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

## Interface AnnotationValueVisitor<R,​P>

- Type Parameters:
    `R` - the return type of this visitor's methods
    `P` - the type of the additional parameter to this visitor's methods.
  All Known Implementing Classes:
    `AbstractAnnotationValueVisitor6`, `AbstractAnnotationValueVisitor7`, `AbstractAnnotationValueVisitor8`, `AbstractAnnotationValueVisitor9`, `SimpleAnnotationValueVisitor6`, `SimpleAnnotationValueVisitor7`, `SimpleAnnotationValueVisitor8`, `SimpleAnnotationValueVisitor9`

      public interface AnnotationValueVisitor<R,​P>

  A visitor of the values of annotation type elements, using a variant of the visitor design pattern. Unlike a standard visitor which dispatches based on the concrete type of a member of a type hierarchy, this visitor dispatches based on the type of data stored; there are no distinct subclasses for storing, for example, `boolean` values versus `int` values. Classes implementing this interface are used to operate on a value when the type of that value is unknown at compile time. When a visitor is passed to a value's `accept` method, the `visitXyz` method applicable to that value is invoked.

  Classes implementing this interface may or may not throw a `NullPointerException` if the additional parameter `p` is `null`; see documentation of the implementing class for details.

  WARNING: It is possible that methods will be added to this interface to accommodate new, currently unknown, language structures added to future versions of the Java™ programming language. Therefore, visitor classes directly implementing this interface may be source incompatible with future versions of the platform. To avoid this source incompatibility, visitor implementations are encouraged to instead extend the appropriate abstract visitor class that implements this interface. However, an API should generally use this visitor interface as the type for parameters, return type, etc. rather than one of the abstract classes.

  Note that methods to accommodate new language constructs could be added in a source compatible way if they were added as default methods. However, default methods are only available on Java SE 8 and higher releases and the `javax.lang.model.*` packages bundled in Java SE 8 were required to also be runnable on Java SE 7. Therefore, default methods were not used when extending `javax.lang.model.*` to cover Java SE 8 language features. However, default methods are used in subsequent revisions of the `javax.lang.model.*` packages that are only required to run on Java SE 8 and higher platform versions.

  Since:
    1.6

- - ### Method Summary

    Modifier and Type | Method | Description
    --- | --- | ---
    `default R` | `visit​(AnnotationValue av)` | A convenience method equivalent to `visit(av, null)`.
    `R` | `visit​(AnnotationValue av, P p)` | Visits an annotation value.
    `R` | `visitAnnotation​(AnnotationMirror a, P p)` | Visits an annotation value in an annotation.
    `R` | `visitArray​(List<? extends AnnotationValue> vals, P p)` | Visits an array value in an annotation.
    `R` | `visitBoolean​(boolean b, P p)` | Visits a `boolean` value in an annotation.
    `R` | `visitByte​(byte b, P p)` | Visits a `byte` value in an annotation.
    `R` | `visitChar​(char c, P p)` | Visits a `char` value in an annotation.
    `R` | `visitDouble​(double d, P p)` | Visits a `double` value in an annotation.
    `R` | `visitEnumConstant​(VariableElement c, P p)` | Visits an `enum` value in an annotation.
    `R` | `visitFloat​(float f, P p)` | Visits a `float` value in an annotation.
    `R` | `visitInt​(int i, P p)` | Visits an `int` value in an annotation.
    `R` | `visitLong​(long i, P p)` | Visits a `long` value in an annotation.
    `R` | `visitShort​(short s, P p)` | Visits a `short` value in an annotation.
    `R` | `visitString​(String s, P p)` | Visits a string value in an annotation.
    `R` | `visitType​(TypeMirror t, P p)` | Visits a type value in an annotation.
    `R` | `visitUnknown​(AnnotationValue av, P p)` | Visits an unknown kind of annotation value.

- - ### Method Detail

    - #### visit

          R visit​(AnnotationValue av,
                  P p)

      Visits an annotation value.
      Parameters:
        `av` - the value to visit
        `p` - a visitor-specified parameter
      Returns:
        a visitor-specified result

    - #### visit

          default R visit​(AnnotationValue av)

      A convenience method equivalent to `visit(av, null)`.
      Implementation Requirements:
        The default implementation is `visit(av, null)`.
      Parameters:
        `av` - the value to visit
      Returns:
        a visitor-specified result

    - #### visitBoolean

          R visitBoolean​(boolean b,
                         P p)

      Visits a `boolean` value in an annotation.
      Parameters:
        `b` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitByte

          R visitByte​(byte b,
                      P p)

      Visits a `byte` value in an annotation.
      Parameters:
        `b` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitChar

          R visitChar​(char c,
                      P p)

      Visits a `char` value in an annotation.
      Parameters:
        `c` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitDouble

          R visitDouble​(double d,
                        P p)

      Visits a `double` value in an annotation.
      Parameters:
        `d` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitFloat

          R visitFloat​(float f,
                       P p)

      Visits a `float` value in an annotation.
      Parameters:
        `f` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitInt

          R visitInt​(int i,
                     P p)

      Visits an `int` value in an annotation.
      Parameters:
        `i` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitLong

          R visitLong​(long i,
                      P p)

      Visits a `long` value in an annotation.
      Parameters:
        `i` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitShort

          R visitShort​(short s,
                       P p)

      Visits a `short` value in an annotation.
      Parameters:
        `s` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitString

          R visitString​(String s,
                        P p)

      Visits a string value in an annotation.
      Parameters:
        `s` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitType

          R visitType​(TypeMirror t,
                      P p)

      Visits a type value in an annotation.
      Parameters:
        `t` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitEnumConstant

          R visitEnumConstant​(VariableElement c,
                              P p)

      Visits an `enum` value in an annotation.
      Parameters:
        `c` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitAnnotation

          R visitAnnotation​(AnnotationMirror a,
                            P p)

      Visits an annotation value in an annotation.
      Parameters:
        `a` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitArray

          R visitArray​(List<? extends AnnotationValue> vals,
                       P p)

      Visits an array value in an annotation.
      Parameters:
        `vals` - the value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit

    - #### visitUnknown

          R visitUnknown​(AnnotationValue av,
                         P p)

      Visits an unknown kind of annotation value. This can occur if the language evolves and new kinds of value can be stored in an annotation.
      Parameters:
        `av` - the unknown value being visited
        `p` - a visitor-specified parameter
      Returns:
        the result of the visit
      Throws:
        `UnknownAnnotationValueException` - a visitor implementation may optionally throw this exception