1 /*
2 * Copyright (c) 2005, 2014, 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 * <p>Note that adding a default implementation of a new visit method
69 * in a visitor class will occur instead of adding a <em>default
70 * method</em> directly in the visitor interface since a Java SE 8
71 * language feature cannot be used to this version of the API since
72 * this version is required to be runnable on Java SE 7
73 * implementations. Future versions of the API that are only required
74 * to run on Java SE 8 and later may take advantage of default methods
75 * in this situation.
76 *
77 * @param <R> the return type of this visitor's methods. Use {@code Void}
78 * for visitors that do not need to return results.
79 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void}
80 * for visitors that do not need an additional parameter.
81 *
82 * @author Joseph D. Darcy
83 * @author Scott Seligman
84 * @author Peter von der Ahé
85 *
86 * @see SimpleElementVisitor7
87 * @see SimpleElementVisitor8
88 * @see SimpleElementVisitor9
89 * @since 1.6
90 * @deprecated Release 6 is obsolete; update to a visitor for a newer
91 * release level.
92 */
93 @Deprecated
94 @SupportedSourceVersion(RELEASE_6)
95 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> {
96 /**
97 * Default value to be returned; {@link #defaultAction
98 * defaultAction} returns this value unless the method is
99 * overridden.
100 */
101 protected final R DEFAULT_VALUE;
102
103 /**
104 * Constructor for concrete subclasses; uses {@code null} for the
105 * default value.
106 */
107 protected SimpleElementVisitor6(){
108 DEFAULT_VALUE = null;
109 }
110
111 /**
112 * Constructor for concrete subclasses; uses the argument for the
113 * default value.
114 *
115 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
116 */
117 protected SimpleElementVisitor6(R defaultValue){
118 DEFAULT_VALUE = defaultValue;
119 }
120 /**
121 * The default action for visit methods. The implementation in
122 * this class just returns {@link #DEFAULT_VALUE}; subclasses will
123 * commonly override this method.
124 *
125 * @param e the element to process
126 * @param p a visitor-specified parameter
127 * @return {@code DEFAULT_VALUE} unless overridden
128 */
129 protected R defaultAction(Element e, P p) {
130 return DEFAULT_VALUE;
131 }
132
133 /**
134 * {@inheritDoc} This implementation calls {@code defaultAction}.
135 *
136 * @param e {@inheritDoc}
137 * @param p {@inheritDoc}
138 * @return the result of {@code defaultAction}
139 */
140 public R visitPackage(PackageElement e, P p) {
141 return defaultAction(e, p);
142 }
143
144 /**
145 * {@inheritDoc} This implementation calls {@code defaultAction}.
146 *
147 * @param e {@inheritDoc}
148 * @param p {@inheritDoc}
149 * @return the result of {@code defaultAction}
150 */
151 public R visitType(TypeElement e, P p) {
152 return defaultAction(e, p);
153 }
154
155 /**
156 * {@inheritDoc}
157 *
158 * 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 the result of {@code defaultAction} or {@code visitUnknown}
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} This implementation calls {@code defaultAction}.
175 *
176 * @param e {@inheritDoc}
177 * @param p {@inheritDoc}
178 * @return the result of {@code defaultAction}
179 */
180 public R visitExecutable(ExecutableElement e, P p) {
181 return defaultAction(e, p);
182 }
183
184 /**
185 * {@inheritDoc} This implementation calls {@code defaultAction}.
186 *
187 * @param e {@inheritDoc}
188 * @param p {@inheritDoc}
189 * @return the result of {@code defaultAction}
190 */
191 public R visitTypeParameter(TypeParameterElement e, P p) {
192 return defaultAction(e, p);
193 }
194 }