Use diamond operator when creating generic instances (#2104)

examples/android-proguard-example/src/com/google/gson/examples/android/GsonProguardExampleActivity.java

@@ -53,7 +53,7 @@ public void onCreate(Bundle icicle) {
   }
 
   private Cart buildCart() {
-    List<LineItem> lineItems = new ArrayList<LineItem>();
+    List<LineItem> lineItems = new ArrayList<>();
     lineItems.add(new LineItem("hammer", 1, 12000000, "USD"));
     return new Cart(lineItems, "Happy Buyer", "4111-1111-1111-1111");
   }

extras/src/main/java/com/google/gson/graph/GraphAdapterBuilder.java

@@ -48,7 +48,7 @@ public final class GraphAdapterBuilder {
   private final ConstructorConstructor constructorConstructor;
 
   public GraphAdapterBuilder() {
-      this.instanceCreators = new HashMap<Type, InstanceCreator<?>>();
+      this.instanceCreators = new HashMap<>();
       this.constructorConstructor = new ConstructorConstructor(instanceCreators, true, Collections.<ReflectionAccessFilter>emptyList());
   }
   public GraphAdapterBuilder addType(Type type) {
@@ -80,7 +80,7 @@ public void registerOn(GsonBuilder gsonBuilder) {
 
   static class Factory implements TypeAdapterFactory, InstanceCreator {
     private final Map<Type, InstanceCreator<?>> instanceCreators;
-    private final ThreadLocal<Graph> graphThreadLocal = new ThreadLocal<Graph>();
+    private final ThreadLocal<Graph> graphThreadLocal = new ThreadLocal<>();
 
     Factory(Map<Type, InstanceCreator<?>> instanceCreators) {
       this.instanceCreators = instanceCreators;
@@ -121,7 +121,7 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
           @SuppressWarnings("unchecked") // graph.map guarantees consistency between value and T
           Element<T> element = (Element<T>) graph.map.get(value);
           if (element == null) {
-            element = new Element<T>(value, graph.nextName(), typeAdapter, null);
+            element = new Element<>(value, graph.nextName(), typeAdapter, null);
             graph.map.put(value, element);
             graph.queue.add(element);
           }
@@ -178,7 +178,7 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
                 currentName = name;
               }
               JsonElement element = elementAdapter.read(in);
-              graph.map.put(name, new Element<T>(null, name, typeAdapter, element));
+              graph.map.put(name, new Element<>(null, name, typeAdapter, element));
             }
             in.endObject();
           } else {
@@ -242,7 +242,7 @@ static class Graph {
      * The queue of elements to write during serialization. Unused during
      * deserialization.
      */
-    private final Queue<Element> queue = new LinkedList<Element>();
+    private final Queue<Element> queue = new LinkedList<>();
 
     /**
      * The instance currently being deserialized. Used as a backdoor between

extras/src/main/java/com/google/gson/interceptors/InterceptorFactory.java

@@ -19,7 +19,7 @@ public final class InterceptorFactory implements TypeAdapterFactory {
     }
 
     TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
-    return new InterceptorAdapter<T>(delegate, intercept);
+    return new InterceptorAdapter<>(delegate, intercept);
   }
 
   static class InterceptorAdapter<T> extends TypeAdapter<T> {

extras/src/main/java/com/google/gson/typeadapters/PostConstructAdapterFactory.java

@@ -38,7 +38,7 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
                 if (m.isAnnotationPresent(PostConstruct.class)) {
                     m.setAccessible(true);
                     TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
-                    return new PostConstructAdapter<T>(delegate, m);
+                    return new PostConstructAdapter<>(delegate, m);
                 }
             }
         }

extras/src/main/java/com/google/gson/typeadapters/RuntimeTypeAdapterFactory.java

@@ -135,8 +135,8 @@
 public final class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
   private final Class<?> baseType;
   private final String typeFieldName;
-  private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<String, Class<?>>();
-  private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<Class<?>, String>();
+  private final Map<String, Class<?>> labelToSubtype = new LinkedHashMap<>();
+  private final Map<Class<?>, String> subtypeToLabel = new LinkedHashMap<>();
   private final boolean maintainType;
 
   private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boolean maintainType) {
@@ -154,23 +154,23 @@ private RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName, boole
    * {@code maintainType} flag decide if the type will be stored in pojo or not.
    */
   public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName, boolean maintainType) {
-    return new RuntimeTypeAdapterFactory<T>(baseType, typeFieldName, maintainType);
+    return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, maintainType);
   }
 
   /**
    * Creates a new runtime type adapter using for {@code baseType} using {@code
    * typeFieldName} as the type field name. Type field names are case sensitive.
    */
   public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType, String typeFieldName) {
-    return new RuntimeTypeAdapterFactory<T>(baseType, typeFieldName, false);
+    return new RuntimeTypeAdapterFactory<>(baseType, typeFieldName, false);
   }
 
   /**
    * Creates a new runtime type adapter for {@code baseType} using {@code "type"} as
    * the type field name.
    */
   public static <T> RuntimeTypeAdapterFactory<T> of(Class<T> baseType) {
-    return new RuntimeTypeAdapterFactory<T>(baseType, "type", false);
+    return new RuntimeTypeAdapterFactory<>(baseType, "type", false);
   }
 
   /**
@@ -210,10 +210,8 @@ public <R> TypeAdapter<R> create(Gson gson, TypeToken<R> type) {
     }
 
     final TypeAdapter<JsonElement> jsonElementAdapter = gson.getAdapter(JsonElement.class);
-    final Map<String, TypeAdapter<?>> labelToDelegate
-        = new LinkedHashMap<String, TypeAdapter<?>>();
-    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate
-        = new LinkedHashMap<Class<?>, TypeAdapter<?>>();
+    final Map<String, TypeAdapter<?>> labelToDelegate = new LinkedHashMap<>();
+    final Map<Class<?>, TypeAdapter<?>> subtypeToDelegate = new LinkedHashMap<>();
     for (Map.Entry<String, Class<?>> entry : labelToSubtype.entrySet()) {
       TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
       labelToDelegate.put(entry.getKey(), delegate);

extras/src/test/java/com/google/gson/graph/GraphAdapterBuilderTest.java

@@ -93,9 +93,9 @@ public void testSerializeListOfLists() {
     Type listOfListsType = new TypeToken<List<List<?>>>() {}.getType();
     Type listOfAnyType = new TypeToken<List<?>>() {}.getType();
 
-    List<List<?>> listOfLists = new ArrayList<List<?>>();
+    List<List<?>> listOfLists = new ArrayList<>();
     listOfLists.add(listOfLists);
-    listOfLists.add(new ArrayList<Object>());
+    listOfLists.add(new ArrayList<>());
 
     GsonBuilder gsonBuilder = new GsonBuilder();
     new GraphAdapterBuilder()
@@ -187,7 +187,7 @@ static class Employee {
 
   static class Company {
     final String name;
-    final List<Employee> employees = new ArrayList<Employee>();
+    final List<Employee> employees = new ArrayList<>();
     Company(String name) {
       this.name = name;
     }

gson/src/main/java/com/google/gson/Gson.java

@@ -128,9 +128,9 @@ public final class Gson {
    * The proxy is wired up once the initial adapter has been created.
    */
   private final ThreadLocal<Map<TypeToken<?>, FutureTypeAdapter<?>>> calls
-      = new ThreadLocal<Map<TypeToken<?>, FutureTypeAdapter<?>>>();
+      = new ThreadLocal<>();
 
-  private final Map<TypeToken<?>, TypeAdapter<?>> typeTokenCache = new ConcurrentHashMap<TypeToken<?>, TypeAdapter<?>>();
+  private final Map<TypeToken<?>, TypeAdapter<?>> typeTokenCache = new ConcurrentHashMap<>();
 
   private final ConstructorConstructor constructorConstructor;
   private final JsonAdapterAnnotationTypeAdapterFactory jsonAdapterFactory;
@@ -237,7 +237,7 @@ public Gson() {
     this.numberToNumberStrategy = numberToNumberStrategy;
     this.reflectionFilters = reflectionFilters;
 
-    List<TypeAdapterFactory> factories = new ArrayList<TypeAdapterFactory>();
+    List<TypeAdapterFactory> factories = new ArrayList<>();
 
     // built-in type adapters that cannot be overridden
     factories.add(TypeAdapters.JSON_ELEMENT_FACTORY);
@@ -453,7 +453,7 @@ private static TypeAdapter<AtomicLongArray> atomicLongArrayAdapter(final TypeAda
         out.endArray();
       }
       @Override public AtomicLongArray read(JsonReader in) throws IOException {
-        List<Long> list = new ArrayList<Long>();
+        List<Long> list = new ArrayList<>();
         in.beginArray();
         while (in.hasNext()) {
             long value = longAdapter.read(in).longValue();
@@ -486,7 +486,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     Map<TypeToken<?>, FutureTypeAdapter<?>> threadCalls = calls.get();
     boolean requiresThreadLocalCleanup = false;
     if (threadCalls == null) {
-      threadCalls = new HashMap<TypeToken<?>, FutureTypeAdapter<?>>();
+      threadCalls = new HashMap<>();
       calls.set(threadCalls);
       requiresThreadLocalCleanup = true;
     }
@@ -498,7 +498,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     }
 
     try {
-      FutureTypeAdapter<T> call = new FutureTypeAdapter<T>();
+      FutureTypeAdapter<T> call = new FutureTypeAdapter<>();
       threadCalls.put(type, call);
 
       for (TypeAdapterFactory factory : factories) {

gson/src/main/java/com/google/gson/GsonBuilder.java

@@ -84,11 +84,10 @@ public final class GsonBuilder {
   private Excluder excluder = Excluder.DEFAULT;
   private LongSerializationPolicy longSerializationPolicy = LongSerializationPolicy.DEFAULT;
   private FieldNamingStrategy fieldNamingPolicy = FieldNamingPolicy.IDENTITY;
-  private final Map<Type, InstanceCreator<?>> instanceCreators
-      = new HashMap<Type, InstanceCreator<?>>();
-  private final List<TypeAdapterFactory> factories = new ArrayList<TypeAdapterFactory>();
+  private final Map<Type, InstanceCreator<?>> instanceCreators = new HashMap<>();
+  private final List<TypeAdapterFactory> factories = new ArrayList<>();
   /** tree-style hierarchy factories. These come after factories for backwards compatibility. */
-  private final List<TypeAdapterFactory> hierarchyFactories = new ArrayList<TypeAdapterFactory>();
+  private final List<TypeAdapterFactory> hierarchyFactories = new ArrayList<>();
   private boolean serializeNulls = DEFAULT_SERIALIZE_NULLS;
   private String datePattern = DEFAULT_DATE_PATTERN;
   private int dateStyle = DateFormat.DEFAULT;
@@ -102,7 +101,7 @@ public final class GsonBuilder {
   private boolean useJdkUnsafe = DEFAULT_USE_JDK_UNSAFE;
   private ToNumberStrategy objectToNumberStrategy = DEFAULT_OBJECT_TO_NUMBER_STRATEGY;
   private ToNumberStrategy numberToNumberStrategy = DEFAULT_NUMBER_TO_NUMBER_STRATEGY;
-  private final LinkedList<ReflectionAccessFilter> reflectionFilters = new LinkedList<ReflectionAccessFilter>();
+  private final LinkedList<ReflectionAccessFilter> reflectionFilters = new LinkedList<>();
 
   /**
    * Creates a GsonBuilder instance that can be used to build Gson with various configuration
@@ -227,7 +226,7 @@ public GsonBuilder serializeNulls() {
    *       .enableComplexMapKeySerialization()
    *       .create();
    *
-   *   Map<Point, String> original = new LinkedHashMap<Point, String>();
+   *   Map<Point, String> original = new LinkedHashMap<>();
    *   original.put(new Point(5, 6), "a");
    *   original.put(new Point(8, 8), "b");
    *   System.out.println(gson.toJson(original, type));
@@ -254,7 +253,7 @@ public GsonBuilder serializeNulls() {
    *       .enableComplexMapKeySerialization()
    *       .create();
    *
-   *   Map<Point, String> original = new LinkedHashMap<Point, String>();
+   *   Map<Point, String> original = new LinkedHashMap<>();
    *   original.put(new Point(5, 6), "a");
    *   original.put(new Point(8, 8), "b");
    *   System.out.println(gson.toJson(original, type));
@@ -664,23 +663,23 @@ public GsonBuilder addReflectionAccessFilter(ReflectionAccessFilter filter) {
    * @return an instance of Gson configured with the options currently set in this builder
    */
   public Gson create() {
-    List<TypeAdapterFactory> factories = new ArrayList<TypeAdapterFactory>(this.factories.size() + this.hierarchyFactories.size() + 3);
+    List<TypeAdapterFactory> factories = new ArrayList<>(this.factories.size() + this.hierarchyFactories.size() + 3);
     factories.addAll(this.factories);
     Collections.reverse(factories);
 
-    List<TypeAdapterFactory> hierarchyFactories = new ArrayList<TypeAdapterFactory>(this.hierarchyFactories);
+    List<TypeAdapterFactory> hierarchyFactories = new ArrayList<>(this.hierarchyFactories);
     Collections.reverse(hierarchyFactories);
     factories.addAll(hierarchyFactories);
 
     addTypeAdaptersForDate(datePattern, dateStyle, timeStyle, factories);
 
-    return new Gson(excluder, fieldNamingPolicy, new HashMap<Type, InstanceCreator<?>>(instanceCreators),
+    return new Gson(excluder, fieldNamingPolicy, new HashMap<>(instanceCreators),
         serializeNulls, complexMapKeySerialization,
         generateNonExecutableJson, escapeHtmlChars, prettyPrinting, lenient,
         serializeSpecialFloatingPointValues, useJdkUnsafe, longSerializationPolicy,
-        datePattern, dateStyle, timeStyle, new ArrayList<TypeAdapterFactory>(this.factories),
-        new ArrayList<TypeAdapterFactory>(this.hierarchyFactories), factories,
-        objectToNumberStrategy, numberToNumberStrategy, new ArrayList<ReflectionAccessFilter>(reflectionFilters));
+        datePattern, dateStyle, timeStyle, new ArrayList<>(this.factories),
+        new ArrayList<>(this.hierarchyFactories), factories,
+        objectToNumberStrategy, numberToNumberStrategy, new ArrayList<>(reflectionFilters));
   }
 
   private void addTypeAdaptersForDate(String datePattern, int dateStyle, int timeStyle,

gson/src/main/java/com/google/gson/JsonArray.java

@@ -37,11 +37,11 @@ public final class JsonArray extends JsonElement implements Iterable<JsonElement
    * Creates an empty JsonArray.
    */
   public JsonArray() {
-    elements = new ArrayList<JsonElement>();
+    elements = new ArrayList<>();
   }
 
   public JsonArray(int capacity) {
-    elements = new ArrayList<JsonElement>(capacity);
+    elements = new ArrayList<>(capacity);
   }
 
   /**

gson/src/main/java/com/google/gson/JsonObject.java

@@ -30,8 +30,7 @@
  * @author Joel Leitch
  */
 public final class JsonObject extends JsonElement {
-  private final LinkedTreeMap<String, JsonElement> members =
-      new LinkedTreeMap<String, JsonElement>();
+  private final LinkedTreeMap<String, JsonElement> members = new LinkedTreeMap<>();
 
   /**
    * Creates a deep copy of this element and all its children

gson/src/main/java/com/google/gson/TypeAdapterFactory.java

@@ -35,7 +35,7 @@
  *         return null;
  *       }
  *
- *       final Map<String, T> lowercaseToConstant = new HashMap<String, T>();
+ *       final Map<String, T> lowercaseToConstant = new HashMap<>();
  *       for (T constant : rawType.getEnumConstants()) {
  *         lowercaseToConstant.put(toLowercase(constant), constant);
  *       }

gson/src/main/java/com/google/gson/internal/ConstructorConstructor.java

@@ -277,25 +277,25 @@ private static <T> ObjectConstructor<T> newDefaultImplementationConstructor(
       if (SortedSet.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new TreeSet<Object>();
+            return (T) new TreeSet<>();
           }
         };
       } else if (Set.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new LinkedHashSet<Object>();
+            return (T) new LinkedHashSet<>();
           }
         };
       } else if (Queue.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new ArrayDeque<Object>();
+            return (T) new ArrayDeque<>();
           }
         };
       } else {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new ArrayList<Object>();
+            return (T) new ArrayList<>();
           }
         };
       }
@@ -305,32 +305,32 @@ private static <T> ObjectConstructor<T> newDefaultImplementationConstructor(
       if (ConcurrentNavigableMap.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new ConcurrentSkipListMap<Object, Object>();
+            return (T) new ConcurrentSkipListMap<>();
           }
         };
       } else if (ConcurrentMap.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new ConcurrentHashMap<Object, Object>();
+            return (T) new ConcurrentHashMap<>();
           }
         };
       } else if (SortedMap.class.isAssignableFrom(rawType)) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new TreeMap<Object, Object>();
+            return (T) new TreeMap<>();
           }
         };
       } else if (type instanceof ParameterizedType && !(String.class.isAssignableFrom(
           TypeToken.get(((ParameterizedType) type).getActualTypeArguments()[0]).getRawType()))) {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new LinkedHashMap<Object, Object>();
+            return (T) new LinkedHashMap<>();
           }
         };
       } else {
         return new ObjectConstructor<T>() {
           @Override public T construct() {
-            return (T) new LinkedTreeMap<String, Object>();
+            return (T) new LinkedTreeMap<>();
           }
         };
       }

gson/src/main/java/com/google/gson/internal/Excluder.java

@@ -97,12 +97,11 @@ public Excluder withExclusionStrategy(ExclusionStrategy exclusionStrategy,
       boolean serialization, boolean deserialization) {
     Excluder result = clone();
     if (serialization) {
-      result.serializationStrategies = new ArrayList<ExclusionStrategy>(serializationStrategies);
+      result.serializationStrategies = new ArrayList<>(serializationStrategies);
       result.serializationStrategies.add(exclusionStrategy);
     }
     if (deserialization) {
-      result.deserializationStrategies
-          = new ArrayList<ExclusionStrategy>(deserializationStrategies);
+      result.deserializationStrategies = new ArrayList<>(deserializationStrategies);
       result.deserializationStrategies.add(exclusionStrategy);
     }
     return result;