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   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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  package openjdk.source.doctree;
  
  
  /**
   * A visitor of trees, in the style of the visitor design pattern.
   * Classes implementing this interface are used to operate
   * on a tree when the kind of tree is unknown at compile time.
   * When a visitor is passed to a tree's {@link DocTree#accept
   * accept} method, the <code>visit<i>Xyz</i></code> method most applicable
   * to that tree 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, doc comment
   * 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.
   *
   * @param <R> the return type of this visitor's methods.  Use {@link
   *            Void} for visitors that do not need to return results.
   * @param <P> the type of the additional parameter to this visitor's
   *            methods.  Use {@code Void} for visitors that do not need an
   *            additional parameter.
   *
   * @since 1.8
   */
  public interface DocTreeVisitor<R,P> {
  
      /**
       * Visits an AttributeTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitAttribute(AttributeTree node, P p);
  
      /**
       * Visits an AuthorTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitAuthor(AuthorTree node, P p);
  
      /**
       * Visits a CommentTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitComment(CommentTree node, P p);
  
      /**
       * Visits a DeprecatedTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitDeprecated(DeprecatedTree node, P p);
  
      /**
       * Visits a DocCommentTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitDocComment(DocCommentTree node, P p);
  
      /**
       * Visits a DocRootTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitDocRoot(DocRootTree node, P p);
  
      /**
       * Visits a DocTypeTree node.
       *
       * @implSpec Visits the provided {@code DocTypeTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       * @since 10
       */
      default R visitDocType(DocTypeTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits an EndElementTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitEndElement(EndElementTree node, P p);
  
      /**
       * Visits an EntityTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitEntity(EntityTree node, P p);
  
      /**
       * Visits an ErroneousTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitErroneous(ErroneousTree node, P p);
  
      /**
       * Visits a HiddenTree node.
       *
       * @implSpec Visits the provided {@code HiddenTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       *
       * @since 9
       */
      default R visitHidden(HiddenTree node, P p)  {
          return visitOther(node, p);
      }
  
      /**
       * Visits an IdentifierTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitIdentifier(IdentifierTree node, P p);
  
      /**
       * Visits an IndexTree node.
       *
       * @implSpec Visits the provided {@code IndexTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       *
       * @since 9
       */
      default R visitIndex(IndexTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits an InheritDocTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitInheritDoc(InheritDocTree node, P p);
  
      /**
       * Visits a LinkTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitLink(LinkTree node, P p);
  
      /**
       * Visits an LiteralTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitLiteral(LiteralTree node, P p);
  
      /**
       * Visits a ParamTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitParam(ParamTree node, P p);
  
      /**
       * Visits a ProvidesTree node.
       *
       * @implSpec Visits the provided {@code ProvidesTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       *
       * @since 9
       */
      default R visitProvides(ProvidesTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits a ReferenceTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitReference(ReferenceTree node, P p);
  
      /**
       * Visits a ReturnTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitReturn(ReturnTree node, P p);
  
      /**
       * Visits a SeeTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitSee(SeeTree node, P p);
  
      /**
       * Visits a SerialTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitSerial(SerialTree node, P p);
  
      /**
       * Visits a SerialDataTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitSerialData(SerialDataTree node, P p);
  
      /**
       * Visits a SerialFieldTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitSerialField(SerialFieldTree node, P p);
  
      /**
       * Visits a SinceTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitSince(SinceTree node, P p);
  
      /**
       * Visits a StartElementTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitStartElement(StartElementTree node, P p);
  
      /**
       * Visits a SummaryTree node.
       *
       * @implSpec Visits the provided {@code SummaryTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       * @since 10
       */
      default R visitSummary(SummaryTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits a SystemPropertyTree node.
       *
       * @implSpec Visits the provided {@code SystemPropertyTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       * @since 12
       */
      default R visitSystemProperty(SystemPropertyTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits a TextTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitText(TextTree node, P p);
  
      /**
       * Visits a ThrowsTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitThrows(ThrowsTree node, P p);
  
      /**
       * Visits an UnknownBlockTagTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitUnknownBlockTag(UnknownBlockTagTree node, P p);
  
      /**
       * Visits an UnknownInlineTagTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitUnknownInlineTag(UnknownInlineTagTree node, P p);
  
      /**
       * Visits a UsesTree node.
       *
       * @implSpec Visits a {@code UsesTree} node
       * by calling {@code visitOther(node, p)}.
       *
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       *
       * @since 9
       */
      default R visitUses(UsesTree node, P p) {
          return visitOther(node, p);
      }
  
      /**
       * Visits a ValueTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitValue(ValueTree node, P p);
  
      /**
       * Visits a VersionTree node.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitVersion(VersionTree node, P p);
  
      /**
       * Visits an unknown type of DocTree node.
       * This can occur if the set of tags evolves and new kinds
       * of nodes are added to the {@code DocTree} hierarchy.
       * @param node the node being visited
       * @param p a parameter value
       * @return a result value
       */
      R visitOther(DocTree node, P p);
  }
  