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 * @see SimpleElementVisitor8
80 * @since 1.6
81 */
82 @SupportedSourceVersion(RELEASE_6)
83 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
84 /**
85 * Default value to be returned; {@link #defaultAction
86 * defaultAction} returns this value unless the method is
87 * overridden.
88 */
89 protected final R DEFAULT_VALUE;
90
91 /**
92 * Constructor for concrete subclasses; uses {@code null} for the
93 * default value.
94 */
95 protected SimpleElementVisitor6(){
96 DEFAULT_VALUE = null;
97 }
98
99 /**
100 * Constructor for concrete subclasses; uses the argument for the
101 * default value.
102 *
103 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
104 */
105 protected SimpleElementVisitor6(R defaultValue){
106 DEFAULT_VALUE = defaultValue;
107 }
108 /**
109 * The default action for visit methods. The implementation in
110 * this class just returns {@link #DEFAULT_VALUE}; subclasses will
111 * commonly override this method.
112 *
113 * @param e the element to process
114 * @param p a visitor-specified parameter
115 * @return {@code DEFAULT_VALUE} unless overridden
116 */
117 protected R defaultAction(Element e, P p) {
118 return DEFAULT_VALUE;
119 }
120
121 /**
122 * {@inheritDoc} This implementation calls {@code defaultAction}.
123 *
124 * @param e {@inheritDoc}
125 * @param p {@inheritDoc}
126 * @return the result of {@code defaultAction}
127 */
128 public R visitPackage(PackageElement e, P p) {
129 return defaultAction(e, p);
130 }
131
132 /**
133 * {@inheritDoc} This implementation calls {@code defaultAction}.
134 *
135 * @param e {@inheritDoc}
136 * @param p {@inheritDoc}
137 * @return the result of {@code defaultAction}
138 */
139 public R visitType(TypeElement e, P p) {
140 return defaultAction(e, p);
141 }
142
143 /**
144 * {@inheritDoc}
145 *
146 * This implementation calls {@code defaultAction}, unless the
147 * element is a {@code RESOURCE_VARIABLE} in which case {@code
148 * visitUnknown} is called.
149 *
150 * @param e {@inheritDoc}
151 * @param p {@inheritDoc}
152 * @return the result of {@code defaultAction} or {@code visitUnknown}
153 */
154 public R visitVariable(VariableElement e, P p) {
155 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
156 return defaultAction(e, p);
157 else
158 return visitUnknown(e, p);
159 }
160
161 /**
162 * {@inheritDoc} This implementation calls {@code defaultAction}.
163 *
164 * @param e {@inheritDoc}
165 * @param p {@inheritDoc}
166 * @return the result of {@code defaultAction}
167 */
168 public R visitExecutable(ExecutableElement e, P p) {
169 return defaultAction(e, p);
170 }
171
172 /**
173 * {@inheritDoc} This implementation calls {@code defaultAction}.
174 *
175 * @param e {@inheritDoc}
176 * @param p {@inheritDoc}
177 * @return the result of {@code defaultAction}
178 */
179 public R visitTypeParameter(TypeParameterElement e, P p) {
180 return defaultAction(e, p);
181 }
182 }