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
29 import javax.lang.model.element.*;
30 import javax.annotation.processing.SupportedSourceVersion;
31 import javax.lang.model.element.*;
32 import static javax.lang.model.element.ElementKind.*;
33 import static javax.lang.model.SourceVersion.*;
34 import javax.lang.model.SourceVersion;
35
36
37 /**
38 * A skeletal visitor of program elements with default behavior
39 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
40 * source version.
41 *
42 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
43 * implemented by this class may have methods added to it in the
44 * future to accommodate new, currently unknown, language structures
45 * added to future versions of the Java™ programming language.
46 * Therefore, methods whose names begin with {@code "visit"} may be
47 * added to this class in the future; to avoid incompatibilities,
48 * classes which extend this class should not declare any instance
49 * methods with names beginning with {@code "visit"}.
50 *
51 * <p>When such a new visit method is added, the default
52 * implementation in this class will be to call the {@link
53 * #visitUnknown visitUnknown} method. A new abstract element visitor
54 * class will also be introduced to correspond to the new language
55 * level; this visitor will have different default behavior for the
56 * visit method in question. When the new visitor is introduced, all
57 * or portions of this visitor may be deprecated.
58 *
59 * @param <R> the return type of this visitor's methods. Use {@link
60 * Void} for visitors that do not need to return results.
61 * @param <P> the type of the additional parameter to this visitor's
62 * methods. Use {@code Void} for visitors that do not need an
63 * additional parameter.
64 *
65 * @author Joseph D. Darcy
66 * @author Scott Seligman
67 * @author Peter von der Ahé
68 *
69 * @see AbstractElementVisitor7
70 * @see AbstractElementVisitor8
71 * @since 1.6
72 */
73 @SupportedSourceVersion(RELEASE_6)
74 public abstract class AbstractElementVisitor6<R, P> implements ElementVisitor<R, P> {
75 /**
76 * Constructor for concrete subclasses to call.
77 */
78 protected AbstractElementVisitor6(){}
79
80 /**
81 * Visits any program element as if by passing itself to that
82 * element's {@link Element#accept accept} method. The invocation
83 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
84 * p)}.
85 *
86 * @param e the element to visit
87 * @param p a visitor-specified parameter
88 * @return a visitor-specified result
89 */
90 public final R visit(Element e, P p) {
91 return e.accept(this, p);
92 }
93
94 /**
95 * Visits any program element as if by passing itself to that
96 * element's {@link Element#accept accept} method and passing
97 * {@code null} for the additional parameter. The invocation
98 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
99 * null)}.
100 *
101 * @param e the element to visit
102 * @return a visitor-specified result
103 */
104 public final R visit(Element e) {
105 return e.accept(this, null);
106 }
107
108 /**
109 * {@inheritDoc}
110 *
111 * <p> The default implementation of this method in
112 * {@code AbstractElementVisitor6} will always throw
113 * {@code UnknownElementException}.
114 * This behavior is not required of a subclass.
115 *
116 * @param e the element to visit
117 * @param p a visitor-specified parameter
118 * @return a visitor-specified result
119 * @throws UnknownElementException
120 * a visitor implementation may optionally throw this exception
121 */
122 public R visitUnknown(Element e, P p) {
123 throw new UnknownElementException(e, p);
124 }
125 }