diff --git a/gson/src/test/java/com/google/gson/GsonBuilderTest.java b/gson/src/test/java/com/google/gson/GsonBuilderTest.java
index 2d9a63101d..cbebb1d619 100644
--- a/gson/src/test/java/com/google/gson/GsonBuilderTest.java
+++ b/gson/src/test/java/com/google/gson/GsonBuilderTest.java
@@ -38,7 +38,7 @@
  */
 public class GsonBuilderTest {
   private static final TypeAdapter<Object> NULL_TYPE_ADAPTER =
-      new TypeAdapter<Object>() {
+      new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, Object value) {
           throw new AssertionError();
diff --git a/gson/src/test/java/com/google/gson/GsonTest.java b/gson/src/test/java/com/google/gson/GsonTest.java
index e51259e781..8bfc69b45a 100644
--- a/gson/src/test/java/com/google/gson/GsonTest.java
+++ b/gson/src/test/java/com/google/gson/GsonTest.java
@@ -72,7 +72,7 @@ public void testOverridesDefaultExcluder() {
         new Gson(
             CUSTOM_EXCLUDER,
             CUSTOM_FIELD_NAMING_STRATEGY,
-            new HashMap<Type, InstanceCreator<?>>(),
+            new HashMap<>(),
             true,
             false,
             true,
@@ -85,12 +85,12 @@ public void testOverridesDefaultExcluder() {
             null,
             DateFormat.DEFAULT,
             DateFormat.DEFAULT,
-            new ArrayList<TypeAdapterFactory>(),
-            new ArrayList<TypeAdapterFactory>(),
-            new ArrayList<TypeAdapterFactory>(),
+            new ArrayList<>(),
+            new ArrayList<>(),
+            new ArrayList<>(),
             CUSTOM_OBJECT_TO_NUMBER_STRATEGY,
             CUSTOM_NUMBER_TO_NUMBER_STRATEGY,
-            Collections.<ReflectionAccessFilter>emptyList());
+            Collections.emptyList());
 
     assertThat(gson.excluder).isEqualTo(CUSTOM_EXCLUDER);
     assertThat(gson.fieldNamingStrategy()).isEqualTo(CUSTOM_FIELD_NAMING_STRATEGY);
@@ -104,7 +104,7 @@ public void testClonedTypeAdapterFactoryListsAreIndependent() {
         new Gson(
             CUSTOM_EXCLUDER,
             CUSTOM_FIELD_NAMING_STRATEGY,
-            new HashMap<Type, InstanceCreator<?>>(),
+            new HashMap<>(),
             true,
             false,
             true,
@@ -117,12 +117,12 @@ public void testClonedTypeAdapterFactoryListsAreIndependent() {
             null,
             DateFormat.DEFAULT,
             DateFormat.DEFAULT,
-            new ArrayList<TypeAdapterFactory>(),
-            new ArrayList<TypeAdapterFactory>(),
-            new ArrayList<TypeAdapterFactory>(),
+            new ArrayList<>(),
+            new ArrayList<>(),
+            new ArrayList<>(),
             CUSTOM_OBJECT_TO_NUMBER_STRATEGY,
             CUSTOM_NUMBER_TO_NUMBER_STRATEGY,
-            Collections.<ReflectionAccessFilter>emptyList());
+            Collections.emptyList());
 
     Gson clone =
         original.newBuilder().registerTypeAdapter(int.class, new TestTypeAdapter()).create();
diff --git a/gson/src/test/java/com/google/gson/GsonTypeAdapterTest.java b/gson/src/test/java/com/google/gson/GsonTypeAdapterTest.java
index fcf46238aa..5b4fb49907 100644
--- a/gson/src/test/java/com/google/gson/GsonTypeAdapterTest.java
+++ b/gson/src/test/java/com/google/gson/GsonTypeAdapterTest.java
@@ -152,7 +152,7 @@ private static void assertSerialized(
       boolean registerAbstractHierarchyDeserializer,
       Object instance) {
     JsonDeserializer<Abstract> deserializer =
-        new JsonDeserializer<Abstract>() {
+        new JsonDeserializer<>() {
           @Override
           public Abstract deserialize(
               JsonElement json, Type typeOfT, JsonDeserializationContext context)
diff --git a/gson/src/test/java/com/google/gson/JsonArrayAsListTest.java b/gson/src/test/java/com/google/gson/JsonArrayAsListTest.java
index 4f2577ce6c..a9a62eba1d 100644
--- a/gson/src/test/java/com/google/gson/JsonArrayAsListTest.java
+++ b/gson/src/test/java/com/google/gson/JsonArrayAsListTest.java
@@ -83,7 +83,7 @@ public void testAdd() {
     assertThat(list.add(JsonNull.INSTANCE)).isTrue();
 
     List<JsonElement> expectedList =
-        Arrays.<JsonElement>asList(
+        Arrays.asList(
             new JsonPrimitive(2),
             new JsonPrimitive(3),
             new JsonPrimitive(1),
@@ -111,21 +111,18 @@ public void testAddAll() {
     list.addAll(Arrays.asList(new JsonPrimitive(2), new JsonPrimitive(3)));
 
     List<JsonElement> expectedList =
-        Arrays.<JsonElement>asList(
-            new JsonPrimitive(1), new JsonPrimitive(2), new JsonPrimitive(3));
+        Arrays.asList(new JsonPrimitive(1), new JsonPrimitive(2), new JsonPrimitive(3));
     assertThat(list).isEqualTo(expectedList);
     assertThat(list).isEqualTo(expectedList);
 
     NullPointerException e =
         assertThrows(
-            NullPointerException.class,
-            () -> list.addAll(0, Collections.<JsonElement>singletonList(null)));
+            NullPointerException.class, () -> list.addAll(0, Collections.singletonList(null)));
     assertThat(e).hasMessageThat().isEqualTo("Element must be non-null");
 
     e =
         assertThrows(
-            NullPointerException.class,
-            () -> list.addAll(Collections.<JsonElement>singletonList(null)));
+            NullPointerException.class, () -> list.addAll(Collections.singletonList(null)));
     assertThat(e).hasMessageThat().isEqualTo("Element must be non-null");
   }
 
diff --git a/gson/src/test/java/com/google/gson/JsonObjectAsMapTest.java b/gson/src/test/java/com/google/gson/JsonObjectAsMapTest.java
index cdaca0b516..55d045cbe2 100644
--- a/gson/src/test/java/com/google/gson/JsonObjectAsMapTest.java
+++ b/gson/src/test/java/com/google/gson/JsonObjectAsMapTest.java
@@ -148,15 +148,12 @@ public void testPutAll() {
     var e =
         assertThrows(
             NullPointerException.class,
-            () ->
-                map.putAll(
-                    Collections.<String, JsonElement>singletonMap(null, new JsonPrimitive(1))));
+            () -> map.putAll(Collections.singletonMap(null, new JsonPrimitive(1))));
     assertThat(e).hasMessageThat().isEqualTo("key == null");
 
     e =
         assertThrows(
-            NullPointerException.class,
-            () -> map.putAll(Collections.<String, JsonElement>singletonMap("a", null)));
+            NullPointerException.class, () -> map.putAll(Collections.singletonMap("a", null)));
     assertThat(e).hasMessageThat().isEqualTo("value == null");
   }
 
@@ -221,7 +218,7 @@ public void testEntrySet() {
     Set<Entry<String, JsonElement>> entrySet = map.entrySet();
 
     List<Entry<?, ?>> expectedEntrySet =
-        Arrays.<Entry<?, ?>>asList(
+        Arrays.asList(
             new SimpleEntry<>("b", new JsonPrimitive(2)),
             new SimpleEntry<>("a", new JsonPrimitive(1)));
     // Should contain entries in same order
diff --git a/gson/src/test/java/com/google/gson/OverrideCoreTypeAdaptersTest.java b/gson/src/test/java/com/google/gson/OverrideCoreTypeAdaptersTest.java
index a34f35f0ca..134abe1571 100644
--- a/gson/src/test/java/com/google/gson/OverrideCoreTypeAdaptersTest.java
+++ b/gson/src/test/java/com/google/gson/OverrideCoreTypeAdaptersTest.java
@@ -31,7 +31,7 @@
  */
 public class OverrideCoreTypeAdaptersTest {
   private static final TypeAdapter<Boolean> booleanAsIntAdapter =
-      new TypeAdapter<Boolean>() {
+      new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, Boolean value) throws IOException {
           out.value(value ? 1 : 0);
@@ -45,7 +45,7 @@ public Boolean read(JsonReader in) throws IOException {
       };
 
   private static final TypeAdapter<String> swapCaseStringAdapter =
-      new TypeAdapter<String>() {
+      new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, String value) throws IOException {
           out.value(value.toUpperCase(Locale.US));
diff --git a/gson/src/test/java/com/google/gson/TypeAdapterTest.java b/gson/src/test/java/com/google/gson/TypeAdapterTest.java
index 8a551adb85..e5aa8a422a 100644
--- a/gson/src/test/java/com/google/gson/TypeAdapterTest.java
+++ b/gson/src/test/java/com/google/gson/TypeAdapterTest.java
@@ -53,7 +53,7 @@ public String read(JsonReader in) {
   public void testToJson_ThrowingIOException() {
     final IOException exception = new IOException("test");
     TypeAdapter<Integer> adapter =
-        new TypeAdapter<Integer>() {
+        new TypeAdapter<>() {
           @Override
           public void write(JsonWriter out, Integer value) throws IOException {
             throw exception;
@@ -73,7 +73,7 @@ public Integer read(JsonReader in) {
   }
 
   private static final TypeAdapter<String> adapter =
-      new TypeAdapter<String>() {
+      new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, String value) throws IOException {
           out.value(value);
diff --git a/gson/src/test/java/com/google/gson/functional/DelegateTypeAdapterTest.java b/gson/src/test/java/com/google/gson/functional/DelegateTypeAdapterTest.java
index 99401266cb..8c837fa051 100644
--- a/gson/src/test/java/com/google/gson/functional/DelegateTypeAdapterTest.java
+++ b/gson/src/test/java/com/google/gson/functional/DelegateTypeAdapterTest.java
@@ -78,7 +78,7 @@ private static class StatsTypeAdapterFactory implements TypeAdapterFactory {
     @Override
     public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
       final TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
-      return new TypeAdapter<T>() {
+      return new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, T value) throws IOException {
           ++numWrites;
diff --git a/gson/src/test/java/com/google/gson/functional/FormattingStyleTest.java b/gson/src/test/java/com/google/gson/functional/FormattingStyleTest.java
index fa07a3c9fd..581b23e55b 100644
--- a/gson/src/test/java/com/google/gson/functional/FormattingStyleTest.java
+++ b/gson/src/test/java/com/google/gson/functional/FormattingStyleTest.java
@@ -73,8 +73,7 @@ public void testDefault() {
   public void testVariousCombinationsParse() {
     // Mixing various indent and newline styles in the same string, to be parsed.
     String jsonStringMix = "{\r\t'a':\r\n[        1,2\t]\n}";
-    TypeToken<Map<String, List<Integer>>> inputType =
-        new TypeToken<Map<String, List<Integer>>>() {};
+    TypeToken<Map<String, List<Integer>>> inputType = new TypeToken<>() {};
 
     Map<String, List<Integer>> actualParsed;
     // Test all that all combinations of newline can be parsed and generate the same INPUT.
diff --git a/gson/src/test/java/com/google/gson/functional/InstanceCreatorTest.java b/gson/src/test/java/com/google/gson/functional/InstanceCreatorTest.java
index 54a9fedce2..5a76b9f175 100644
--- a/gson/src/test/java/com/google/gson/functional/InstanceCreatorTest.java
+++ b/gson/src/test/java/com/google/gson/functional/InstanceCreatorTest.java
@@ -106,7 +106,7 @@ public void testInstanceCreatorForCollectionType() {
     @SuppressWarnings("serial")
     class SubArrayList<T> extends ArrayList<T> {}
     InstanceCreator<List<String>> listCreator =
-        new InstanceCreator<List<String>>() {
+        new InstanceCreator<>() {
           @Override
           public List<String> createInstance(Type type) {
             return new SubArrayList<>();
@@ -124,7 +124,7 @@ public void testInstanceCreatorForParametrizedType() {
     @SuppressWarnings("serial")
     class SubTreeSet<T> extends TreeSet<T> {}
     InstanceCreator<SortedSet<?>> sortedSetCreator =
-        new InstanceCreator<SortedSet<?>>() {
+        new InstanceCreator<>() {
           @Override
           public SortedSet<?> createInstance(Type type) {
             return new SubTreeSet<>();
diff --git a/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnClassesTest.java b/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnClassesTest.java
index 97febb8367..081b869e93 100644
--- a/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnClassesTest.java
+++ b/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnClassesTest.java
@@ -78,7 +78,7 @@ public void testJsonAdapterFactoryInvoked() {
   @Test
   public void testRegisteredAdapterOverridesJsonAdapter() {
     TypeAdapter<A> typeAdapter =
-        new TypeAdapter<A>() {
+        new TypeAdapter<>() {
           @Override
           public void write(JsonWriter out, A value) throws IOException {
             out.value("registeredAdapter");
@@ -98,7 +98,7 @@ public A read(JsonReader in) throws IOException {
   @Test
   public void testRegisteredSerializerOverridesJsonAdapter() {
     JsonSerializer<A> serializer =
-        new JsonSerializer<A>() {
+        new JsonSerializer<>() {
           @Override
           public JsonElement serialize(A src, Type typeOfSrc, JsonSerializationContext context) {
             return new JsonPrimitive("registeredSerializer");
@@ -115,7 +115,7 @@ public JsonElement serialize(A src, Type typeOfSrc, JsonSerializationContext con
   @Test
   public void testRegisteredDeserializerOverridesJsonAdapter() {
     JsonDeserializer<A> deserializer =
-        new JsonDeserializer<A>() {
+        new JsonDeserializer<>() {
           @Override
           public A deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
               throws JsonParseException {
@@ -170,8 +170,7 @@ public void testFactoryReturningNull() {
     assertThat(gson.fromJson("null", WithNullReturningFactory.class)).isNull();
     assertThat(gson.toJson(null, WithNullReturningFactory.class)).isEqualTo("null");
 
-    TypeToken<WithNullReturningFactory<String>> stringTypeArg =
-        new TypeToken<WithNullReturningFactory<String>>() {};
+    TypeToken<WithNullReturningFactory<String>> stringTypeArg = new TypeToken<>() {};
     WithNullReturningFactory<?> deserialized = gson.fromJson("\"a\"", stringTypeArg);
     assertThat(deserialized.t).isEqualTo("custom-read:a");
     assertThat(gson.fromJson("null", stringTypeArg)).isNull();
@@ -181,8 +180,7 @@ public void testFactoryReturningNull() {
 
     // Factory should return `null` for this type and Gson should fall back to reflection-based
     // adapter
-    TypeToken<WithNullReturningFactory<Integer>> numberTypeArg =
-        new TypeToken<WithNullReturningFactory<Integer>>() {};
+    TypeToken<WithNullReturningFactory<Integer>> numberTypeArg = new TypeToken<>() {};
     deserialized = gson.fromJson("{\"t\":1}", numberTypeArg);
     assertThat(deserialized.t).isEqualTo(1);
     assertThat(gson.toJson(new WithNullReturningFactory<>(2), numberTypeArg.getType()))
@@ -266,7 +264,7 @@ private static class C {
     static final class JsonAdapterFactory implements TypeAdapterFactory {
       @Override
       public <T> TypeAdapter<T> create(Gson gson, final TypeToken<T> type) {
-        return new TypeAdapter<T>() {
+        return new TypeAdapter<>() {
           @Override
           public void write(JsonWriter out, T value) throws IOException {
             out.value("jsonAdapterFactory");
@@ -428,7 +426,7 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
 
         TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
 
-        return new TypeAdapter<T>() {
+        return new TypeAdapter<>() {
           @Override
           public T read(JsonReader in) throws IOException {
             // Perform custom deserialization
@@ -478,7 +476,7 @@ private static class WithDelayedDelegatingFactory {
     static class Factory implements TypeAdapterFactory {
       @Override
       public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
-        return new TypeAdapter<T>() {
+        return new TypeAdapter<>() {
           // suppress Error Prone warning; should be clear that `Factory` refers to enclosing class
           @SuppressWarnings("SameNameButDifferent")
           private TypeAdapter<T> delegate() {
@@ -670,7 +668,7 @@ static class Factory implements TypeAdapterFactory {
       public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
         TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
 
-        return new TypeAdapter<T>() {
+        return new TypeAdapter<>() {
           @Override
           public T read(JsonReader in) throws IOException {
             // Perform custom deserialization
diff --git a/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnFieldsTest.java b/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnFieldsTest.java
index a5d355f054..277babad74 100644
--- a/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnFieldsTest.java
+++ b/gson/src/test/java/com/google/gson/functional/JsonAdapterAnnotationOnFieldsTest.java
@@ -147,7 +147,7 @@ public Part read(JsonReader in) throws IOException {
   private static class GizmoPartTypeAdapterFactory implements TypeAdapterFactory {
     @Override
     public <T> TypeAdapter<T> create(Gson gson, final TypeToken<T> type) {
-      return new TypeAdapter<T>() {
+      return new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, T value) throws IOException {
           out.value("GizmoPartTypeAdapterFactory");
@@ -303,7 +303,7 @@ private GadgetWithPrimitivePart(long part) {
 
   private static final class LongToStringTypeAdapterFactory implements TypeAdapterFactory {
     static final TypeAdapter<Long> ADAPTER =
-        new TypeAdapter<Long>() {
+        new TypeAdapter<>() {
           @Override
           public void write(JsonWriter out, Long value) throws IOException {
             out.value(value.toString());
@@ -352,7 +352,7 @@ private static final class Gizmo2 {
   private static class Gizmo2PartTypeAdapterFactory implements TypeAdapterFactory {
     @Override
     public <T> TypeAdapter<T> create(Gson gson, final TypeToken<T> type) {
-      return new TypeAdapter<T>() {
+      return new TypeAdapter<>() {
         @Override
         public void write(JsonWriter out, T value) throws IOException {
           out.value("GizmoPartTypeAdapterFactory");
diff --git a/gson/src/test/java/com/google/gson/functional/MapTest.java b/gson/src/test/java/com/google/gson/functional/MapTest.java
index 689bbedc2d..293178c607 100644
--- a/gson/src/test/java/com/google/gson/functional/MapTest.java
+++ b/gson/src/test/java/com/google/gson/functional/MapTest.java
@@ -526,7 +526,7 @@ public final void testInterfaceTypeMapWithSerializer() {
         "{\"bases\":{\"Test\":" + baseTypeJson + "},\"subs\":{\"Test\":" + subTypeJson + "}}";
 
     JsonSerializer<TestTypes.Base> baseTypeAdapter =
-        new JsonSerializer<TestTypes.Base>() {
+        new JsonSerializer<>() {
           @Override
           public JsonElement serialize(
               TestTypes.Base src, Type typeOfSrc, JsonSerializationContext context) {
diff --git a/gson/src/test/java/com/google/gson/functional/ParameterizedTypesTest.java b/gson/src/test/java/com/google/gson/functional/ParameterizedTypesTest.java
index 42e77840e3..b408544d5e 100644
--- a/gson/src/test/java/com/google/gson/functional/ParameterizedTypesTest.java
+++ b/gson/src/test/java/com/google/gson/functional/ParameterizedTypesTest.java
@@ -120,11 +120,11 @@ public void testParameterizedTypeWithCustomSerializer() {
             .create();
     MyParameterizedType<Integer> intTarget = new MyParameterizedType<>(10);
     String json = gson.toJson(intTarget, ptIntegerType);
-    assertThat(json).isEqualTo(MyParameterizedTypeAdapter.<Integer>getExpectedJson(intTarget));
+    assertThat(json).isEqualTo(MyParameterizedTypeAdapter.getExpectedJson(intTarget));
 
     MyParameterizedType<String> stringTarget = new MyParameterizedType<>("abc");
     json = gson.toJson(stringTarget, ptStringType);
-    assertThat(json).isEqualTo(MyParameterizedTypeAdapter.<String>getExpectedJson(stringTarget));
+    assertThat(json).isEqualTo(MyParameterizedTypeAdapter.getExpectedJson(stringTarget));
   }
 
   @Test
@@ -140,12 +140,12 @@ public void testParameterizedTypesWithCustomDeserializer() {
             .create();
 
     MyParameterizedType<Integer> src = new MyParameterizedType<>(10);
-    String json = MyParameterizedTypeAdapter.<Integer>getExpectedJson(src);
+    String json = MyParameterizedTypeAdapter.getExpectedJson(src);
     MyParameterizedType<Integer> intTarget = gson.fromJson(json, ptIntegerType);
     assertThat(intTarget.value).isEqualTo(10);
 
     MyParameterizedType<String> srcStr = new MyParameterizedType<>("abc");
-    json = MyParameterizedTypeAdapter.<String>getExpectedJson(srcStr);
+    json = MyParameterizedTypeAdapter.getExpectedJson(srcStr);
     MyParameterizedType<String> stringTarget = gson.fromJson(json, ptStringType);
     assertThat(stringTarget.value).isEqualTo("abc");
   }
@@ -515,7 +515,7 @@ private static void assertCorrectlyDeserialized(Object object) {
 
   @Test
   public void testGsonFromJsonTypeToken() {
-    TypeToken<List<Quantity>> typeToken = new TypeToken<List<Quantity>>() {};
+    TypeToken<List<Quantity>> typeToken = new TypeToken<>() {};
     Type type = typeToken.getType();
 
     {
diff --git a/gson/src/test/java/com/google/gson/functional/RuntimeTypeAdapterFactoryFunctionalTest.java b/gson/src/test/java/com/google/gson/functional/RuntimeTypeAdapterFactoryFunctionalTest.java
index 667d231f36..3fae2da586 100644
--- a/gson/src/test/java/com/google/gson/functional/RuntimeTypeAdapterFactoryFunctionalTest.java
+++ b/gson/src/test/java/com/google/gson/functional/RuntimeTypeAdapterFactoryFunctionalTest.java
@@ -174,7 +174,7 @@ public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
         subtypeToDelegate.put(entry.getValue(), delegate);
       }
 
-      return new TypeAdapter<R>() {
+      return new TypeAdapter<>() {
         @Override
         public R read(JsonReader in) {
           JsonElement jsonElement = Streams.parse(in);
diff --git a/gson/src/test/java/com/google/gson/functional/StreamingTypeAdaptersTest.java b/gson/src/test/java/com/google/gson/functional/StreamingTypeAdaptersTest.java
index f7bdf3bb14..c6245cb27a 100644
--- a/gson/src/test/java/com/google/gson/functional/StreamingTypeAdaptersTest.java
+++ b/gson/src/test/java/com/google/gson/functional/StreamingTypeAdaptersTest.java
@@ -118,7 +118,7 @@ public void testDeserializeWithCustomTypeAdapter() throws IOException {
 
   private void usePersonNameAdapter() {
     TypeAdapter<Person> personNameAdapter =
-        new TypeAdapter<Person>() {
+        new TypeAdapter<>() {
           @Override
           public Person read(JsonReader in) throws IOException {
             String name = in.nextString();
@@ -181,7 +181,7 @@ public void testDeserialize2dArray() throws IOException {
   @Test
   public void testNullSafe() {
     TypeAdapter<Person> typeAdapter =
-        new TypeAdapter<Person>() {
+        new TypeAdapter<>() {
           @Override
           public Person read(JsonReader in) throws IOException {
             List<String> values = Splitter.on(',').splitToList(in.nextString());
diff --git a/gson/src/test/java/com/google/gson/functional/TreeTypeAdaptersTest.java b/gson/src/test/java/com/google/gson/functional/TreeTypeAdaptersTest.java
index 2aa043f424..6e9debbb0c 100644
--- a/gson/src/test/java/com/google/gson/functional/TreeTypeAdaptersTest.java
+++ b/gson/src/test/java/com/google/gson/functional/TreeTypeAdaptersTest.java
@@ -141,7 +141,7 @@ private static class Course<T> {
     private final Assignment<T> assignment;
 
     private Course() {
-      this(null, 0, null, new ArrayList<Student>());
+      this(null, 0, null, new ArrayList<>());
     }
 
     public Course(
diff --git a/gson/src/test/java/com/google/gson/functional/TypeAdapterPrecedenceTest.java b/gson/src/test/java/com/google/gson/functional/TypeAdapterPrecedenceTest.java
index 0252ec5052..52d04d9ba2 100644
--- a/gson/src/test/java/com/google/gson/functional/TypeAdapterPrecedenceTest.java
+++ b/gson/src/test/java/com/google/gson/functional/TypeAdapterPrecedenceTest.java
@@ -140,7 +140,7 @@ private Foo(String name) {
   }
 
   private static JsonSerializer<Foo> newSerializer(final String name) {
-    return new JsonSerializer<Foo>() {
+    return new JsonSerializer<>() {
       @Override
       public JsonElement serialize(Foo src, Type typeOfSrc, JsonSerializationContext context) {
         return new JsonPrimitive(src.name + " via " + name);
@@ -149,7 +149,7 @@ public JsonElement serialize(Foo src, Type typeOfSrc, JsonSerializationContext c
   }
 
   private static JsonDeserializer<Foo> newDeserializer(final String name) {
-    return new JsonDeserializer<Foo>() {
+    return new JsonDeserializer<>() {
       @Override
       public Foo deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) {
         return new Foo(json.getAsString() + " via " + name);
@@ -158,7 +158,7 @@ public Foo deserialize(JsonElement json, Type typeOfT, JsonDeserializationContex
   }
 
   private static TypeAdapter<Foo> newTypeAdapter(final String name) {
-    return new TypeAdapter<Foo>() {
+    return new TypeAdapter<>() {
       @Override
       public Foo read(JsonReader in) throws IOException {
         return new Foo(in.nextString() + " via " + name);
diff --git a/gson/src/test/java/com/google/gson/functional/TypeHierarchyAdapterTest.java b/gson/src/test/java/com/google/gson/functional/TypeHierarchyAdapterTest.java
index 973afb04ac..151863deef 100644
--- a/gson/src/test/java/com/google/gson/functional/TypeHierarchyAdapterTest.java
+++ b/gson/src/test/java/com/google/gson/functional/TypeHierarchyAdapterTest.java
@@ -201,7 +201,7 @@ public Employee deserialize(JsonElement json, Type typeOfT, JsonDeserializationC
         result = new Employee();
       }
       result.userid = context.deserialize(object.get("userid"), String.class);
-      result.startDate = context.<Long>deserialize(object.get("startDate"), long.class);
+      result.startDate = context.deserialize(object.get("startDate"), long.class);
       return result;
     }
   }
diff --git a/gson/src/test/java/com/google/gson/functional/TypeVariableTest.java b/gson/src/test/java/com/google/gson/functional/TypeVariableTest.java
index d1076fdb15..af1957e159 100644
--- a/gson/src/test/java/com/google/gson/functional/TypeVariableTest.java
+++ b/gson/src/test/java/com/google/gson/functional/TypeVariableTest.java
@@ -43,7 +43,7 @@ public void testAdvancedTypeVariables() {
     arrayList.add(2);
     arrayList.add(3);
     bar1.map.put("key1", arrayList);
-    bar1.map.put("key2", new ArrayList<Integer>());
+    bar1.map.put("key2", new ArrayList<>());
     String json = gson.toJson(bar1);
 
     Bar bar2 = gson.fromJson(json, Bar.class);
diff --git a/gson/src/test/java/com/google/gson/reflect/TypeTokenTest.java b/gson/src/test/java/com/google/gson/reflect/TypeTokenTest.java
index fa3a7a0ed7..d0e13805cd 100644
--- a/gson/src/test/java/com/google/gson/reflect/TypeTokenTest.java
+++ b/gson/src/test/java/com/google/gson/reflect/TypeTokenTest.java
@@ -328,7 +328,7 @@ class SubSubTypeToken2 extends SubTypeToken<Integer> {}
   }
 
   private static <M> void createTypeTokenTypeVariable() {
-    TypeToken<M> unused = new TypeToken<M>() {};
+    var unused = new TypeToken<M>() {};
   }
 
   /**