1 /*
2 * Copyright (c) 2005, 2019, 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 * <p> Methods in this class may be overridden subject to their
47 * general contract. Note that annotating methods in concrete
48 * subclasses with {@link java.lang.Override @Override} will help
49 * ensure that methods are overridden as intended.
50 *
51 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
52 * implemented by this class may have methods added to it in the
53 * future to accommodate new, currently unknown, language structures
54 * added to future versions of the Java™ programming language.
55 * Therefore, methods whose names begin with {@code "visit"} may be
56 * added to this class in the future; to avoid incompatibilities,
57 * classes which extend this class should not declare any instance
58 * methods with names beginning with {@code "visit"}.
59 *
60 * <p>When such a new visit method is added, the default
61 * implementation in this class will be to call the {@link
62 * #visitUnknown visitUnknown} method. A new simple element visitor
63 * class will also be introduced to correspond to the new language
64 * level; this visitor will have different default behavior for the
65 * visit method in question. When the new visitor is introduced, all
66 * or portions of this visitor may be deprecated.
67 *
68 * @param <R> the return type of this visitor's methods. Use {@code Void}
69 * for visitors that do not need to return results.
70 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
71 * for visitors that do not need an additional parameter.
72 *
73 * @author Joseph D. Darcy
74 * @author Scott Seligman
75 * @author Peter von der Ahé
76 *
77 * @see SimpleElementVisitor7
78 * @see SimpleElementVisitor8
79 * @see SimpleElementVisitor9
80 * @see SimpleElementVisitor14
81 * @since 1.6
82 */
83 @SupportedSourceVersion(RELEASE_6)
84 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
85 /**
86 * Default value to be returned; {@link #defaultAction
87 * defaultAction} returns this value unless the method is
88 * overridden.
89 */
90 protected final R DEFAULT_VALUE;
91
92 /**
93 * Constructor for concrete subclasses; uses {@code null} for the
94 * default value.
95 * @deprecated Release 6 is obsolete; update to a visitor for a newer
96 * release level.
97 */
98 @Deprecated(since="9")
99 protected SimpleElementVisitor6(){
100 DEFAULT_VALUE = null;
101 }
102
103 /**
104 * Constructor for concrete subclasses; uses the argument for the
105 * default value.
106 *
107 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
108 * @deprecated Release 6 is obsolete; update to a visitor for a newer
109 * release level.
110 */
111 @Deprecated(since="9")
112 protected SimpleElementVisitor6(R defaultValue){
113 DEFAULT_VALUE = defaultValue;
114 }
115 /**
116 * The default action for visit methods.
117 *
118 * @implSpec The implementation in this class just returns {@link
119 * #DEFAULT_VALUE}; subclasses will commonly override this method.
120 *
121 * @param e the element to process
122 * @param p a visitor-specified parameter
123 * @return {@code DEFAULT_VALUE} unless overridden
124 */
125 protected R defaultAction(Element e, P p) {
126 return DEFAULT_VALUE;
127 }
128
129 /**
130 * {@inheritDoc}
131 *
132 * @implSpec This implementation calls {@code defaultAction}.
133 *
134 * @param e {@inheritDoc}
135 * @param p {@inheritDoc}
136 * @return {@inheritDoc}
137 */
138 public R visitPackage(PackageElement e, P p) {
139 return defaultAction(e, p);
140 }
141
142 /**
143 * {@inheritDoc}
144 *
145 * @implSpec This implementation calls {@code defaultAction}.
146 *
147 * @param e {@inheritDoc}
148 * @param p {@inheritDoc}
149 * @return {@inheritDoc}
150 */
151 public R visitType(TypeElement e, P p) {
152 return defaultAction(e, p);
153 }
154
155 /**
156 * {@inheritDoc}
157 *
158 * @implSpec This implementation calls {@code defaultAction}, unless the
159 * element is a {@code RESOURCE_VARIABLE} in which case {@code
160 * visitUnknown} is called.
161 *
162 * @param e {@inheritDoc}
163 * @param p {@inheritDoc}
164 * @return {@inheritDoc}
165 */
166 public R visitVariable(VariableElement e, P p) {
167 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
168 return defaultAction(e, p);
169 else
170 return visitUnknown(e, p);
171 }
172
173 /**
174 * {@inheritDoc}
175 *
176 * @implSpec This implementation calls {@code defaultAction}.
177 *
178 * @param e {@inheritDoc}
179 * @param p {@inheritDoc}
180 * @return {@inheritDoc}
181 */
182 public R visitExecutable(ExecutableElement e, P p) {
183 return defaultAction(e, p);
184 }
185
186 /**
187 * {@inheritDoc}
188 *
189 * @implSpec This implementation calls {@code defaultAction}.
190 *
191 * @param e {@inheritDoc}
192 * @param p {@inheritDoc}
193 * @return {@inheritDoc}
194 */
195 public R visitTypeParameter(TypeParameterElement e, P p) {
196 return defaultAction(e, p);
197 }
198 }