1 /*
2 * Copyright (c) 2019, 2020, 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 java.util.List;
29 import java.util.ArrayList;
30 import javax.lang.model.element.*;
31 import javax.annotation.processing.SupportedSourceVersion;
32 import javax.lang.model.SourceVersion;
33 import static javax.lang.model.SourceVersion.*;
34
35 /**
36 * {@preview Associated with records, a preview feature of the Java language.
37 *
38 * This class is associated with <i>records</i>, a preview
39 * feature of the Java language. Preview features
40 * may be removed in a future release, or upgraded to permanent
41 * features of the Java language.}
42 *
43 * A scanning visitor of program elements with default behavior
44 * appropriate for the {@link SourceVersion#RELEASE_14 RELEASE_14}
45 * source version.
46 *
47 * The <code>visit<i>Xyz</i></code> methods in this
48 * class scan their component elements by calling {@code scan} on
49 * their {@linkplain Element#getEnclosedElements enclosed elements},
50 * {@linkplain ExecutableElement#getParameters parameters}, etc., as
51 * indicated in the individual method specifications. A subclass can
52 * control the order elements are visited by overriding the
53 * <code>visit<i>Xyz</i></code> methods. Note that clients of a scanner
54 * may get the desired behavior be invoking {@code v.scan(e, p)} rather
55 * than {@code v.visit(e, p)} on the root objects of interest.
56 *
57 * <p>When a subclass overrides a <code>visit<i>Xyz</i></code> method, the
58 * new method can cause the enclosed elements to be scanned in the
59 * default way by calling <code>super.visit<i>Xyz</i></code>. In this
60 * fashion, the concrete visitor can control the ordering of traversal
61 * over the component elements with respect to the additional
62 * processing; for example, consistently calling
63 * <code>super.visit<i>Xyz</i></code> at the start of the overridden
64 * methods will yield a preorder traversal, etc. If the component
65 * elements should be traversed in some other order, instead of
66 * calling <code>super.visit<i>Xyz</i></code>, an overriding visit method
67 * should call {@code scan} with the elements in the desired order.
68 *
69 * @apiNote
70 * Methods in this class may be overridden subject to their
71 * general contract.
72 *
73 * @param <R> the return type of this visitor's methods. Use {@link
74 * Void} for visitors that do not need to return results.
75 * @param <P> the type of the additional parameter to this visitor's
76 * methods. Use {@code Void} for visitors that do not need an
77 * additional parameter.
78 *
79 * @see <a href="ElementScanner6.html#note_for_subclasses"><strong>Compatibility note for subclasses</strong></a>
80 * @see ElementScanner6
81 * @see ElementScanner7
82 * @see ElementScanner8
83 * @see ElementScanner9
84 * @since 14
85 */
86 @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.RECORDS,
87 essentialAPI=false)
88 @SupportedSourceVersion(RELEASE_15)
89 public class ElementScanner14<R, P> extends ElementScanner9<R, P> {
90 /**
91 * Constructor for concrete subclasses; uses {@code null} for the
92 * default value.
93 */
94 protected ElementScanner14(){
95 super(null);
96 }
97
98 /**
99 * Constructor for concrete subclasses; uses the argument for the
100 * default value.
101 *
102 * @param defaultValue the default value
103 */
104 protected ElementScanner14(R defaultValue){
105 super(defaultValue);
106 }
107
108 /**
109 * {@inheritDoc}
110 *
111 * @implSpec This implementation scans the type parameters, if
112 * any, and then the enclosed elements.
113 *
114 *
115 * @param e {@inheritDoc}
116 * @param p {@inheritDoc}
117 * @return the result of scanning
118 */
119 @Override
120 public R visitType(TypeElement e, P p) {
121 return scan(createScanningList(e, e.getEnclosedElements()), p);
122 }
123
124 /**
125 * {@inheritDoc}
126 *
127 * @implSpec This implementation first scans the type parameters, if any, and then
128 * the parameters.
129 *
130 * @param e {@inheritDoc}
131 * @param p {@inheritDoc}
132 * @return the result of scanning
133 */
134 public R visitExecutable(ExecutableElement e, P p) {
135 return scan(createScanningList(e, e.getParameters()), p);
136 }
137
138 private List<? extends Element> createScanningList(Parameterizable element,
139 List<? extends Element> toBeScanned) {
140 var typeParameters = element.getTypeParameters();
141 if (typeParameters.isEmpty()) {
142 return toBeScanned;
143 } else {
144 List<Element> scanningList = new ArrayList<>(typeParameters);
145 scanningList.addAll(toBeScanned);
146 return scanningList;
147 }
148 }
149
150 /**
151 * {@inheritDoc}
152 *
153 * @implSpec This implementation scans the enclosed elements.
154 *
155 * @param e the element to visit
156 * @param p a visitor-specified parameter
157 * @return the result of the scan
158 */
159 @SuppressWarnings("preview")
160 @Override
161 public R visitRecordComponent(RecordComponentElement e, P p) {
162 return scan(e.getEnclosedElements(), p);
163 }
164 }