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TypeUtils

public class org.apache.commons.lang3.reflect.TypeUtils

Utility methods focusing on type inspection, particularly with regard to generics.

Since:

3.0

Constructors

TypeUtils()

Deprecated. TypeUtils instances should NOT be constructed in standard programming.

@Deprecated public TypeUtils()

Deprecated: TODO Make private in 4.0.

TypeUtils instances should NOT be constructed in standard programming. Instead, the class should be used as TypeUtils.isAssignable(cls, toClass).

This constructor is public to permit tools that require a JavaBean instance to operate.

Fields and constants

WILDCARD_ALL

A wildcard instance matching ?.

public static final WildcardType WILDCARD_ALL

A wildcard instance matching ?.

Since:

3.2

Methods

containsTypeVariables(Type)	Tests, recursively, whether any of the type parameters associated with type are bound to variables.
determineTypeArguments(Class, ParameterizedType)	Tries to determine the type arguments of a class/interface based on a super parameterized type’s type arguments.
equals(Type, Type)	Tests whether the given types are equal.
genericArrayType(Type)	Creates a generic array type instance.
getArrayComponentType(Type)	Gets the array component type of type.
getImplicitBounds(TypeVariable)	Gets an array containing the sole type of Object if TypeVariable#getBounds() returns an empty array.
getImplicitLowerBounds(WildcardType)	Gets an array containing a single value of null if WildcardType#getLowerBounds() returns an empty array.
getImplicitUpperBounds(WildcardType)	Gets an array containing the sole value of Object if WildcardType#getUpperBounds() returns an empty array.
getRawType(Type, Type)	Gets the raw type of a Java type, given its context.
getTypeArguments(ParameterizedType)	Gets all the type arguments for this parameterized type including owner hierarchy arguments such as Outer<K, V>.Inner<T>.DeepInner<E> .
getTypeArguments(Type, Class)	Gets the type arguments of a class/interface based on a subtype.
isArrayType(Type)	Tests whether the specified type denotes an array type.
isAssignable(Type, Type)	Tests if the subject type may be implicitly cast to the target type following the Java generics rules.
isInstance(Object, Type)	Tests if the given value can be assigned to the target type following the Java generics rules.
normalizeUpperBounds(Type[])	Strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).
parameterize(Class, Type[])	Creates a parameterized type instance.
parameterize(Class, Map)	Creates a parameterized type instance.
parameterizeWithOwner(Type, Class, Type[])	Creates a parameterized type instance.
parameterizeWithOwner(Type, Class, Map)	Creates a parameterized type instance.
toLongString(TypeVariable)	Formats a TypeVariable including its GenericDeclaration.
toString(Type)	Formats a given type as a Java-esque String.
typesSatisfyVariables(Map)	Determines whether or not specified types satisfy the bounds of their mapped type variables.
unrollVariables(Map, Type)	Gets a type representing type with variable assignments “unrolled.”
wildcardType()	Creates a new WildcardTypeBuilder.
wrap(Class)	Wraps the specified Class in a Typed wrapper.
wrap(Type)	Wraps the specified Type in a Typed wrapper.

public static boolean containsTypeVariables(Type type)

Tests, recursively, whether any of the type parameters associated with type are bound to variables.

Parameters:

type – The type to check for type variables.

Returns:

Whether any of the type parameters associated with type are bound to variables.

Since:

3.2

public static Map<TypeVariable<?>, Type> determineTypeArguments(Class<?> cls, ParameterizedType superParameterizedType)

Tries to determine the type arguments of a class/interface based on a super parameterized type’s type arguments. This method is the inverse of #getTypeArguments(Type, Class) which gets a class/interface’s type arguments based on a subtype. It is far more limited in determining the type arguments for the subject class’s type variables in that it can only determine those parameters that map from the subject Class object to the supertype.

Example: TreeSet sets its parameter as the parameter for NavigableSet, which in turn sets the parameter of java.util.SortedSet, which in turn sets the parameter of Set, which in turn sets the parameter of java.util.Collection, which in turn sets the parameter of Iterable. Since TreeSet’s parameter maps (indirectly) to Iterable’s parameter, it will be able to determine that based on the super type Iterable<? extends Map<Integer, ? extends Collection<?>>>, the parameter of TreeSet is ? extends Map<Integer, ? extends Collection<?>>.

Parameters:

• cls – The class whose type parameters are to be determined, not null.

• superParameterizedType – The super type from which cls’s type arguments are to be determined, not null.

Returns:

A Map of the type assignments that could be determined for the type variables in each type in the inheritance hierarchy from type to toClass inclusive.

Throws:

java.lang.NullPointerException – Thrown if either cls or superParameterizedType is null.

public static boolean equals(Type type1, Type type2)

Tests whether the given types are equal.

Parameters:

• type1 – The first type.

• type2 – The second type.

Returns:

Whether the given types are equal.

Since:

3.2

public static GenericArrayType genericArrayType(Type componentType)

Creates a generic array type instance.

Parameters:

componentType – The type of the elements of the array. For example the component type of boolean[] is boolean.

Returns:

GenericArrayType.

Since:

3.2

public static Type getArrayComponentType(Type type)

Gets the array component type of type.

Parameters:

type – The type to be checked.

Returns:

component type or null if type is not an array type.

public static Type[] getImplicitBounds(TypeVariable<?> typeVariable)

Gets an array containing the sole type of Object if TypeVariable#getBounds() returns an empty array. Otherwise, it returns the result of TypeVariable#getBounds() passed into #normalizeUpperBounds.

Parameters:

typeVariable – The subject type variable, not null.

Returns:

A non-empty array containing the bounds of the type variable, which could be Object.

Throws:

java.lang.NullPointerException – Thrown if typeVariable is null.

public static Type[] getImplicitLowerBounds(WildcardType wildcardType)

Gets an array containing a single value of null if WildcardType#getLowerBounds() returns an empty array. Otherwise, it returns the result of WildcardType#getLowerBounds().

Parameters:

wildcardType – The subject wildcard type, not null.

Returns:

A non-empty array containing the lower bounds of the wildcard type, which could be null.

Throws:

java.lang.NullPointerException – Thrown if wildcardType is null.

public static Type[] getImplicitUpperBounds(WildcardType wildcardType)

Gets an array containing the sole value of Object if WildcardType#getUpperBounds() returns an empty array. Otherwise, it returns the result of WildcardType#getUpperBounds() passed into #normalizeUpperBounds.

Parameters:

wildcardType – The subject wildcard type, not null.

Returns:

A non-empty array containing the upper bounds of the wildcard type.

Throws:

java.lang.NullPointerException – Thrown if wildcardType is null.

public static Class<?> getRawType(Type type, Type assigningType)

Gets the raw type of a Java type, given its context. Primarily for use with TypeVariables and GenericArrayTypes, or when you do not know the runtime type of type: if you know you have a Class instance, it is already raw; if you know you have a ParameterizedType, its raw type is only a method call away.

Parameters:

• type – to resolve.

• assigningType – type to be resolved against.

Returns:

The resolved Class object or null if the type could not be resolved.

public static Map<TypeVariable<?>, Type> getTypeArguments(ParameterizedType type)

Gets all the type arguments for this parameterized type including owner hierarchy arguments such as Outer<K, V>.Inner<T>.DeepInner<E> . The arguments are returned in a Map specifying the argument type for each TypeVariable.

Parameters:

type – specifies the subject parameterized type from which to harvest the parameters.

Returns:

A Map of the type arguments to their respective type variables.

public static Map<TypeVariable<?>, Type> getTypeArguments(Type type, Class<?> toClass)

Gets the type arguments of a class/interface based on a subtype. For instance, this method will determine that both of the parameters for the interface Map are Object for the subtype Properties even though the subtype does not directly implement the Map interface.

This method returns null if type is not assignable to toClass. It returns an empty map if none of the classes or interfaces in its inheritance hierarchy specify any type arguments.

A side effect of this method is that it also retrieves the type arguments for the classes and interfaces that are part of the hierarchy between type and toClass. So with the above example, this method will also determine that the type arguments for Hashtable are also both Object. In cases where the interface specified by toClass is (indirectly) implemented more than once (e.g. where toClass specifies the interface Iterable and type specifies a parameterized type that implements both Set and Collection), this method will look at the inheritance hierarchy of only one of the implementations/subclasses; the first interface encountered that isn’t a subinterface to one of the others in the type to toClass hierarchy.

Parameters:

• type – The type from which to determine the type parameters of toClass

• toClass – The class whose type parameters are to be determined based on the subtype type

Returns:

A Map of the type assignments for the type variables in each type in the inheritance hierarchy from type to toClass inclusive.

public static boolean isArrayType(Type type)

Tests whether the specified type denotes an array type.

Parameters:

type – The type to be checked.

Returns:

true if type is an array class or a GenericArrayType.

public static boolean isAssignable(Type type, Type toType)

Tests if the subject type may be implicitly cast to the target type following the Java generics rules. If both types are Class objects, the method returns the result of ClassUtils#isAssignable(Class, Class).

Parameters:

• type – The subject type to be assigned to the target type.

• toType – The target type.

Returns:

true if type is assignable to toType.

public static boolean isInstance(Object value, Type type)

Tests if the given value can be assigned to the target type following the Java generics rules.

Parameters:

• value – The value to be checked.

• type – The target type.

Returns:

true if value is an instance of type.

public static Type[] normalizeUpperBounds(Type[] bounds)

Strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).

Example, with the variable type declaration:

<K extends java.util.Collection<String> & java.util.List<String>>

since List is a subinterface of Collection, this method will return the bounds as if the declaration had been:

<K extends java.util.List<String>>

Parameters:

bounds – An array of types representing the upper bounds of either WildcardType or TypeVariable, not null.

Returns:

An array containing the values from bounds minus the redundant types.

Throws:

java.lang.NullPointerException – Thrown if bounds is null.

public static final ParameterizedType parameterize(Class<?> rawClass, Type... typeArguments)

Creates a parameterized type instance.

Parameters:

• rawClass – The raw class to create a parameterized type instance for.

• typeArguments – The types used for parameterization.

Returns:

ParameterizedType.

Throws:

java.lang.NullPointerException – Thrown if rawClass is null.

Since:

3.2

public static final ParameterizedType parameterize(Class<?> rawClass, Map<TypeVariable<?>, Type> typeVariableMap)

Creates a parameterized type instance.

Parameters:

• rawClass – The raw class to create a parameterized type instance for.

• typeVariableMap – The map used for parameterization.

Returns:

ParameterizedType.

Throws:

java.lang.NullPointerException – Thrown if either rawClass or typeVariableMap is null.

Since:

3.2

public static final ParameterizedType parameterizeWithOwner(Type owner, Class<?> rawClass, Type... typeArguments)

Creates a parameterized type instance.

Parameters:

• owner – The owning type.

• rawClass – The raw class to create a parameterized type instance for.

• typeArguments – The types used for parameterization.

Returns:

ParameterizedType.

Throws:

java.lang.NullPointerException – Thrown if rawClass is null.

Since:

3.2

public static final ParameterizedType parameterizeWithOwner(Type owner, Class<?> rawClass, Map<TypeVariable<?>, Type> typeVariableMap)

Creates a parameterized type instance.

Parameters:

• owner – The owning type.

• rawClass – The raw class to create a parameterized type instance for.

• typeVariableMap – The map used for parameterization.

Returns:

ParameterizedType.

Throws:

java.lang.NullPointerException – Thrown if either rawClass or typeVariableMap is null.

Since:

3.2

public static String toLongString(TypeVariable<?> typeVariable)

Formats a TypeVariable including its GenericDeclaration.

Parameters:

typeVariable – The type variable to create a String representation for, not null.

Returns:

String.

Throws:

java.lang.NullPointerException – Thrown if typeVariable is null.

Since:

3.2

public static String toString(Type type)

Formats a given type as a Java-esque String.

Parameters:

type – The type to create a String representation for, not null.

Returns:

String.

Throws:

java.lang.NullPointerException – Thrown if type is null.

Since:

3.2

public static boolean typesSatisfyVariables(Map<TypeVariable<?>, Type> typeVariableMap)

Determines whether or not specified types satisfy the bounds of their mapped type variables. When a type parameter extends another (such as <T, S extends T>), uses another as a type parameter (such as <T, S extends Comparable>>), or otherwise depends on another type variable to be specified, the dependencies must be included in typeVarAssigns.

Parameters:

typeVariableMap – specifies the potential types to be assigned to the type variables, not null.

Returns:

whether or not the types can be assigned to their respective type variables.

Throws:

java.lang.NullPointerException – Thrown if typeVariableMap is null.

public static Type unrollVariables(Map<TypeVariable<?>, Type> typeArguments, Type type)

Gets a type representing type with variable assignments “unrolled.”

Parameters:

• typeArguments – as from TypeUtils#getTypeArguments(Type, Class).

• type – The type to unroll variable assignments for.

Returns:

Type.

Since:

3.2

public static TypeUtils.WildcardTypeBuilder wildcardType()

Creates a new WildcardTypeBuilder.

Returns:

A new WildcardTypeBuilder.

Since:

3.2

public static <T> Typed<T> wrap(Class<T> type)

Wraps the specified Class in a Typed wrapper.

Type parameters:

<T> – generic type.

Parameters:

type – to wrap.

Returns:

Typed<T>.

Since:

3.2

public static <T> Typed<T> wrap(Type type)

Wraps the specified Type in a Typed wrapper.

Type parameters:

<T> – inferred generic type.

Parameters:

type – to wrap.

Returns:

Typed<T>.

Since:

3.2