1 /*
   2  * Copyright (c) 2005, 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.annotation.processing.SupportedSourceVersion;
  29 import javax.lang.model.type.*;
  30 
  31 import static javax.lang.model.SourceVersion.*;
  32 
  33 /**
  34  * A skeletal visitor of types with default behavior appropriate for
  35  * the {@link javax.lang.model.SourceVersion#RELEASE_6 RELEASE_6}
  36  * source version.
  37  *
  38  * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented
  39  * by this class may have methods added to it in the future to
  40  * accommodate new, currently unknown, language structures added to
  41  * future versions of the Java&trade; programming language.
  42  * Therefore, methods whose names begin with {@code "visit"} may be
  43  * added to this class in the future; to avoid incompatibilities,
  44  * classes which extend this class should not declare any instance
  45  * methods with names beginning with {@code "visit"}.
  46  *
  47  * <p>When such a new visit method is added, the default
  48  * implementation in this class will be to call the {@link
  49  * #visitUnknown visitUnknown} method.  A new abstract type visitor
  50  * class will also be introduced to correspond to the new language
  51  * level; this visitor will have different default behavior for the
  52  * visit method in question.  When the new visitor is introduced, all
  53  * or portions of this visitor may be deprecated.
  54  *
  55  * <p>Note that adding a default implementation of a new visit method
  56  * in a visitor class will occur instead of adding a <em>default
  57  * method</em> directly in the visitor interface since a Java SE 8
  58  * language feature cannot be used to this version of the API since
  59  * this version is required to be runnable on Java SE 7
  60  * implementations.  Future versions of the API that are only required
  61  * to run on Java SE 8 and later may take advantage of default methods
  62  * in this situation.
  63  *
  64  * @param <R> the return type of this visitor's methods.  Use {@link
  65  *            Void} for visitors that do not need to return results.
  66  * @param <P> the type of the additional parameter to this visitor's
  67  *            methods.  Use {@code Void} for visitors that do not need an
  68  *            additional parameter.
  69  *
  70  * @author Joseph D. Darcy
  71  * @author Scott Seligman
  72  * @author Peter von der Ah&eacute;
  73  *
  74  * @see AbstractTypeVisitor7
  75  * @see AbstractTypeVisitor8
  76  * @see AbstractTypeVisitor9
  77  * @since 1.6
  78  */
  79 @SupportedSourceVersion(RELEASE_6)
  80 public abstract class AbstractTypeVisitor6<R, P> implements TypeVisitor<R, P> {
  81     /**
  82      * Constructor for concrete subclasses to call.
  83      * @deprecated Release 6 is obsolete; update to a visitor for a newer
  84      * release level.
  85      */
  86     @Deprecated
  87     protected AbstractTypeVisitor6() {}
  88 
  89     /**
  90      * Visits any type mirror as if by passing itself to that type
  91      * mirror's {@link TypeMirror#accept accept} method.  The
  92      * invocation {@code v.visit(t, p)} is equivalent to {@code
  93      * t.accept(v, p)}.
  94      *
  95      * @param t  the type to visit
  96      * @param p  a visitor-specified parameter
  97      * @return a visitor-specified result
  98      */
  99     public final R visit(TypeMirror t, P p) {
 100         return t.accept(this, p);
 101     }
 102 
 103     /**
 104      * Visits any type mirror as if by passing itself to that type
 105      * mirror's {@link TypeMirror#accept accept} method and passing
 106      * {@code null} for the additional parameter.  The invocation
 107      * {@code v.visit(t)} is equivalent to {@code t.accept(v, null)}.
 108      *
 109      * @param t  the type to visit
 110      * @return a visitor-specified result
 111      */
 112     public final R visit(TypeMirror t) {
 113         return t.accept(this, null);
 114     }
 115 
 116     /**
 117      * {@inheritDoc}
 118      *
 119      * @implSpec Visits a {@code UnionType} element by calling {@code
 120      * visitUnknown}.
 121      *
 122      * @param t  {@inheritDoc}
 123      * @param p  {@inheritDoc}
 124      * @return the result of {@code visitUnknown}
 125      *
 126      * @since 1.7
 127      */
 128     public R visitUnion(UnionType t, P p) {
 129         return visitUnknown(t, p);
 130     }
 131 
 132     /**
 133      * {@inheritDoc}
 134      *
 135      * @implSpec Visits an {@code IntersectionType} element by calling {@code
 136      * visitUnknown}.
 137      *
 138      * @param t  {@inheritDoc}
 139      * @param p  {@inheritDoc}
 140      * @return the result of {@code visitUnknown}
 141      *
 142      * @since 1.8
 143      */
 144     @Override
 145     public R visitIntersection(IntersectionType t, P p) {
 146         return visitUnknown(t, p);
 147     }
 148 
 149     /**
 150      * {@inheritDoc}
 151      *
 152      * @implSpec The default implementation of this method in {@code
 153      * AbstractTypeVisitor6} will always throw {@code
 154      * UnknownTypeException}.  This behavior is not required of a
 155      * subclass.
 156      *
 157      * @param t  {@inheritDoc}
 158      * @param p  {@inheritDoc}
 159      * @return a visitor-specified result
 160      * @throws UnknownTypeException
 161      *  a visitor implementation may optionally throw this exception
 162      */
 163     @Override
 164     public R visitUnknown(TypeMirror t, P p) {
 165         throw new UnknownTypeException(t, p);
 166     }
 167 }