TypeMirror (Java SE 21 & JDK 21)
Description: declaration: module: java.compiler, package: javax.lang.model.type, interface: TypeMirror
Keywords: javax.lang.model.type.TypeMirror interface

Module java.compiler
Package javax.lang.model.type

# Interface TypeMirror

All Superinterfaces:
  `AnnotatedConstruct`

All Known Subinterfaces:
  `ArrayType`, `DeclaredType`, `ErrorType`, `ExecutableType`, `IntersectionType`, `NoType`, `NullType`, `PrimitiveType`, `ReferenceType`, `TypeVariable`, `UnionType`, `WildcardType`

public interface TypeMirror extends AnnotatedConstruct
Represents a type in the Java programming language. Types include primitive types, declared types (class and interface types), array types, type variables, and the null type. Also represented are wildcard type arguments, the signature and return types of executables, and pseudo-types corresponding to packages, modules, and the keyword `void`.

Types should be compared using the utility methods in `Types`. There is no guarantee that any particular type will always be represented by the same object.

To implement operations based on the class of an `TypeMirror` object, either use a visitor or use the result of the `getKind()` method. Using `instanceof` is not necessarily a reliable idiom for determining the effective class of an object in this modeling hierarchy since an implementation may choose to have a single object implement multiple `TypeMirror` subinterfaces.

See Java Language Specification:
  4.1 The Kinds of Types and Values
  4.2 Primitive Types and Values
  4.3 Reference Types and Values
  4.4 Type Variables
  4.5 Parameterized Types
  4.8 Raw Types
  4.9 Intersection Types
  10.1 Array Types
Since:
  1.6
See Also:
  - `Element`
  - `Types`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `<R, P> R`
  `accept(TypeVisitor<R,P> v, P p)`
  Applies a visitor to this type.
  `boolean`
  `equals(Object obj)`
  Obeys the general contract of `Object.equals`.
  `<A extends Annotation>
  A`
  `getAnnotation(Class<A> annotationType)`
  Returns this construct's annotation of the specified type if such an annotation is present, else `null`.
  `List<? extends AnnotationMirror>`
  `getAnnotationMirrors()`
  Returns the annotations that are directly present on this construct.
  `<A extends Annotation>
  A[]`
  `getAnnotationsByType(Class<A> annotationType)`
  Returns annotations that are associated with this construct.
  `TypeKind`
  `getKind()`
  Returns the `kind` of this type.
  `int`
  `hashCode()`
  Obeys the general contract of `Object.hashCode`.
  `String`
  `toString()`
  Returns an informative string representation of this type.

- ## Method Details

  - ### getKind

    TypeKind getKind()
    Returns the `kind` of this type.
    - The kind of a primitive type is one of the kinds for which `TypeKind.isPrimitive()` returns `true`.
    - The kind of a null type is `NULL`.
    - The kind of an array type is `ARRAY`.
    - The kind of a declared type is `DECLARED`.
    - The kind of an error type is `ERROR`.
    - The kind of a type variable is `TYPEVAR`.
    - The kind of a wildcard type is `WILDCARD`.
    - The kind of an executable type is `EXECUTABLE`.
    - The kind of a pseudo-type is one of `VOID`, `PACKAGE`, `MODULE`, or `NONE`.
    - The kind of a union type is `UNION`.
    - The kind of an intersection type is `INTERSECTION`.
    Returns:
      the `kind` of this type

  - ### equals

    boolean equals(Object obj)
    Obeys the general contract of `Object.equals`. This method does not, however, indicate whether two types represent the same type. Semantic comparisons of type equality should instead use `Types.isSameType(TypeMirror, TypeMirror)`. The results of `t1.equals(t2)` and `Types.isSameType(t1, t2)` may differ.
    Overrides:
      `equals` in class `Object`
    Parameters:
      `obj` - the object to be compared with this type
    Returns:
      `true` if the specified object is equal to this one
    See Also:
      - `Object.hashCode()`
      - `HashMap`

  - ### hashCode

    int hashCode()
    Obeys the general contract of `Object.hashCode`.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      a hash code value for this object.
    See Also:
      - `equals(java.lang.Object)`

  - ### toString

    String toString()
    Returns an informative string representation of this type. If possible, the string should be of a form suitable for representing this type in source code. Any names embedded in the result are qualified if possible.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string representation of this type

  - ### getAnnotationMirrors

    List<? extends AnnotationMirror> getAnnotationMirrors()
    Returns the annotations that are directly present on this construct.

    Note that any annotations returned by this method are type annotations.

    Specified by:
      `getAnnotationMirrors` in interface `AnnotatedConstruct`
    Returns:
      the annotations directly present on this construct; an empty list if there are none
    Since:
      1.8

  - ### getAnnotation

    <A extends Annotation> A getAnnotation(Class<A> annotationType)
    Returns this construct's annotation of the specified type if such an annotation is present, else `null`.

    The annotation returned by this method could contain an element whose value is of type `Class`. This value cannot be returned directly: information necessary to locate and load a class (such as the class loader to use) is not available, and the class might not be loadable at all. Attempting to read a `Class` object by invoking the relevant method on the returned annotation will result in a `MirroredTypeException`, from which the corresponding `TypeMirror` may be extracted. Similarly, attempting to read a `Class[]`-valued element will result in a `MirroredTypesException`.

    > Note: This method is unlike others in this and related interfaces. It operates on runtime reflective information — representations of annotation interfaces currently loaded into the VM — rather than on the representations defined by and used throughout these interfaces. Consequently, calling methods on the returned annotation object can throw many of the exceptions that can be thrown when calling methods on an annotation object returned by core reflection. This method is intended for callers that are written to operate on a known, fixed set of annotation interfaces.

    Note that any annotation returned by this method is a type annotation.

    Specified by:
      `getAnnotation` in interface `AnnotatedConstruct`
    Type Parameters:
      `A` - the annotation interface
    Parameters:
      `annotationType` - the `Class` object corresponding to the annotation interface
    Returns:
      this construct's annotation of the specified type if such an annotation is present, else `null`
    Since:
      1.8
    See Also:
      - `AnnotatedConstruct.getAnnotationMirrors()`
      - `AnnotatedElement.getAnnotation(java.lang.Class<T>)`
      - `EnumConstantNotPresentException`
      - `AnnotationTypeMismatchException`
      - `IncompleteAnnotationException`
      - `MirroredTypeException`
      - `MirroredTypesException`

  - ### getAnnotationsByType

    <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationType)
    Returns annotations that are associated with this construct. If there are no annotations associated with this construct, the return value is an array of length 0. The order of annotations which are directly or indirectly present on a construct C is computed as if indirectly present annotations on C are directly present on C in place of their container annotation, in the order in which they appear in the value element of the container annotation. The difference between this method and `AnnotatedConstruct.getAnnotation(Class)` is that this method detects if its argument is a repeatable annotation interface, and if so, attempts to find one or more annotations of that type by "looking through" a container annotation.

    The annotations returned by this method could contain an element whose value is of type `Class`. This value cannot be returned directly: information necessary to locate and load a class (such as the class loader to use) is not available, and the class might not be loadable at all. Attempting to read a `Class` object by invoking the relevant method on the returned annotation will result in a `MirroredTypeException`, from which the corresponding `TypeMirror` may be extracted. Similarly, attempting to read a `Class[]`-valued element will result in a `MirroredTypesException`.

    > Note: This method is unlike others in this and related interfaces. It operates on runtime reflective information — representations of annotation interfaces currently loaded into the VM — rather than on the representations defined by and used throughout these interfaces. Consequently, calling methods on the returned annotation object can throw many of the exceptions that can be thrown when calling methods on an annotation object returned by core reflection. This method is intended for callers that are written to operate on a known, fixed set of annotation interfaces.

    Note that any annotations returned by this method are type annotations.

    Specified by:
      `getAnnotationsByType` in interface `AnnotatedConstruct`
    Type Parameters:
      `A` - the annotation interface
    Parameters:
      `annotationType` - the `Class` object corresponding to the annotation interface
    Returns:
      this construct's annotations for the specified annotation type if present on this construct, else an empty array
    Since:
      1.8
    See Also:
      - `AnnotatedConstruct.getAnnotationMirrors()`
      - `AnnotatedConstruct.getAnnotation(Class)`
      - `AnnotatedElement.getAnnotationsByType(Class)`
      - `EnumConstantNotPresentException`
      - `AnnotationTypeMismatchException`
      - `IncompleteAnnotationException`
      - `MirroredTypeException`
      - `MirroredTypesException`

  - ### accept

    <R, P> R accept(TypeVisitor<R,P> v, P p)
    Applies a visitor to this type.
    Type Parameters:
      `R` - the return type of the visitor's methods
      `P` - the type of the additional parameter to the visitor's methods
    Parameters:
      `v` - the visitor operating on this type
      `p` - additional parameter to the visitor
    Returns:
      a visitor-specified result