1 /*
2 * Copyright (c) 2010, 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 scanning visitor of program elements with default behavior
36 * appropriate for the {@link SourceVersion#RELEASE_7 RELEASE_7}
37 * source version. The <code>visit<i>XYZ</i></code> 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 * <code>visit<i>XYZ</i></code> 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 <code>visit<i>XYZ</i></code> method, the
48 * new method can cause the enclosed elements to be scanned in the
49 * default way by calling <code>super.visit<i>XYZ</i></code>. 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 * <code>super.visit<i>XYZ</i></code> 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 <code>super.visit<i>XYZ</i></code>, 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 * @see ElementScanner6
88 * @see ElementScanner8
89 * @see ElementScanner9
90 * @since 1.7
91 */
92 @SuppressWarnings("deprecation") // Superclass deprecated
93 @SupportedSourceVersion(RELEASE_7)
94 public class ElementScanner7<R, P> extends ElementScanner6<R, P> {
95 /**
96 * Constructor for concrete subclasses; uses {@code null} for the
97 * default value.
98 */
99 protected ElementScanner7(){
100 super(null);
101 }
102
103 /**
104 * Constructor for concrete subclasses; uses the argument for the
105 * default value.
106 *
107 * @param defaultValue the default value
108 */
109 protected ElementScanner7(R defaultValue){
110 super(defaultValue);
111 }
112
113 /**
114 * This implementation scans the enclosed elements.
115 *
116 * @param e {@inheritDoc}
117 * @param p {@inheritDoc}
118 * @return the result of scanning
119 */
120 @Override
121 public R visitVariable(VariableElement e, P p) {
122 return scan(e.getEnclosedElements(), p);
123 }
124 }