1 /*
2 * Copyright (c) 2005, 2011, 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 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 defaultAction}, passing their
42 * arguments to {@code defaultAction}'s corresponding parameters.
43 *
44 * For constructs introduced in {@code RELEASE_7} and later, {@code
45 * visitUnknown} is called instead.
46 *
47 * <p> Methods in this class may be overridden subject to their
48 * general contract. Note that annotating methods in concrete
49 * subclasses with {@link java.lang.Override @Override} will help
50 * ensure that methods are overridden as intended.
51 *
52 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
53 * implemented by this class may have methods added to it in the
54 * future to accommodate new, currently unknown, language structures
55 * added to future versions of the Java™ programming language.
56 * Therefore, methods whose names begin with {@code "visit"} may be
57 * added to this class in the future; to avoid incompatibilities,
58 * classes which extend this class should not declare any instance
59 * methods with names beginning with {@code "visit"}.
60 *
61 * <p>When such a new visit method is added, the default
62 * implementation in this class will be to call the {@link
63 * #visitUnknown visitUnknown} method. A new simple element visitor
64 * class will also be introduced to correspond to the new language
65 * level; this visitor will have different default behavior for the
66 * visit method in question. When the new visitor is introduced, all
67 * or portions of this visitor may be deprecated.
68 *
69 * @param <R> the return type of this visitor's methods. Use {@code Void}
70 * for visitors that do not need to return results.
71 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
72 * for visitors that do not need an additional parameter.
73 *
74 * @author Joseph D. Darcy
75 * @author Scott Seligman
76 * @author Peter von der Ahé
77 *
78 * @see SimpleElementVisitor7
79 * @since 1.6
80 */
81 @SupportedSourceVersion(RELEASE_6)
82 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
83 /**
84 * Default value to be returned; {@link #defaultAction
85 * defaultAction} returns this value unless the method is
86 * overridden.
87 */
88 protected final R DEFAULT_VALUE;
89
90 /**
91 * Constructor for concrete subclasses; uses {@code null} for the
92 * default value.
93 */
94 protected SimpleElementVisitor6(){
95 DEFAULT_VALUE = null;
96 }
97
98 /**
99 * Constructor for concrete subclasses; uses the argument for the
100 * default value.
101 *
102 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
103 */
104 protected SimpleElementVisitor6(R defaultValue){
105 DEFAULT_VALUE = defaultValue;
106 }
107 /**
108 * The default action for visit methods. The implementation in
109 * this class just returns {@link #DEFAULT_VALUE}; subclasses will
110 * commonly override this method.
111 *
112 * @param e the element to process
113 * @param p a visitor-specified parameter
114 * @return {@code DEFAULT_VALUE} unless overridden
115 */
116 protected R defaultAction(Element e, P p) {
117 return DEFAULT_VALUE;
118 }
119
120 /**
121 * {@inheritDoc} This implementation calls {@code defaultAction}.
122 *
123 * @param e {@inheritDoc}
124 * @param p {@inheritDoc}
125 * @return the result of {@code defaultAction}
126 */
127 public R visitPackage(PackageElement e, P p) {
128 return defaultAction(e, p);
129 }
130
131 /**
132 * {@inheritDoc} This implementation calls {@code defaultAction}.
133 *
134 * @param e {@inheritDoc}
135 * @param p {@inheritDoc}
136 * @return the result of {@code defaultAction}
137 */
138 public R visitType(TypeElement e, P p) {
139 return defaultAction(e, p);
140 }
141
142 /**
143 * {@inheritDoc}
144 *
145 * This implementation calls {@code defaultAction}, unless the
146 * element is a {@code RESOURCE_VARIABLE} in which case {@code
147 * visitUnknown} is called.
148 *
149 * @param e {@inheritDoc}
150 * @param p {@inheritDoc}
151 * @return the result of {@code defaultAction} or {@code visitUnknown}
152 */
153 public R visitVariable(VariableElement e, P p) {
154 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
155 return defaultAction(e, p);
156 else
157 return visitUnknown(e, p);
158 }
159
160 /**
161 * {@inheritDoc} This implementation calls {@code defaultAction}.
162 *
163 * @param e {@inheritDoc}
164 * @param p {@inheritDoc}
165 * @return the result of {@code defaultAction}
166 */
167 public R visitExecutable(ExecutableElement e, P p) {
168 return defaultAction(e, p);
169 }
170
171 /**
172 * {@inheritDoc} This implementation calls {@code defaultAction}.
173 *
174 * @param e {@inheritDoc}
175 * @param p {@inheritDoc}
176 * @return the result of {@code defaultAction}
177 */
178 public R visitTypeParameter(TypeParameterElement e, P p) {
179 return defaultAction(e, p);
180 }
181 }