1 /*
2 * Copyright (c) 2005, 2020, 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 javax.lang.model.SourceVersion;
31 import static javax.lang.model.SourceVersion.*;
32
33
34 /**
35 * A simple visitor of program elements with default behavior
36 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
37 * source version.
38 *
39 * Visit methods corresponding to {@code RELEASE_6} language
40 * constructs call {@link #defaultAction defaultAction}, passing their
41 * arguments to {@code defaultAction}'s corresponding parameters.
42 *
43 * For constructs introduced in {@code RELEASE_7} and later, {@code
44 * visitUnknown} is called instead.
45 *
46 *
47 * @apiNote
48 * Methods in this class may be overridden subject to their general
49 * contract.
50 *
51 * <p id=note_for_subclasses><strong>WARNING:</strong> The {@code
52 * ElementVisitor} interface implemented by this class may have
53 * methods added to it in the future to accommodate new, currently
54 * unknown, language structures added to future versions of the
55 * Java™ programming language. Therefore, methods whose names
56 * begin with {@code "visit"} may be added to this class in the
57 * future; to avoid incompatibilities, classes and subclasses which
58 * extend this class should not declare any instance methods with
59 * names beginning with {@code "visit"}.</p>
60 *
61 * <p>When such a new visit method is added, the default
62 * implementation in this class will be to directly or indirectly call
63 * the {@link #visitUnknown visitUnknown} method. A new simple
64 * element visitor class will also be introduced to correspond to the
65 * new language level; this visitor will have different default
66 * behavior for the visit method in question. When a new visitor is
67 * introduced, portions of this visitor class may be deprecated,
68 * including its constructors.
69 *
70 * @param <R> the return type of this visitor's methods. Use {@code Void}
71 * for visitors that do not need to return results.
72 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
73 * for visitors that do not need an additional parameter.
74 *
75 * @author Joseph D. Darcy
76 * @author Scott Seligman
77 * @author Peter von der Ahé
78 *
79 * @see SimpleElementVisitor7
80 * @see SimpleElementVisitor8
81 * @see SimpleElementVisitor9
82 * @see SimpleElementVisitor14
83 * @since 1.6
84 */
85 @SupportedSourceVersion(RELEASE_6)
86 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
87 /**
88 * Default value to be returned; {@link #defaultAction
89 * defaultAction} returns this value unless the method is
90 * overridden.
91 */
92 protected final R DEFAULT_VALUE;
93
94 /**
95 * Constructor for concrete subclasses; uses {@code null} for the
96 * default value.
97 * @deprecated Release 6 is obsolete; update to a visitor for a newer
98 * release level.
99 */
100 @Deprecated(since="9")
101 protected SimpleElementVisitor6(){
102 DEFAULT_VALUE = null;
103 }
104
105 /**
106 * Constructor for concrete subclasses; uses the argument for the
107 * default value.
108 *
109 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
110 * @deprecated Release 6 is obsolete; update to a visitor for a newer
111 * release level.
112 */
113 @Deprecated(since="9")
114 protected SimpleElementVisitor6(R defaultValue){
115 DEFAULT_VALUE = defaultValue;
116 }
117 /**
118 * The default action for visit methods.
119 *
120 * @implSpec The implementation in this class just returns {@link
121 * #DEFAULT_VALUE}; subclasses will commonly override this method.
122 *
123 * @param e the element to process
124 * @param p a visitor-specified parameter
125 * @return {@code DEFAULT_VALUE} unless overridden
126 */
127 protected R defaultAction(Element e, P p) {
128 return DEFAULT_VALUE;
129 }
130
131 /**
132 * {@inheritDoc}
133 *
134 * @implSpec This implementation calls {@code defaultAction}.
135 *
136 * @param e {@inheritDoc}
137 * @param p {@inheritDoc}
138 * @return {@inheritDoc}
139 */
140 public R visitPackage(PackageElement e, P p) {
141 return defaultAction(e, p);
142 }
143
144 /**
145 * {@inheritDoc}
146 *
147 * @implSpec This implementation calls {@code defaultAction}.
148 *
149 * @param e {@inheritDoc}
150 * @param p {@inheritDoc}
151 * @return {@inheritDoc}
152 */
153 public R visitType(TypeElement e, P p) {
154 return defaultAction(e, p);
155 }
156
157 /**
158 * {@inheritDoc}
159 *
160 * @implSpec This implementation calls {@code defaultAction}, unless the
161 * element is a {@code RESOURCE_VARIABLE} in which case {@code
162 * visitUnknown} is called.
163 *
164 * @param e {@inheritDoc}
165 * @param p {@inheritDoc}
166 * @return {@inheritDoc}
167 */
168 public R visitVariable(VariableElement e, P p) {
169 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
170 return defaultAction(e, p);
171 else
172 return visitUnknown(e, p);
173 }
174
175 /**
176 * {@inheritDoc}
177 *
178 * @implSpec This implementation calls {@code defaultAction}.
179 *
180 * @param e {@inheritDoc}
181 * @param p {@inheritDoc}
182 * @return {@inheritDoc}
183 */
184 public R visitExecutable(ExecutableElement e, P p) {
185 return defaultAction(e, p);
186 }
187
188 /**
189 * {@inheritDoc}
190 *
191 * @implSpec This implementation calls {@code defaultAction}.
192 *
193 * @param e {@inheritDoc}
194 * @param p {@inheritDoc}
195 * @return {@inheritDoc}
196 */
197 public R visitTypeParameter(TypeParameterElement e, P p) {
198 return defaultAction(e, p);
199 }
200 }