001: /*
002: * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package javax.lang.model.type;
027:
028: import javax.lang.model.element.*;
029:
030: /**
031: * A visitor of types, in the style of the
032: * visitor design pattern. Classes implementing this
033: * interface are used to operate on a type when the kind of
034: * type is unknown at compile time. When a visitor is passed to a
035: * type's {@link TypeMirror#accept accept} method, the <tt>visit<i>XYZ</i></tt>
036: * method most applicable to that type is invoked.
037: *
038: * <p> Classes implementing this interface may or may not throw a
039: * {@code NullPointerException} if the additional parameter {@code p}
040: * is {@code null}; see documentation of the implementing class for
041: * details.
042: *
043: * <p> <b>WARNING:</b> It is possible that methods will be added to
044: * this interface to accommodate new, currently unknown, language
045: * structures added to future versions of the Java™ programming
046: * language. Therefore, visitor classes directly implementing this
047: * interface may be source incompatible with future versions of the
048: * platform. To avoid this source incompatibility, visitor
049: * implementations are encouraged to instead extend the appropriate
050: * abstract visitor class that implements this interface. However, an
051: * API should generally use this visitor interface as the type for
052: * parameters, return type, etc. rather than one of the abstract
053: * classes.
054: *
055: * @param <R> the return type of this visitor's methods. Use {@link
056: * Void} for visitors that do not need to return results.
057: * @param <P> the type of the additional parameter to this visitor's
058: * methods. Use {@code Void} for visitors that do not need an
059: * additional parameter.
060: *
061: * @author Joseph D. Darcy
062: * @author Scott Seligman
063: * @author Peter von der Ahé
064: * @version 1.11 07/05/05
065: * @since 1.6
066: */
067: public interface TypeVisitor<R, P> {
068: /**
069: * Visits a type.
070: * @param t the type to visit
071: * @param p a visitor-specified parameter
072: * @return a visitor-specified result
073: */
074: R visit(TypeMirror t, P p);
075:
076: /**
077: * A convenience method equivalent to {@code v.visit(t, null)}.
078: * @param t the element to visit
079: * @return a visitor-specified result
080: */
081: R visit(TypeMirror t);
082:
083: /**
084: * Visits a primitive type.
085: * @param t the type to visit
086: * @param p a visitor-specified parameter
087: * @return a visitor-specified result
088: */
089: R visitPrimitive(PrimitiveType t, P p);
090:
091: /**
092: * Visits the null type.
093: * @param t the type to visit
094: * @param p a visitor-specified parameter
095: * @return a visitor-specified result
096: */
097: R visitNull(NullType t, P p);
098:
099: /**
100: * Visits an array type.
101: * @param t the type to visit
102: * @param p a visitor-specified parameter
103: * @return a visitor-specified result
104: */
105: R visitArray(ArrayType t, P p);
106:
107: /**
108: * Visits a declared type.
109: * @param t the type to visit
110: * @param p a visitor-specified parameter
111: * @return a visitor-specified result
112: */
113: R visitDeclared(DeclaredType t, P p);
114:
115: /**
116: * Visits an error type.
117: * @param t the type to visit
118: * @param p a visitor-specified parameter
119: * @return a visitor-specified result
120: */
121: R visitError(ErrorType t, P p);
122:
123: /**
124: * Visits a type variable.
125: * @param t the type to visit
126: * @param p a visitor-specified parameter
127: * @return a visitor-specified result
128: */
129: R visitTypeVariable(TypeVariable t, P p);
130:
131: /**
132: * Visits a wildcard type.
133: * @param t the type to visit
134: * @param p a visitor-specified parameter
135: * @return a visitor-specified result
136: */
137: R visitWildcard(WildcardType t, P p);
138:
139: /**
140: * Visits an executable type.
141: * @param t the type to visit
142: * @param p a visitor-specified parameter
143: * @return a visitor-specified result
144: */
145: R visitExecutable(ExecutableType t, P p);
146:
147: /**
148: * Visits a {@link NoType} instance.
149: * @param t the type to visit
150: * @param p a visitor-specified parameter
151: * @return a visitor-specified result
152: */
153: R visitNoType(NoType t, P p);
154:
155: /**
156: * Visits an unknown kind of type.
157: * This can occur if the language evolves and new kinds
158: * of types are added to the {@code TypeMirror} hierarchy.
159: * @param t the type to visit
160: * @param p a visitor-specified parameter
161: * @return a visitor-specified result
162: * @throws UnknownTypeException
163: * a visitor implementation may optionally throw this exception
164: */
165: R visitUnknown(TypeMirror t, P p);
166: }
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