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.type;
27
28 import javax.lang.model.element.*;
29
30 /**
31 * A visitor of types, in the style of the
32 * visitor design pattern. Classes implementing this
33 * interface are used to operate on a type when the kind of
34 * type is unknown at compile time. When a visitor is passed to a
35 * type's {@link TypeMirror#accept accept} method, the <tt>visit<i>XYZ</i></tt>
36 * method most applicable to that type is invoked.
37 *
38 * <p> Classes implementing this interface may or may not throw a
39 * {@code NullPointerException} if the additional parameter {@code p}
40 * is {@code null}; see documentation of the implementing class for
41 * details.
42 *
43 * <p> <b>WARNING:</b> It is possible that methods will be added to
44 * this interface to accommodate new, currently unknown, language
45 * structures added to future versions of the Java™ programming
46 * language. Therefore, visitor classes directly implementing this
47 * interface may be source incompatible with future versions of the
48 * platform. To avoid this source incompatibility, visitor
49 * implementations are encouraged to instead extend the appropriate
50 * abstract visitor class that implements this interface. However, an
51 * API should generally use this visitor interface as the type for
52 * parameters, return type, etc. rather than one of the abstract
53 * classes.
54 *
55 * @param <R> the return type of this visitor's methods. Use {@link
56 * Void} for visitors that do not need to return results.
57 * @param <P> the type of the additional parameter to this visitor's
58 * methods. Use {@code Void} for visitors that do not need an
59 * additional parameter.
60 *
61 * @author Joseph D. Darcy
62 * @author Scott Seligman
63 * @author Peter von der Ahé
64 * @since 1.6
65 */
66 public interface TypeVisitor<R, P> {
67 /**
68 * Visits a type.
69 * @param t the type to visit
70 * @param p a visitor-specified parameter
71 * @return a visitor-specified result
72 */
73 R visit(TypeMirror t, P p);
74
75 /**
76 * A convenience method equivalent to {@code v.visit(t, null)}.
77 * @param t the element to visit
78 * @return a visitor-specified result
79 */
80 R visit(TypeMirror t);
81
82 /**
83 * Visits a primitive type.
84 * @param t the type to visit
85 * @param p a visitor-specified parameter
86 * @return a visitor-specified result
87 */
88 R visitPrimitive(PrimitiveType t, P p);
89
90 /**
91 * Visits the null type.
92 * @param t the type to visit
93 * @param p a visitor-specified parameter
94 * @return a visitor-specified result
95 */
96 R visitNull(NullType t, P p);
97
98 /**
99 * Visits an array type.
100 * @param t the type to visit
101 * @param p a visitor-specified parameter
102 * @return a visitor-specified result
103 */
104 R visitArray(ArrayType t, P p);
105
106 /**
107 * Visits a declared type.
108 * @param t the type to visit
109 * @param p a visitor-specified parameter
110 * @return a visitor-specified result
111 */
112 R visitDeclared(DeclaredType t, P p);
113
114 /**
115 * Visits an error type.
116 * @param t the type to visit
117 * @param p a visitor-specified parameter
118 * @return a visitor-specified result
119 */
120 R visitError(ErrorType t, P p);
121
122 /**
123 * Visits a type variable.
124 * @param t the type to visit
125 * @param p a visitor-specified parameter
126 * @return a visitor-specified result
127 */
128 R visitTypeVariable(TypeVariable t, P p);
129
130 /**
131 * Visits a wildcard type.
132 * @param t the type to visit
133 * @param p a visitor-specified parameter
134 * @return a visitor-specified result
135 */
136 R visitWildcard(WildcardType t, P p);
137
138 /**
139 * Visits an executable type.
140 * @param t the type to visit
141 * @param p a visitor-specified parameter
142 * @return a visitor-specified result
143 */
144 R visitExecutable(ExecutableType t, P p);
145
146 /**
147 * Visits a {@link NoType} instance.
148 * @param t the type to visit
149 * @param p a visitor-specified parameter
150 * @return a visitor-specified result
151 */
152 R visitNoType(NoType t, P p);
153
154 /**
155 * Visits an unknown kind of type.
156 * This can occur if the language evolves and new kinds
157 * of types are added to the {@code TypeMirror} hierarchy.
158 * @param t the type to visit
159 * @param p a visitor-specified parameter
160 * @return a visitor-specified result
161 * @throws UnknownTypeException
162 * a visitor implementation may optionally throw this exception
163 */
164 R visitUnknown(TypeMirror t, P p);
165
166 /**
167 * Visits a disjunctive type.
168 *
169 * @param t the type to visit
170 * @param p a visitor-specified parameter
171 * @return a visitor-specified result
172 * @since 1.7
173 */
174 R visitDisjunctive(DisjunctiveType t, P p);
175 }