Interface Types

public interface Types
Utility methods for operating on types. Most methods operate on primitive types, reference types (including array types and the null type), intersection types, and the pseudo-type 'void'. Executable types and the pseudo-types for packages and modules are generally out of scope for these methods. One or more out of scope arguments will typically result in a method throwing an IllegalArgumentException.

Where a method returns a type mirror or a collection of type mirrors, any type mirrors represent types with no type annotations, unless otherwise indicated.

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

Since:
1.6
See Also:

  • Method Details

    • asElement

      Element asElement(TypeMirror t)
      Returns the element corresponding to a type. The type may be one of: The method returns null if the type is not one with a corresponding element. Types without corresponding elements include:
      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. Annotations on the direct super types are preserved.
      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
      See Java Language Specification:
      4.2 Primitive Types and Values

    • getNullType

      NullType getNullType()
      Returns the null type. This is the type of null.
      Returns:
      the null type
      See Java Language Specification:
      4.1 The Kinds of Types and Values

    • 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. Annotations on the component type are preserved.
      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, including executable, package, module, and wildcard types
      See Java Language Specification:
      10.1 Array Types

    • 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. Annotations on the bounds are preserved.
      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
      See Java Language Specification:
      4.5.1 Type Arguments of Parameterized Types

    • 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>. Annotations on the type arguments are preserved.

      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. Annotations on the type arguments are preserved.

      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

    • stripAnnotations

      default <T extends TypeMirror> T stripAnnotations(T t)
      Returns a type mirror equivalent to the argument, but with no annotations. If the type mirror is a composite type, such as an array type or a wildcard type, any constitute types, such as the component type of an array and the type of the bounds of a wildcard type, also have no annotations, recursively.

      For most kinds of type mirrors, the result of 

        types.isSameType(typeMirror, types.stripAnnotations(typeMirror))
      is true. The predicate is false on wildcard types for reasons discussed elsewhere.
      Implementation Requirements:
      The default implementation throws UnsupportedOperationException.
      Type Parameters:
      T - the specific type of type mirror
      Parameters:
      t - the type mirror
      Returns:
      a type mirror equivalent to the argument, but with no annotations
      Since:
      23