content: /*
   * Copyright (c) 2005, 2020, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package jdkx.lang.model.element;
  
  
  import java.util.List;
  import jdkx.lang.model.type.TypeMirror;
  import jdkx.lang.model.util.*;
  
  /**
   * A visitor of the values of annotation interface 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 <code>visit<i>Xyz</i></code> 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.
   *
   * @apiNote
   * <strong>WARNING:</strong> 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.
   *
   * Such additions have already occurred in another visitor interface in
   * this package to support language features added after this API was
   * introduced.
   *
   * 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.
   *
   * <p>Methods to accommodate new language constructs are expected to
   * be added as default methods to provide strong source compatibility,
   * as done for {@link ElementVisitor#visitModule visitModule} in
   * {@code ElementVisitor}. The implementations of the default methods
   * in this interface will in turn call {@link visitUnknown
   * visitUnknown}, behavior that will be overridden in concrete
   * visitors supporting the source version with the new language
   * construct.
   *
   * <p>There are several families of classes implementing this visitor
   * interface in the {@linkplain jdkx.lang.model.util util
   * package}. The families follow a naming pattern along the lines of
   * {@code FooVisitor}<i>N</i> where <i>N</i> indicates the
   * {@linkplain jdkx.lang.model.SourceVersion source version} the
   * visitor is appropriate for.
   *
   * In particular, a {@code FooVisitor}<i>N</i> is expected to handle
   * all language constructs present in source version <i>N</i>. If
   * there are no new language constructs added in version
   * <i>N</i>&nbsp;+&nbsp;1 (or subsequent releases), {@code
   * FooVisitor}<i>N</i> may also handle that later source version; in
   * that case, the {@link
   * jdkx.annotation.processing.SupportedSourceVersion
   * SupportedSourceVersion} annotation on the {@code
   * FooVisitor}<i>N</i> class will indicate a later version.
   *
   * When visiting an annotation value representing a language construct
   * introduced <strong>after</strong> source version <i>N</i>, a {@code
   * FooVisitor}<i>N</i> will throw an {@link
   * UnknownAnnotationValueException} unless that behavior is overridden.
   *
   * <p>When choosing which member of a visitor family to subclass,
   * subclassing the most recent one increases the range of source
   * versions covered. When choosing which visitor family to subclass,
   * consider their built-in capabilities:
   *
   * <ul>
   *
   * <li>{@link AbstractAnnotationValueVisitor6
   * AbstractAnnotationValueVisitor}s: Skeletal visitor implementations.
   *
   * <li>{@link SimpleAnnotationValueVisitor6
   * SimpleAnnotationValueVisitor}s: Support default actions and a
   * default return value.
   *
   * </ul>
   *
   * @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 Ah&eacute;
   * @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 visit(av, null)}.
       *
       * @implSpec The default implementation is {@code visit(av, null)}.
       *
       * @param av the value to visit
       * @return  a visitor-specified result
       */
      default R visit(AnnotationValue av) {
          return visit(av, null);
      }
  
      /**
       * 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);
  }
  