Module java.compiler

Package javax.lang.model.util

Interface Types

public interface Types

Utility methods for operating on types.

Compatibility Note: Methods may be added to this interface in future releases of the platform.

Since:

1.6

See Also:

• ProcessingEnvironment.getTypeUtils()

Method Summary

Modifier and Type	Method	Description
Element	asElement(TypeMirror t)	Returns the element corresponding to a type.
TypeMirror	asMemberOf(DeclaredType containing, Element element)	Returns the type of an element when that element is viewed as a member of, or otherwise directly contained by, a given type.
TypeElement	boxedClass(PrimitiveType p)	Returns the class of a boxed value of the primitive type argument.
TypeMirror	capture(TypeMirror t)	Applies capture conversion to a type.
boolean	contains(TypeMirror t1, TypeMirror t2)	Tests whether one type argument contains another.
List<? extends TypeMirror>	directSupertypes(TypeMirror t)	Returns the direct supertypes of a type.
TypeMirror	erasure(TypeMirror t)	Returns the erasure of a type.
ArrayType	getArrayType(TypeMirror componentType)	Returns an array type with the specified component type.
DeclaredType	getDeclaredType(TypeElement typeElem, TypeMirror... typeArgs)	Returns the type corresponding to a type element and actual type arguments.
DeclaredType	getDeclaredType(DeclaredType containing, TypeElement typeElem, TypeMirror... typeArgs)	Returns the type corresponding to a type element and actual type arguments, given a containing type of which it is a member.
NoType	getNoType(TypeKind kind)	Returns a pseudo-type used where no actual type is appropriate.
NullType	getNullType()	Returns the null type.
PrimitiveType	getPrimitiveType(TypeKind kind)	Returns a primitive type.
WildcardType	getWildcardType(TypeMirror extendsBound, TypeMirror superBound)	Returns a new wildcard type.
boolean	isAssignable(TypeMirror t1, TypeMirror t2)	Tests whether one type is assignable to another.
boolean	isSameType(TypeMirror t1, TypeMirror t2)	Tests whether two TypeMirror objects represent the same type.
boolean	isSubsignature(ExecutableType m1, ExecutableType m2)	Tests whether the signature of one method is a subsignature of another.
boolean	isSubtype(TypeMirror t1, TypeMirror t2)	Tests whether one type is a subtype of another.
PrimitiveType	unboxedType(TypeMirror t)	Returns the type (a primitive type) of unboxed values of a given type.

Method Details

asElement

Element asElement(TypeMirror t)

Returns the element corresponding to a type. The type may be one of:

• a DeclaredType
• a TypeVariable
• a pseudo-type for a package or module

The method returns null if the type is not one with a corresponding element. Types without corresponding elements include:

• primitive types
• executable types
• "none" pseudo-types
• null types
• void
• wildcard type argument

Parameters:

t - the type to map to an element

Returns:

the element corresponding to the given type

isSameType

boolean isSameType(TypeMirror t1,
 TypeMirror t2)

Tests whether two TypeMirror objects represent the same type.

Caveat: if either of the arguments to this method represents a wildcard, this method will return false. As a consequence, a wildcard is not the same type as itself. This might be surprising at first, but makes sense once you consider that an example like this must be rejected by the compiler:

   List<?> list = new ArrayList<Object>();
   list.add(list.get(0));
 

Since annotations are only meta-data associated with a type, the set of annotations on either argument is not taken into account when computing whether or not two TypeMirror objects are the same type. In particular, two TypeMirror objects can have different annotations and still be considered the same.

Parameters:

t1 - the first type

t2 - the second type

Returns:

true if and only if the two types are the same

isSubtype

boolean isSubtype(TypeMirror t1,
 TypeMirror t2)

Tests whether one type is a subtype of another. Any type is considered to be a subtype of itself.

Parameters:

t1 - the first type

t2 - the second type

Returns:

true if and only if the first type is a subtype of the second

Throws:

IllegalArgumentException - if given a type for an executable, package, or module

See Java Language Specification:

4.10 Subtyping

isAssignable

boolean isAssignable(TypeMirror t1,
 TypeMirror t2)

Tests whether one type is assignable to another.

Parameters:

t1 - the first type

t2 - the second type

Returns:

true if and only if the first type is assignable to the second

Throws:

IllegalArgumentException - if given a type for an executable, package, or module

See Java Language Specification:

5.2 Assignment Contexts

contains

boolean contains(TypeMirror t1,
 TypeMirror t2)

Tests whether one type argument contains another.

Parameters:

t1 - the first type

t2 - the second type

Returns:

true if and only if the first type contains the second

Throws:

IllegalArgumentException - if given a type for an executable, package, or module

See Java Language Specification:

4.5.1 Type Arguments of Parameterized Types

isSubsignature

boolean isSubsignature(ExecutableType m1,
 ExecutableType m2)

Tests whether the signature of one method is a subsignature of another.

Parameters:

m1 - the first method

m2 - the second method

Returns:

true if and only if the first signature is a subsignature of the second

See Java Language Specification:

8.4.2 Method Signature

directSupertypes

List<? extends TypeMirror> directSupertypes(TypeMirror t)

Returns the direct supertypes of a type. The interface types, if any, will appear last in the list. For an interface type with no direct super-interfaces, a type mirror representing java.lang.Object is returned. The type java.lang.Object has no direct supertype (JLS 8.1.4, 8.1.5) so an empty list is returned for the direct supertypes of a type mirror representing java.lang.Object.

Parameters:

t - the type being examined

Returns:

the direct supertypes, or an empty list if none

Throws:

IllegalArgumentException - if given a type for an executable, package, or module

See Java Language Specification:

4.10 Subtyping

erasure

TypeMirror erasure(TypeMirror t)

Returns the erasure of a type.

Parameters:

t - the type to be erased

Returns:

the erasure of a type

Throws:

IllegalArgumentException - if given a type for a package or module

See Java Language Specification:

4.6 Type Erasure

boxedClass

TypeElement boxedClass(PrimitiveType p)

Returns the class of a boxed value of the primitive type argument. That is, boxing conversion is applied.

Parameters:

p - the primitive type to be converted

Returns:

the class of a boxed value of the primitive type argument

See Java Language Specification:

5.1.7 Boxing Conversion

unboxedType

PrimitiveType unboxedType(TypeMirror t)

Returns the type (a primitive type) of unboxed values of a given type. That is, unboxing conversion is applied.

Parameters:

t - the type to be unboxed

Returns:

the type of an unboxed value of type t

Throws:

IllegalArgumentException - if the given type has no unboxing conversion

See Java Language Specification:

5.1.8 Unboxing Conversion

capture

TypeMirror capture(TypeMirror t)

Applies capture conversion to a type.

Parameters:

t - the type to be converted

Returns:

the result of applying capture conversion

Throws:

IllegalArgumentException - if given a type for an executable, package, or module

See Java Language Specification:

5.1.10 Capture Conversion

getPrimitiveType

PrimitiveType getPrimitiveType(TypeKind kind)

Returns a primitive type.

Parameters:

kind - the kind of primitive type to return

Returns:

a primitive type

Throws:

IllegalArgumentException - if kind is not a primitive kind

getNullType

NullType getNullType()

Returns the null type. This is the type of null.

Returns:

the null type

getNoType

NoType getNoType(TypeKind kind)

Returns a pseudo-type used where no actual type is appropriate. The kind of type to return may be either VOID or NONE.

To get the pseudo-type corresponding to a package or module, call asType() on the element modeling the package or module. Names can be converted to elements for packages or modules using Elements.getPackageElement(CharSequence) or Elements.getModuleElement(CharSequence), respectively.

Parameters:

kind - the kind of type to return

Returns:

a pseudo-type of kind VOID or NONE

Throws:

IllegalArgumentException - if kind is not valid

getArrayType

ArrayType getArrayType(TypeMirror componentType)

Returns an array type with the specified component type.

Parameters:

componentType - the component type

Returns:

an array type with the specified component type

Throws:

IllegalArgumentException - if the component type is not valid for an array

getWildcardType

WildcardType getWildcardType(TypeMirror extendsBound,
 TypeMirror superBound)

Returns a new wildcard type. Either of the wildcard's bounds may be specified, or neither, but not both.

Parameters:

extendsBound - the extends (upper) bound, or null if none

superBound - the super (lower) bound, or null if none

Returns:

a new wildcard type

Throws:

IllegalArgumentException - if bounds are not valid

getDeclaredType

DeclaredType getDeclaredType(TypeElement typeElem,
 TypeMirror... typeArgs)

Returns the type corresponding to a type element and actual type arguments. Given the type element for Set and the type mirror for String, for example, this method may be used to get the parameterized type Set<String>.

The number of type arguments must either equal the number of the type element's formal type parameters, or must be zero. If zero, and if the type element is generic, then the type element's raw type is returned.

If a parameterized type is being returned, its type element must not be contained within a generic outer class. The parameterized type Outer<String>.Inner<Number>, for example, may be constructed by first using this method to get the type Outer<String>, and then invoking getDeclaredType(DeclaredType, TypeElement, TypeMirror...).

Parameters:

typeElem - the type element

typeArgs - the actual type arguments

Returns:

the type corresponding to a type element and actual type arguments

Throws:

IllegalArgumentException - if too many or too few type arguments are given, or if an inappropriate type argument or type element is provided

getDeclaredType

DeclaredType getDeclaredType(DeclaredType containing,
 TypeElement typeElem,
 TypeMirror... typeArgs)

Returns the type corresponding to a type element and actual type arguments, given a containing type of which it is a member. The parameterized type Outer<String>.Inner<Number>, for example, may be constructed by first using getDeclaredType(TypeElement, TypeMirror...) to get the type Outer<String>, and then invoking this method.

If the containing type is a parameterized type, the number of type arguments must equal the number of typeElem's formal type parameters. If it is not parameterized or if it is null, this method is equivalent to getDeclaredType(typeElem, typeArgs).

Parameters:

containing - the containing type, or null if none

typeElem - the type element

typeArgs - the actual type arguments

Returns:

the type corresponding to the type element and actual type arguments, contained within the given type

Throws:

IllegalArgumentException - if too many or too few type arguments are given, or if an inappropriate type argument, type element, or containing type is provided

asMemberOf

TypeMirror asMemberOf(DeclaredType containing,
 Element element)

Returns the type of an element when that element is viewed as a member of, or otherwise directly contained by, a given type. For example, when viewed as a member of the parameterized type Set<String>, the Set.add method is an ExecutableType whose parameter is of type String.

Parameters:

containing - the containing type

element - the element

Returns:

the type of the element as viewed from the containing type

Throws:

IllegalArgumentException - if the element is not a valid one for the given type