiffData(List<T> source, List<T> target) {
+				public DiffData(List<? extends T> source, List<? extends T> target) {
 						this.source = source;
 						this.target = target;
 						size = source.size() + target.size() + 2;
@@ -237,7 +238,7 @@ public <T> DiffAlgorithmI<T> create() {
 						}
 
 						@Override
-						public <T> DiffAlgorithmI<T> create(BiPredicate<T, T> equalizer) {
+						public <T> DiffAlgorithmI<T> create(BiPredicate<? super T, ? super T> equalizer) {
 								return new MyersDiffWithLinearSpace<>(equalizer);
 						}
 				};
diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java b/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java
index 64f0568..98cb561 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java
@@ -18,7 +18,7 @@
 import java.util.List;
 
 /**
- * This delta contains equal lines of data. Therefore nothing is to do in applyTo and restore.
+ * This delta contains equal lines of data. Therefore, nothing is to do in applyTo and restore.
  * @author tobens
  */
 public class EqualDelta<T> extends AbstractDelta<T> {
@@ -49,6 +49,6 @@ public String toString() {
 
 		@Override
 		public AbstractDelta<T> withChunks(Chunk<T> original, Chunk<T> revised) {
-				return new EqualDelta<T>(original, revised);
+				return new EqualDelta<>(original, revised);
 		}
 }
diff --git a/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java b/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java
index 6a54d82..31c2c3e 100644
--- a/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java
+++ b/java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java
@@ -54,7 +54,7 @@ public Patch(int estimatedPatchSize) {
 		 * @return A new list containing the applied patch.
 		 * @throws PatchFailedException if the patch cannot be applied
 		 */
-		public List<T> applyTo(List<T> target) throws PatchFailedException {
+		public List<T> applyTo(List<? extends T> target) throws PatchFailedException {
 				List<T> result = new ArrayList<>(target);
 				applyToExisting(result);
 				return result;
@@ -244,7 +244,7 @@ public Patch withConflictOutput(ConflictOutput<T> conflictOutput) {
 		 * @param target The list to copy and apply changes to.
 		 * @return A new list, containing the restored state.
 		 */
-		public List<T> restore(List<T> target) {
+		public List<T> restore(List<? extends T> target) {
 				List<T> result = new ArrayList<>(target);
 				restoreToExisting(result);
 				return result;
@@ -294,12 +294,12 @@ public static <T> Patch<T> generate(List<T> original, List<T> revised, List<Chan
 				return generate(original, revised, changes, false);
 		}
 
-		private static <T> Chunk<T> buildChunk(int start, int end, List<T> data) {
+		private static <T> Chunk<T> buildChunk(int start, int end, List<? extends T> data) {
 				return new Chunk<>(start, new ArrayList<>(data.subList(start, end)));
 		}
 
 		public static <T> Patch<T> generate(
-						List<T> original, List<T> revised, List<Change> _changes, boolean includeEquals) {
+						List<? extends T> original, List<? extends T> revised, List<Change> _changes, boolean includeEquals) {
 				Patch<T> patch = new Patch<>(_changes.size());
 				int startOriginal = 0;
 				int startRevised = 0;
diff --git a/pom.xml b/pom.xml
index e39a81d..d0d5b28 100644
--- a/pom.xml
+++ b/pom.xml
@@ -132,28 +132,28 @@
           <sourceDirectories>${project.build.sourceDirectory}</sourceDirectories>
           <checkstyleRules>
             <module name="Checker">
-              <module name="SuppressWarningsFilter" />
+              <module name="SuppressWarningsFilter"/>
               <module name="TreeWalker">
-                <module name="SuppressionCommentFilter" />
-                <module name="AvoidNestedBlocks" />
-                <module name="ConstantName" />
-                <module name="EmptyCatchBlock" />
-                <module name="EmptyStatement" />
-                <module name="MissingOverride" />
-                <module name="MultipleVariableDeclarations" />
-                <module name="ParameterAssignment" />
-                <module name="StringLiteralEquality" />
-                <module name="RedundantImport" />
-                <module name="UnusedImports" />
+                <module name="SuppressionCommentFilter"/>
+                <module name="AvoidNestedBlocks"/>
+                <module name="ConstantName"/>
+                <module name="EmptyCatchBlock"/>
+                <module name="EmptyStatement"/>
+                <module name="MissingOverride"/>
+                <module name="MultipleVariableDeclarations"/>
+                <module name="ParameterAssignment"/>
+                <module name="StringLiteralEquality"/>
+                <module name="RedundantImport"/>
+                <module name="UnusedImports"/>
 
-                <module name="WhitespaceAfter" />
+                <module name="WhitespaceAfter"/>
 
-                <module name="NeedBraces" />
-                <module name="UnnecessaryParentheses" />
-                <module name="LeftCurly" />
-                <module name="RightCurly" />
+                <module name="NeedBraces"/>
+                <module name="UnnecessaryParentheses"/>
+                <module name="LeftCurly"/>
+                <module name="RightCurly"/>
 
-                <module name="SuppressWarningsHolder" />
+                <module name="SuppressWarningsHolder"/>
               </module>
             </module>
           </checkstyleRules>
@@ -188,10 +188,10 @@
       <plugin>
         <groupId>com.diffplug.spotless</groupId>
         <artifactId>spotless-maven-plugin</artifactId>
-        <version>2.30.0</version>
+        <version>2.46.0</version>
         <configuration>
           <java>
-            <palantirJavaFormat />
+            <palantirJavaFormat/>
             <indent>
               <tabs>true</tabs>
               <spacesPerTab>2</spacesPerTab>