1 /*
2 * Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.lang.model.util;
27
28 import javax.lang.model.element.*;
29 import javax.annotation.processing.SupportedSourceVersion;
30 import static javax.lang.model.element.ElementKind.*;
31 import javax.lang.model.SourceVersion;
32 import static javax.lang.model.SourceVersion.*;
33
34
35 /**
36 * A simple visitor of program elements with default behavior
37 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
38 * source version.
39 *
40 * Visit methods corresponding to {@code RELEASE_6} language
41 * constructs call {@link #defaultAction}, passing their arguments to
42 * {@code defaultAction}'s corresponding parameters.
43 *
44 * <p> Methods in this class may be overridden subject to their
45 * general contract. Note that annotating methods in concrete
46 * subclasses with {@link java.lang.Override @Override} will help
47 * ensure that methods are overridden as intended.
48 *
49 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
50 * implemented by this class may have methods added to it in the
51 * future to accommodate new, currently unknown, language structures
52 * added to future versions of the Java™ programming language.
53 * Therefore, methods whose names begin with {@code "visit"} may be
54 * added to this class in the future; to avoid incompatibilities,
55 * classes which extend this class should not declare any instance
56 * methods with names beginning with {@code "visit"}.
57 *
58 * <p>When such a new visit method is added, the default
59 * implementation in this class will be to call the {@link
60 * #visitUnknown visitUnknown} method. A new simple element visitor
61 * class will also be introduced to correspond to the new language
62 * level; this visitor will have different default behavior for the
63 * visit method in question. When the new visitor is introduced, all
64 * or portions of this visitor may be deprecated.
65 *
66 * @param <R> the return type of this visitor's methods. Use {@code Void}
67 * for visitors that do not need to return results.
68 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
69 * for visitors that do not need an additional parameter.
70 *
71 * @author Joseph D. Darcy
72 * @author Scott Seligman
73 * @author Peter von der Ahé
74 * @since 1.6
75 */
76 @SupportedSourceVersion(RELEASE_6)
77 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
78 /**
79 * Default value to be returned; {@link #defaultAction
80 * defaultAction} returns this value unless the method is
81 * overridden.
82 */
83 protected final R DEFAULT_VALUE;
84
85 /**
86 * Constructor for concrete subclasses; uses {@code null} for the
87 * default value.
88 */
89 protected SimpleElementVisitor6(){
90 DEFAULT_VALUE = null;
91 }
92
93 /**
94 * Constructor for concrete subclasses; uses the argument for the
95 * default value.
96 *
97 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
98 */
99 protected SimpleElementVisitor6(R defaultValue){
100 DEFAULT_VALUE = defaultValue;
101 }
102 /**
103 * The default action for visit methods. The implementation in
104 * this class just returns {@link #DEFAULT_VALUE}; subclasses will
105 * commonly override this method.
106 *
107 * @param e the element to process
108 * @param p a visitor-specified parameter
109 * @return {@code DEFAULT_VALUE} unless overridden
110 */
111 protected R defaultAction(Element e, P p) {
112 return DEFAULT_VALUE;
113 }
114
115 /**
116 * {@inheritDoc} This implementation calls {@code defaultAction}.
117 *
118 * @param e {@inheritDoc}
119 * @param p {@inheritDoc}
120 * @return the result of {@code defaultAction}
121 */
122 public R visitPackage(PackageElement e, P p) {
123 return defaultAction(e, p);
124 }
125
126 /**
127 * {@inheritDoc} This implementation calls {@code defaultAction}.
128 *
129 * @param e {@inheritDoc}
130 * @param p {@inheritDoc}
131 * @return the result of {@code defaultAction}
132 */
133 public R visitType(TypeElement e, P p) {
134 return defaultAction(e, p);
135 }
136
137 /**
138 * {@inheritDoc} This implementation calls {@code defaultAction}.
139 *
140 * @param e {@inheritDoc}
141 * @param p {@inheritDoc}
142 * @return the result of {@code defaultAction}
143 */
144 public R visitVariable(VariableElement e, P p) {
145 return defaultAction(e, p);
146 }
147
148 /**
149 * {@inheritDoc} This implementation calls {@code defaultAction}.
150 *
151 * @param e {@inheritDoc}
152 * @param p {@inheritDoc}
153 * @return the result of {@code defaultAction}
154 */
155 public R visitExecutable(ExecutableElement e, P p) {
156 return defaultAction(e, p);
157 }
158
159 /**
160 * {@inheritDoc} This implementation calls {@code defaultAction}.
161 *
162 * @param e {@inheritDoc}
163 * @param p {@inheritDoc}
164 * @return the result of {@code defaultAction}
165 */
166 public R visitTypeParameter(TypeParameterElement e, P p) {
167 return defaultAction(e, p);
168 }
169 }