- java.lang.Object
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- com.google.gson.reflect.TypeToken<T>
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public class TypeToken<T> extends Object
Represents a generic typeT
. Java doesn't yet provide a way to represent generic types, so this class does. Forces clients to create a subclass of this class which enables retrieval the type information even at runtime.For example, to create a type literal for
List<String>
, you can create an empty anonymous class:TypeToken<List<String>> list = new TypeToken<List<String>>() {};
Capturing a type variable as type argument of a
TypeToken
should be avoided. Due to type erasure the runtime type of a type variable is not available to Gson and therefore it cannot provide the functionality one might expect, which gives a false sense of type-safety at compilation time and can lead to an unexpectedClassCastException
at runtime.If the type arguments of the parameterized type are only available at runtime, for example when you want to create a
List<E>
based on aClass<E>
representing the element type, the methodgetParameterized(Type, Type...)
can be used.- Author:
- Bob Lee, Sven Mawson, Jesse Wilson
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Constructor Summary
Constructors Modifier Constructor Description protected
TypeToken()
Constructs a new type literal.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description boolean
equals(Object o)
static <T> TypeToken<T>
get(Class<T> type)
Gets type literal for the givenClass
instance.static TypeToken<?>
get(Type type)
Gets type literal for the givenType
instance.static TypeToken<?>
getArray(Type componentType)
Gets type literal for the array type whose elements are all instances ofcomponentType
.static TypeToken<?>
getParameterized(Type rawType, Type... typeArguments)
Gets a type literal for the parameterized type represented by applyingtypeArguments
torawType
.Class<? super T>
getRawType()
Returns the raw (non-generic) type for this type.Type
getType()
Gets underlyingType
instance.int
hashCode()
boolean
isAssignableFrom(TypeToken<?> token)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.boolean
isAssignableFrom(Class<?> cls)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.boolean
isAssignableFrom(Type from)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.String
toString()
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Constructor Detail
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TypeToken
protected TypeToken()
Constructs a new type literal. Derives represented class from type parameter.Clients create an empty anonymous subclass. Doing so embeds the type parameter in the anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.
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Method Detail
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getRawType
public final Class<? super T> getRawType()
Returns the raw (non-generic) type for this type.
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getType
public final Type getType()
Gets underlyingType
instance.
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isAssignableFrom
@Deprecated public boolean isAssignableFrom(Class<?> cls)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.Check if this type is assignable from the given class object.
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isAssignableFrom
@Deprecated public boolean isAssignableFrom(Type from)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.Check if this type is assignable from the given Type.
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isAssignableFrom
@Deprecated public boolean isAssignableFrom(TypeToken<?> token)
Deprecated.this implementation may be inconsistent with javac for types with wildcards.Check if this type is assignable from the given type token.
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get
public static <T> TypeToken<T> get(Class<T> type)
Gets type literal for the givenClass
instance.
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getParameterized
public static TypeToken<?> getParameterized(Type rawType, Type... typeArguments)
Gets a type literal for the parameterized type represented by applyingtypeArguments
torawType
. This is mainly intended for situations where the type arguments are not available at compile time. The following example shows how a type token forMap<K, V>
can be created:
As seen here the result is aClass<K> keyClass = ...; Class<V> valueClass = ...; TypeToken<?> mapTypeToken = TypeToken.getParameterized(Map.class, keyClass, valueClass);
TypeToken<?>
; this method cannot provide any type safety, and care must be taken to pass in the correct number of type arguments.- Throws:
IllegalArgumentException
- IfrawType
is not of typeClass
, or if the type arguments are invalid for the raw type
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