Tue, 09 Oct 2012 19:10:00 -0700
8000663: clean up langtools imports
Reviewed-by: darcy
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
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24 */
26 package javax.lang.model.util;
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.*;
34 /**
35 * A scanning visitor of program elements with default behavior
36 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
37 * source version. The <tt>visit<i>XYZ</i></tt> methods in this
38 * class scan their component elements by calling {@code scan} on
39 * their {@linkplain Element#getEnclosedElements enclosed elements},
40 * {@linkplain ExecutableElement#getParameters parameters}, etc., as
41 * indicated in the individual method specifications. A subclass can
42 * control the order elements are visited by overriding the
43 * <tt>visit<i>XYZ</i></tt> methods. Note that clients of a scanner
44 * may get the desired behavior be invoking {@code v.scan(e, p)} rather
45 * than {@code v.visit(e, p)} on the root objects of interest.
46 *
47 * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the
48 * new method can cause the enclosed elements to be scanned in the
49 * default way by calling <tt>super.visit<i>XYZ</i></tt>. In this
50 * fashion, the concrete visitor can control the ordering of traversal
51 * over the component elements with respect to the additional
52 * processing; for example, consistently calling
53 * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden
54 * methods will yield a preorder traversal, etc. If the component
55 * elements should be traversed in some other order, instead of
56 * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method
57 * should call {@code scan} with the elements in the desired order.
58 *
59 * <p> Methods in this class may be overridden subject to their
60 * general contract. Note that annotating methods in concrete
61 * subclasses with {@link java.lang.Override @Override} will help
62 * ensure that methods are overridden as intended.
63 *
64 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
65 * implemented by this class may have methods added to it in the
66 * future to accommodate new, currently unknown, language structures
67 * added to future versions of the Java™ programming language.
68 * Therefore, methods whose names begin with {@code "visit"} may be
69 * added to this class in the future; to avoid incompatibilities,
70 * classes which extend this class should not declare any instance
71 * methods with names beginning with {@code "visit"}.
72 *
73 * <p>When such a new visit method is added, the default
74 * implementation in this class will be to call the {@link
75 * #visitUnknown visitUnknown} method. A new element scanner visitor
76 * class will also be introduced to correspond to the new language
77 * level; this visitor will have different default behavior for the
78 * visit method in question. When the new visitor is introduced, all
79 * or portions of this visitor may be deprecated.
80 *
81 * @param <R> the return type of this visitor's methods. Use {@link
82 * Void} for visitors that do not need to return results.
83 * @param <P> the type of the additional parameter to this visitor's
84 * methods. Use {@code Void} for visitors that do not need an
85 * additional parameter.
86 *
87 * @author Joseph D. Darcy
88 * @author Scott Seligman
89 * @author Peter von der Ahé
90 *
91 * @see ElementScanner7
92 * @see ElementScanner8
93 * @since 1.6
94 */
95 @SupportedSourceVersion(RELEASE_6)
96 public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {
97 /**
98 * The specified default value.
99 */
100 protected final R DEFAULT_VALUE;
102 /**
103 * Constructor for concrete subclasses; uses {@code null} for the
104 * default value.
105 */
106 protected ElementScanner6(){
107 DEFAULT_VALUE = null;
108 }
110 /**
111 * Constructor for concrete subclasses; uses the argument for the
112 * default value.
113 */
114 protected ElementScanner6(R defaultValue){
115 DEFAULT_VALUE = defaultValue;
116 }
118 /**
119 * Iterates over the given elements and calls {@link
120 * #scan(Element, Object) scan(Element, P)} on each one. Returns
121 * the result of the last call to {@code scan} or {@code
122 * DEFAULT_VALUE} for an empty iterable.
123 *
124 * @param iterable the elements to scan
125 * @param p additional parameter
126 * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements
127 */
128 public final R scan(Iterable<? extends Element> iterable, P p) {
129 R result = DEFAULT_VALUE;
130 for(Element e : iterable)
131 result = scan(e, p);
132 return result;
133 }
135 /**
136 * Processes an element by calling {@code e.accept(this, p)};
137 * this method may be overridden by subclasses.
138 * @return the result of visiting {@code e}.
139 */
140 public R scan(Element e, P p) {
141 return e.accept(this, p);
142 }
144 /**
145 * Convenience method equivalent to {@code v.scan(e, null)}.
146 * @return the result of scanning {@code e}.
147 */
148 public final R scan(Element e) {
149 return scan(e, null);
150 }
152 /**
153 * {@inheritDoc} This implementation scans the enclosed elements.
154 *
155 * @param e {@inheritDoc}
156 * @param p {@inheritDoc}
157 * @return the result of scanning
158 */
159 public R visitPackage(PackageElement e, P p) {
160 return scan(e.getEnclosedElements(), p);
161 }
163 /**
164 * {@inheritDoc} This implementation scans the enclosed elements.
165 *
166 * @param e {@inheritDoc}
167 * @param p {@inheritDoc}
168 * @return the result of scanning
169 */
170 public R visitType(TypeElement e, P p) {
171 return scan(e.getEnclosedElements(), p);
172 }
174 /**
175 * {@inheritDoc}
176 *
177 * This implementation scans the enclosed elements, unless the
178 * element is a {@code RESOURCE_VARIABLE} in which case {@code
179 * visitUnknown} is called.
180 *
181 * @param e {@inheritDoc}
182 * @param p {@inheritDoc}
183 * @return the result of scanning
184 */
185 public R visitVariable(VariableElement e, P p) {
186 if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
187 return scan(e.getEnclosedElements(), p);
188 else
189 return visitUnknown(e, p);
190 }
192 /**
193 * {@inheritDoc} This implementation scans the parameters.
194 *
195 * @param e {@inheritDoc}
196 * @param p {@inheritDoc}
197 * @return the result of scanning
198 */
199 public R visitExecutable(ExecutableElement e, P p) {
200 return scan(e.getParameters(), p);
201 }
203 /**
204 * {@inheritDoc} This implementation scans the enclosed elements.
205 *
206 * @param e {@inheritDoc}
207 * @param p {@inheritDoc}
208 * @return the result of scanning
209 */
210 public R visitTypeParameter(TypeParameterElement e, P p) {
211 return scan(e.getEnclosedElements(), p);
212 }
213 }