text: /*
   * Copyright (c) 2011, 2018, 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 javax.lang.model.util;
  
  import javax.lang.model.element.*;
  import javax.annotation.processing.SupportedSourceVersion;
  import javax.lang.model.SourceVersion;
  import static javax.lang.model.SourceVersion.*;
  
  
  /**
   * A scanning visitor of program elements with default behavior
   * appropriate for source versions {@link SourceVersion#RELEASE_9
   * RELEASE_9} through {@link SourceVersion#RELEASE_11 RELEASE_11}.
   *
   * The <code>visit<i>Xyz</i></code> methods in this
   * class scan their component elements by calling {@code scan} on
   * their {@linkplain Element#getEnclosedElements enclosed elements},
   * {@linkplain ExecutableElement#getParameters parameters}, etc., as
   * indicated in the individual method specifications.  A subclass can
   * control the order elements are visited by overriding the
   * <code>visit<i>Xyz</i></code> methods.  Note that clients of a scanner
   * may get the desired behavior be invoking {@code v.scan(e, p)} rather
   * than {@code v.visit(e, p)} on the root objects of interest.
   *
   * <p>When a subclass overrides a <code>visit<i>Xyz</i></code> method, the
   * new method can cause the enclosed elements to be scanned in the
   * default way by calling <code>super.visit<i>Xyz</i></code>.  In this
   * fashion, the concrete visitor can control the ordering of traversal
   * over the component elements with respect to the additional
   * processing; for example, consistently calling
   * <code>super.visit<i>Xyz</i></code> at the start of the overridden
   * methods will yield a preorder traversal, etc.  If the component
   * elements should be traversed in some other order, instead of
   * calling <code>super.visit<i>Xyz</i></code>, an overriding visit method
   * should call {@code scan} with the elements in the desired order.
   *
   * <p> Methods in this class may be overridden subject to their
   * general contract.  Note that annotating methods in concrete
   * subclasses with {@link java.lang.Override @Override} will help
   * ensure that methods are overridden as intended.
   *
   * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
   * implemented by this class may have methods added to it in the
   * future to accommodate new, currently unknown, language structures
   * added to future versions of the Java&trade; programming language.
   * Therefore, methods whose names begin with {@code "visit"} may be
   * added to this class in the future; to avoid incompatibilities,
   * classes which extend this class should not declare any instance
   * methods with names beginning with {@code "visit"}.
   *
   * <p>When such a new visit method is added, the default
   * implementation in this class will be to call the {@link
   * #visitUnknown visitUnknown} method.  A new element scanner visitor
   * class will also be introduced to correspond to the new language
   * level; this visitor will have different default behavior for the
   * visit method in question.  When the new visitor is introduced, all
   * or portions of this visitor may be deprecated.
   *
   * @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.
   *
   * @see ElementScanner6
   * @see ElementScanner7
   * @see ElementScanner8
   * @since 9
   * @spec JPMS
   */
  @SupportedSourceVersion(RELEASE_11)
  public class ElementScanner9<R, P> extends ElementScanner8<R, P> {
      /**
       * Constructor for concrete subclasses; uses {@code null} for the
       * default value.
       */
      protected ElementScanner9(){
          super(null);
      }
  
      /**
       * Constructor for concrete subclasses; uses the argument for the
       * default value.
       *
       * @param defaultValue the default value
       */
      protected ElementScanner9(R defaultValue){
          super(defaultValue);
      }
  
      /**
       * {@inheritDoc}
       *
       * @implSpec This implementation scans the enclosed elements.
       *
       * @param e the element to visit
       * @param p a visitor-specified parameter
       * @return  the result of the scan
       */
      @Override
      public R visitModule(ModuleElement e, P p) {
          return scan(e.getEnclosedElements(), p); // TODO: Hmmm, this might not be right
      }
  }
  