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package javax.lang.model.element;

import java.util.List;

import javax.lang.model.type.TypeMirror;

/**

 * 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,

 * {@code boolean} values versus {@code 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 {@link AnnotationValue#accept accept} method,

 * the <tt>visit<i>XYZ</i></tt> method applicable to that value is

 * invoked.

 *

 * <p> Classes implementing this interface may or may not throw a

 * {@code NullPointerException} if the additional parameter {@code p}

 * is {@code null}; see documentation of the implementing class for

 * details.

 *

 * <p> <b>WARNING:</b> 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.

 *

 * @param <R> the return type of this visitor's methods

 * @param <P> the type of the additional parameter to this visitor's methods.

 * @author Joseph D. Darcy

 * @author Scott Seligman

 * @author Peter von der Ahé

 * @since 1.6

 */

public interface AnnotationValueVisitor<R, P> {

    /**

     * Visits an annotation value.

     * @param av the value to visit

     * @param p a visitor-specified parameter

     * @return  a visitor-specified result

     */

    R visit(AnnotationValue av, P p);

    /**

     * A convenience method equivalent to {@code v.visit(av, null)}.

     * @param av the value to visit

     * @return  a visitor-specified result

     */

    R visit(AnnotationValue av);

    /**

     * Visits a {@code boolean} value in an annotation.

     * @param b the value being visited

     * @param p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitBoolean(boolean b, P p);

    /**

     * Visits a {@code byte} value in an annotation.

     * @param  b the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitByte(byte b, P p);

    /**

     * Visits a {@code char} value in an annotation.

     * @param  c the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitChar(char c, P p);

    /**

     * Visits a {@code double} value in an annotation.

     * @param  d the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitDouble(double d, P p);

    /**

     * Visits a {@code float} value in an annotation.

     * @param  f the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitFloat(float f, P p);

    /**

     * Visits an {@code int} value in an annotation.

     * @param  i the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitInt(int i, P p);

    /**

     * Visits a {@code long} value in an annotation.

     * @param  i the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitLong(long i, P p);

    /**

     * Visits a {@code short} value in an annotation.

     * @param  s the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitShort(short s, P p);

    /**

     * Visits a string value in an annotation.

     * @param  s the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitString(String s, P p);

    /**

     * Visits a type value in an annotation.

     * @param  t the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitType(TypeMirror t, P p);

    /**

     * Visits an {@code enum} value in an annotation.

     * @param  c the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitEnumConstant(VariableElement c, P p);

    /**

     * Visits an annotation value in an annotation.

     * @param  a the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitAnnotation(AnnotationMirror a, P p);

    /**

     * Visits an array value in an annotation.

     * @param  vals the value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     */

    R visitArray(List<? extends AnnotationValue> vals, 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.

     * @param  av the unknown value being visited

     * @param  p a visitor-specified parameter

     * @return the result of the visit

     * @throws UnknownAnnotationValueException

     *  a visitor implementation may optionally throw this exception

     */

    R visitUnknown(AnnotationValue av, P p);

}