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.util;
  27 
  28 import javax.lang.model.type.*;
  29 
  30 /**
  31  * A skeletal visitor of types with default behavior appropriate for
  32  * the {@link javax.lang.model.SourceVersion#RELEASE_6 RELEASE_6}
  33  * source version.
  34  *
  35  * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented
  36  * by this class may have methods added to it in the future to
  37  * accommodate new, currently unknown, language structures added to
  38  * future versions of the Java&trade; programming language.
  39  * Therefore, methods whose names begin with {@code "visit"} may be
  40  * added to this class in the future; to avoid incompatibilities,
  41  * classes which extend this class should not declare any instance
  42  * methods with names beginning with {@code "visit"}.
  43  *
  44  * <p>When such a new visit method is added, the default
  45  * implementation in this class will be to call the {@link
  46  * #visitUnknown visitUnknown} method.  A new abstract type visitor
  47  * class will also be introduced to correspond to the new language
  48  * level; this visitor will have different default behavior for the
  49  * visit method in question.  When the new visitor is introduced, all
  50  * or portions of this visitor may be deprecated.
  51  *
  52  * @param <R> the return type of this visitor's methods.  Use {@link
  53  *            Void} for visitors that do not need to return results.
  54  * @param <P> the type of the additional parameter to this visitor's
  55  *            methods.  Use {@code Void} for visitors that do not need an
  56  *            additional parameter.
  57  *
  58  * @author Joseph D. Darcy
  59  * @author Scott Seligman
  60  * @author Peter von der Ah&eacute;
  61  *
  62  * @see AbstractTypeVisitor7
  63  * @see AbstractTypeVisitor8
  64  * @since 1.6
  65  */
  66 public abstract class AbstractTypeVisitor6<R, P> implements TypeVisitor<R, P> {
  67     /**
  68      * Constructor for concrete subclasses to call.
  69      */
  70     protected AbstractTypeVisitor6() {}
  71 
  72     /**
  73      * Visits any type mirror as if by passing itself to that type
  74      * mirror's {@link TypeMirror#accept accept} method.  The
  75      * invocation {@code v.visit(t, p)} is equivalent to {@code
  76      * t.accept(v, p)}.
  77      *
  78      * @param t  the type to visit
  79      * @param p  a visitor-specified parameter
  80      * @return a visitor-specified result
  81      */
  82     public final R visit(TypeMirror t, P p) {
  83         return t.accept(this, p);
  84     }
  85 
  86     /**
  87      * Visits any type mirror as if by passing itself to that type
  88      * mirror's {@link TypeMirror#accept accept} method and passing
  89      * {@code null} for the additional parameter.  The invocation
  90      * {@code v.visit(t)} is equivalent to {@code t.accept(v, null)}.
  91      *
  92      * @param t  the type to visit
  93      * @return a visitor-specified result
  94      */
  95     public final R visit(TypeMirror t) {
  96         return t.accept(this, null);
  97     }
  98 
  99     /**
 100      * Visits a {@code UnionType} element by calling {@code
 101      * visitUnknown}.
 102 
 103      * @param t  {@inheritDoc}
 104      * @param p  {@inheritDoc}
 105      * @return the result of {@code visitUnknown}
 106      *
 107      * @since 1.7
 108      */
 109     public R visitUnion(UnionType t, P p) {
 110         return visitUnknown(t, p);
 111     }
 112 
 113     /**
 114      * {@inheritDoc}
 115      *
 116      * <p> The default implementation of this method in {@code
 117      * AbstractTypeVisitor6} will always throw {@code
 118      * UnknownTypeException}.  This behavior is not required of a
 119      * subclass.
 120      *
 121      * @param t  the type to visit
 122      * @return a visitor-specified result
 123      * @throws UnknownTypeException
 124      *  a visitor implementation may optionally throw this exception
 125      */
 126     public R visitUnknown(TypeMirror t, P p) {
 127         throw new UnknownTypeException(t, p);
 128     }
 129 }