1 /*

     2  * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package javax.lang.model.util;

    27 

    28 import javax.lang.model.element.*;

    29 import javax.annotation.processing.SupportedSourceVersion;

    30 import javax.lang.model.SourceVersion;

    31 import static javax.lang.model.SourceVersion.*;

    32 

    33 

    34 /**

    35  * A scanning visitor of program elements with default behavior

    36  * appropriate for the {@link SourceVersion#RELEASE_9 RELEASE_9}

    37  * source version.  The <tt>visit<i>XYZ</i></tt> methods in this

    38  * class scan their component elements by calling {@code scan} on

    39  * their {@linkplain Element#getEnclosedElements enclosed elements},

    40  * {@linkplain ExecutableElement#getParameters parameters}, etc., as

    41  * indicated in the individual method specifications.  A subclass can

    42  * control the order elements are visited by overriding the

    43  * <tt>visit<i>XYZ</i></tt> methods.  Note that clients of a scanner

    44  * may get the desired behavior be invoking {@code v.scan(e, p)} rather

    45  * than {@code v.visit(e, p)} on the root objects of interest.

    46  *

    47  * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the

    48  * new method can cause the enclosed elements to be scanned in the

    49  * default way by calling <tt>super.visit<i>XYZ</i></tt>.  In this

    50  * fashion, the concrete visitor can control the ordering of traversal

    51  * over the component elements with respect to the additional

    52  * processing; for example, consistently calling

    53  * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden

    54  * methods will yield a preorder traversal, etc.  If the component

    55  * elements should be traversed in some other order, instead of

    56  * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method

    57  * should call {@code scan} with the elements in the desired order.

    58  *

    59  * <p> Methods in this class may be overridden subject to their

    60  * general contract.  Note that annotating methods in concrete

    61  * subclasses with {@link java.lang.Override @Override} will help

    62  * ensure that methods are overridden as intended.

    63  *

    64  * <p> <b>WARNING:</b> The {@code ElementVisitor} interface

    65  * implemented by this class may have methods added to it in the

    66  * future to accommodate new, currently unknown, language structures

    67  * added to future versions of the Java™ programming language.

    68  * Therefore, methods whose names begin with {@code "visit"} may be

    69  * added to this class in the future; to avoid incompatibilities,

    70  * classes which extend this class should not declare any instance

    71  * methods with names beginning with {@code "visit"}.

    72  *

    73  * <p>When such a new visit method is added, the default

    74  * implementation in this class will be to call the {@link

    75  * #visitUnknown visitUnknown} method.  A new element scanner visitor

    76  * class will also be introduced to correspond to the new language

    77  * level; this visitor will have different default behavior for the

    78  * visit method in question.  When the new visitor is introduced, all

    79  * or portions of this visitor may be deprecated.

    80  *

    81  * @param <R> the return type of this visitor's methods.  Use {@link

    82  *            Void} for visitors that do not need to return results.

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

    84  *            methods.  Use {@code Void} for visitors that do not need an

    85  *            additional parameter.

    86  *

    87  * @see ElementScanner6

    88  * @see ElementScanner7

    89  * @see ElementScanner8

    90  * @since 1.9

    91  */

    92 @SupportedSourceVersion(RELEASE_9)

    93 public class ElementScanner9<R, P> extends ElementScanner8<R, P> {

    94     /**

    95      * Constructor for concrete subclasses; uses {@code null} for the

    96      * default value.

    97      */

    98     protected ElementScanner9(){

    99         super(null);

   100     }

   101 

   102     /**

   103      * Constructor for concrete subclasses; uses the argument for the

   104      * default value.

   105      *

   106      * @param defaultValue the default value

   107      */

   108     protected ElementScanner9(R defaultValue){

   109         super(defaultValue);

   110     }

   111 }