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
029 import javax.lang.model.element.*;
030 import javax.annotation.processing.SupportedSourceVersion;
031 import javax.lang.model.element.*;
032 import static javax.lang.model.element.ElementKind.*;
033 import static javax.lang.model.SourceVersion.*;
034 import javax.lang.model.SourceVersion;
035
036
037 /**
038 * A skeletal visitor of program elements with default behavior
039 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
040 * source version.
041 *
042 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
043 * implemented by this class may have methods added to it in the
044 * future to accommodate new, currently unknown, language structures
045 * added to future versions of the Java™ programming language.
046 * Therefore, methods whose names begin with {@code "visit"} may be
047 * added to this class in the future; to avoid incompatibilities,
048 * classes which extend this class should not declare any instance
049 * methods with names beginning with {@code "visit"}.
050 *
051 * <p>When such a new visit method is added, the default
052 * implementation in this class will be to call the {@link
053 * #visitUnknown visitUnknown} method. A new abstract element visitor
054 * class will also be introduced to correspond to the new language
055 * level; this visitor will have different default behavior for the
056 * visit method in question. When the new visitor is introduced, all
057 * or portions of this visitor may be deprecated.
058 *
059 * @param <R> the return type of this visitor's methods. Use {@link
060 * Void} for visitors that do not need to return results.
061 * @param <P> the type of the additional parameter to this visitor's
062 * methods. Use {@code Void} for visitors that do not need an
063 * additional parameter.
064 *
065 * @author Joseph D. Darcy
066 * @author Scott Seligman
067 * @author Peter von der Ahé
068 * @since 1.6
069 */
070 @SupportedSourceVersion(RELEASE_6)
071 public abstract class AbstractElementVisitor6<R, P> implements ElementVisitor<R, P> {
072 /**
073 * Constructor for concrete subclasses to call.
074 */
075 protected AbstractElementVisitor6(){}
076
077 /**
078 * Visits any program element as if by passing itself to that
079 * element's {@link Element#accept accept} method. The invocation
080 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
081 * p)}.
082 *
083 * @param e the element to visit
084 * @param p a visitor-specified parameter
085 * @return a visitor-specified result
086 */
087 public final R visit(Element e, P p) {
088 return e.accept(this, p);
089 }
090
091 /**
092 * Visits any program element as if by passing itself to that
093 * element's {@link Element#accept accept} method and passing
094 * {@code null} for the additional parameter. The invocation
095 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
096 * null)}.
097 *
098 * @param e the element to visit
099 * @return a visitor-specified result
100 */
101 public final R visit(Element e) {
102 return e.accept(this, null);
103 }
104
105 /**
106 * {@inheritDoc}
107 *
108 * <p> The default implementation of this method in
109 * {@code AbstractElementVisitor6} will always throw
110 * {@code UnknownElementException}.
111 * This behavior is not required of a subclass.
112 *
113 * @param e the element to visit
114 * @param p a visitor-specified parameter
115 * @return a visitor-specified result
116 * @throws UnknownElementException
117 * a visitor implementation may optionally throw this exception
118 */
119 public R visitUnknown(Element e, P p) {
120 throw new UnknownElementException(e, p);
121 }
122 }