1 /*
2 * Copyright (c) 2005, 2017, 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 * @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 * @deprecated Release 6 is obsolete; update to a visitor for a newer
95 * release level.
96 */
97 @Deprecated(since="9")
98 protected SimpleElementVisitor6(){
99 DEFAULT_VALUE = null;
100 }
101
102 /**
103 * Constructor for concrete subclasses; uses the argument for the
104 * default value.
105 *
106 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
107 * @deprecated Release 6 is obsolete; update to a visitor for a newer
108 * release level.
109 */
110 @Deprecated(since="9")
111 protected SimpleElementVisitor6(R defaultValue){
112 DEFAULT_VALUE = defaultValue;
113 }
114 /**
115 * The default action for visit methods.
116 *
117 * @implSpec The implementation in this class just returns {@link
118 * #DEFAULT_VALUE}; subclasses will commonly override this method.
119 *
120 * @param e the element to process
121 * @param p a visitor-specified parameter
122 * @return {@code DEFAULT_VALUE} unless overridden
123 */
124 protected R defaultAction(Element e, P p) {
125 return DEFAULT_VALUE;
126 }
127
128 /**
129 * {@inheritDoc}
130 *
131 * @implSpec This implementation calls {@code defaultAction}.
132 *
133 * @param e {@inheritDoc}
134 * @param p {@inheritDoc}
135 * @return {@inheritDoc}
136 */
137 public R visitPackage(PackageElement e, P p) {
138 return defaultAction(e, p);
139 }
140
141 /**
142 * {@inheritDoc}
143 *
144 * @implSpec This implementation calls {@code defaultAction}.
145 *
146 * @param e {@inheritDoc}
147 * @param p {@inheritDoc}
148 * @return {@inheritDoc}
149 */
150 public R visitType(TypeElement e, P p) {
151 return defaultAction(e, p);
152 }
153
154 /**
155 * {@inheritDoc}
156 *
157 * @implSpec This implementation calls {@code defaultAction}, unless the
158 * element is a {@code RESOURCE_VARIABLE} in which case {@code
159 * visitUnknown} is called.
160 *
161 * @param e {@inheritDoc}
162 * @param p {@inheritDoc}
163 * @return {@inheritDoc}
164 */
165 public R visitVariable(VariableElement e, P p) {
166 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
167 return defaultAction(e, p);
168 else
169 return visitUnknown(e, p);
170 }
171
172 /**
173 * {@inheritDoc}
174 *
175 * @implSpec This implementation calls {@code defaultAction}.
176 *
177 * @param e {@inheritDoc}
178 * @param p {@inheritDoc}
179 * @return {@inheritDoc}
180 */
181 public R visitExecutable(ExecutableElement e, P p) {
182 return defaultAction(e, p);
183 }
184
185 /**
186 * {@inheritDoc}
187 *
188 * @implSpec This implementation calls {@code defaultAction}.
189 *
190 * @param e {@inheritDoc}
191 * @param p {@inheritDoc}
192 * @return {@inheritDoc}
193 */
194 public R visitTypeParameter(TypeParameterElement e, P p) {
195 return defaultAction(e, p);
196 }
197 }