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.type.*;
  29 import javax.annotation.processing.SupportedSourceVersion;
  30 import static javax.lang.model.SourceVersion.*;
  31 import javax.lang.model.SourceVersion;
  32 
  33 /**
  34  * A visitor of types based on their {@linkplain TypeKind kind} with
  35  * default behavior appropriate for the {@link SourceVersion#RELEASE_7
  36  * RELEASE_7} source version.  For {@linkplain
  37  * TypeMirror types} <code><i>XYZ</i></code> that may have more than one
  38  * kind, the <code>visit<i>XYZ</i></code> methods in this class delegate
  39  * to the <code>visit<i>XYZKind</i></code> method corresponding to the
  40  * first argument's kind.  The <code>visit<i>XYZKind</i></code> methods
  41  * call {@link #defaultAction defaultAction}, passing their arguments
  42  * to {@code defaultAction}'s corresponding parameters.
  43  *
  44  * <p> Methods in this class may be overridden subject to their
  45  * general contract.  Note that annotating methods in concrete
  46  * subclasses with {@link java.lang.Override @Override} will help
  47  * ensure that methods are overridden as intended.
  48  *
  49  * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented
  50  * by this class may have methods added to it in the future to
  51  * accommodate new, currently unknown, language structures added to
  52  * future versions of the Java&trade; programming language.
  53  * Therefore, methods whose names begin with {@code "visit"} may be
  54  * added to this class in the future; to avoid incompatibilities,
  55  * classes which extend this class should not declare any instance
  56  * methods with names beginning with {@code "visit"}.
  57  *
  58  * <p>When such a new visit method is added, the default
  59  * implementation in this class will be to call the {@link
  60  * #visitUnknown visitUnknown} method.  A new type kind visitor class
  61  * will also be introduced to correspond to the new language level;
  62  * this visitor will have different default behavior for the visit
  63  * method in question.  When the new visitor is introduced, all or
  64  * portions of this visitor may be deprecated.
  65  *
  66  * <p>Note that adding a default implementation of a new visit method
  67  * in a visitor class will occur instead of adding a <em>default
  68  * method</em> directly in the visitor interface since a Java SE 8
  69  * language feature cannot be used to this version of the API since
  70  * this version is required to be runnable on Java SE 7
  71  * implementations.  Future versions of the API that are only required
  72  * to run on Java SE 8 and later may take advantage of default methods
  73  * in this situation.
  74  *
  75  * @param <R> the return type of this visitor's methods.  Use {@link
  76  *            Void} for visitors that do not need to return results.
  77  * @param <P> the type of the additional parameter to this visitor's
  78  *            methods.  Use {@code Void} for visitors that do not need an
  79  *            additional parameter.
  80  *
  81  * @see TypeKindVisitor6
  82  * @see TypeKindVisitor8
  83  * @since 1.7
  84  */
  85 @SupportedSourceVersion(RELEASE_7)
  86 public class TypeKindVisitor7<R, P> extends TypeKindVisitor6<R, P> {
  87     /**
  88      * Constructor for concrete subclasses to call; uses {@code null}
  89      * for the default value.
  90      */
  91     @SuppressWarnings("deprecation") // Superclass constructor deprecated
  92     protected TypeKindVisitor7() {
  93         super(null);
  94     }
  95 
  96     /**
  97      * Constructor for concrete subclasses to call; uses the argument
  98      * for the default value.
  99      *
 100      * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
 101      */
 102     @SuppressWarnings("deprecation") // Superclass constructor deprecated
 103     protected TypeKindVisitor7(R defaultValue) {
 104         super(defaultValue);
 105     }
 106 
 107     /**
 108      * This implementation visits a {@code UnionType} by calling
 109      * {@code defaultAction}.
 110      *
 111      * @param t  {@inheritDoc}
 112      * @param p  {@inheritDoc}
 113      * @return the result of {@code defaultAction}
 114      */
 115     @Override
 116     public R visitUnion(UnionType t, P p) {
 117         return defaultAction(t, p);
 118     }
 119 }