1 /*
2 * Copyright (c) 2005, 2012, 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.annotation.processing.SupportedSourceVersion;
29 import javax.lang.model.SourceVersion;
30 import javax.lang.model.element.*;
31 import static javax.lang.model.SourceVersion.*;
32
33
34 /**
35 * A skeletal visitor of program elements with default behavior
36 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
37 * source version.
38 *
39 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
40 * implemented by this class may have methods added to it in the
41 * future to accommodate new, currently unknown, language structures
42 * added to future versions of the Java™ programming language.
43 * Therefore, methods whose names begin with {@code "visit"} may be
44 * added to this class in the future; to avoid incompatibilities,
45 * classes which extend this class should not declare any instance
46 * methods with names beginning with {@code "visit"}.
47 *
48 * <p>When such a new visit method is added, the default
49 * implementation in this class will be to call the {@link
50 * #visitUnknown visitUnknown} method. A new abstract element visitor
51 * class will also be introduced to correspond to the new language
52 * level; this visitor will have different default behavior for the
53 * visit method in question. When the new visitor is introduced, all
54 * or portions of this visitor may be deprecated.
55 *
56 * @param <R> the return type of this visitor's methods. Use {@link
57 * Void} for visitors that do not need to return results.
58 * @param <P> the type of the additional parameter to this visitor's
59 * methods. Use {@code Void} for visitors that do not need an
60 * additional parameter.
61 *
62 * @author Joseph D. Darcy
63 * @author Scott Seligman
64 * @author Peter von der Ahé
65 *
66 * @see AbstractElementVisitor7
67 * @see AbstractElementVisitor8
68 * @since 1.6
69 */
70 @SupportedSourceVersion(RELEASE_6)
71 public abstract class AbstractElementVisitor6<R, P> implements ElementVisitor<R, P> {
72 /**
73 * Constructor for concrete subclasses to call.
74 */
75 protected AbstractElementVisitor6(){}
76
77 /**
78 * Visits any program element as if by passing itself to that
79 * element's {@link Element#accept accept} method. The invocation
80 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
81 * p)}.
82 *
83 * @param e the element to visit
84 * @param p a visitor-specified parameter
85 * @return a visitor-specified result
86 */
87 public final R visit(Element e, P p) {
88 return e.accept(this, p);
89 }
90
91 /**
92 * Visits any program element as if by passing itself to that
93 * element's {@link Element#accept accept} method and passing
94 * {@code null} for the additional parameter. The invocation
95 * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,
96 * null)}.
97 *
98 * @param e the element to visit
99 * @return a visitor-specified result
100 */
101 public final R visit(Element e) {
102 return e.accept(this, null);
103 }
104
105 /**
106 * {@inheritDoc}
107 *
108 * <p> The default implementation of this method in
109 * {@code AbstractElementVisitor6} will always throw
110 * {@code UnknownElementException}.
111 * This behavior is not required of a subclass.
112 *
113 * @param e the element to visit
114 * @param p a visitor-specified parameter
115 * @return a visitor-specified result
116 * @throws UnknownElementException
117 * a visitor implementation may optionally throw this exception
118 */
119 public R visitUnknown(Element e, P p) {
120 throw new UnknownElementException(e, p);
121 }
122 }