001 /*
002 * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package javax.lang.model.util;
027
028 import javax.lang.model.element.*;
029 import javax.annotation.processing.SupportedSourceVersion;
030 import javax.lang.model.element.*;
031 import static javax.lang.model.element.ElementKind.*;
032 import static javax.lang.model.SourceVersion.*;
033 import javax.lang.model.SourceVersion;
034
035 /**
036 * A skeletal visitor of program elements with default behavior
037 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
038 * source version.
039 *
040 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
041 * implemented by this class may have methods added to it in the
042 * future to accommodate new, currently unknown, language structures
043 * added to future versions of the Java™ programming language.
044 * Therefore, methods whose names begin with {@code "visit"} may be
045 * added to this class in the future; to avoid incompatibilities,
046 * classes which extend this class should not declare any instance
047 * methods with names beginning with {@code "visit"}.
048 *
049 * <p>When such a new visit method is added, the default
050 * implementation in this class will be to call the {@link
051 * #visitUnknown visitUnknown} method. A new abstract element visitor
052 * class will also be introduced to correspond to the new language
053 * level; this visitor will have different default behavior for the
054 * visit method in question. When the new visitor is introduced, all
055 * or portions of this visitor may be deprecated.
056 *
057 * @param <R> the return type of this visitor's methods. Use {@link
058 * Void} for visitors that do not need to return results.
059 * @param <P> the type of the additional parameter to this visitor's
060 * methods. Use {@code Void} for visitors that do not need an
061 * additional parameter.
062 *
063 * @author Joseph D. Darcy
064 * @author Scott Seligman
065 * @author Peter von der Ahé
066 * @version 1.10 07/05/05
067 * @since 1.6
068 */
069 @SupportedSourceVersion(RELEASE_6)
070 public abstract class AbstractElementVisitor6<R, P> implements
071 ElementVisitor<R, P> {
072 /**
073 * Constructor for concrete subclasses to call.
074 */
075 protected AbstractElementVisitor6() {
076 }
077
078 /**
079 * Visits any program element as if by passing itself to that
080 * element's {@link Element#accept accept} method. The invocation
081 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
082 * p)}.
083 *
084 * @param e the element to visit
085 * @param p a visitor-specified parameter
086 * @return a visitor-specified result
087 */
088 public final R visit(Element e, P p) {
089 return e.accept(this , p);
090 }
091
092 /**
093 * Visits any program element as if by passing itself to that
094 * element's {@link Element#accept accept} method and passing
095 * {@code null} for the additional parameter. The invocation
096 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
097 * null)}.
098 *
099 * @param e the element to visit
100 * @return a visitor-specified result
101 */
102 public final R visit(Element e) {
103 return e.accept(this , null);
104 }
105
106 /**
107 * {@inheritDoc}
108 *
109 * <p> The default implementation of this method in
110 * {@code AbstractElementVisitor6} will always throw
111 * {@code UnknownElementException}.
112 * This behavior is not required of a subclass.
113 *
114 * @param e the element to visit
115 * @param p a visitor-specified parameter
116 * @return a visitor-specified result
117 * @throws UnknownElementException
118 * a visitor implementation may optionally throw this exception
119 */
120 public R visitUnknown(Element e, P p) {
121 throw new UnknownElementException(e, p);
122 }
123 }
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