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.lang.model.element.*;
  29 import javax.annotation.processing.SupportedSourceVersion;
  30 import javax.lang.model.SourceVersion;
  31 import static javax.lang.model.SourceVersion.*;
  32 
  33 
  34 /**
  35  * A scanning visitor of program elements with default behavior
  36  * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
  37  * source version.  The <code>visit<i>Xyz</i></code> methods in this
  38  * class scan their component elements by calling {@code scan} on
  39  * their {@linkplain Element#getEnclosedElements enclosed elements},
  40  * {@linkplain ExecutableElement#getParameters parameters}, etc., as
  41  * indicated in the individual method specifications.  A subclass can
  42  * control the order elements are visited by overriding the
  43  * <code>visit<i>Xyz</i></code> methods.  Note that clients of a scanner
  44  * may get the desired behavior be invoking {@code v.scan(e, p)} rather
  45  * than {@code v.visit(e, p)} on the root objects of interest.
  46  *
  47  * <p>When a subclass overrides a <code>visit<i>Xyz</i></code> method, the
  48  * new method can cause the enclosed elements to be scanned in the
  49  * default way by calling <code>super.visit<i>Xyz</i></code>.  In this
  50  * fashion, the concrete visitor can control the ordering of traversal
  51  * over the component elements with respect to the additional
  52  * processing; for example, consistently calling
  53  * <code>super.visit<i>Xyz</i></code> at the start of the overridden
  54  * methods will yield a preorder traversal, etc.  If the component
  55  * elements should be traversed in some other order, instead of
  56  * calling <code>super.visit<i>Xyz</i></code>, an overriding visit method
  57  * should call {@code scan} with the elements in the desired order.
  58  *
  59  * <p> Methods in this class may be overridden subject to their
  60  * general contract.  Note that annotating methods in concrete
  61  * subclasses with {@link java.lang.Override @Override} will help
  62  * ensure that methods are overridden as intended.
  63  *
  64  * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
  65  * implemented by this class may have methods added to it in the
  66  * future to accommodate new, currently unknown, language structures
  67  * added to future versions of the Java&trade; programming language.
  68  * Therefore, methods whose names begin with {@code "visit"} may be
  69  * added to this class in the future; to avoid incompatibilities,
  70  * classes which extend this class should not declare any instance
  71  * methods with names beginning with {@code "visit"}.
  72  *
  73  * <p>When such a new visit method is added, the default
  74  * implementation in this class will be to call the {@link
  75  * #visitUnknown visitUnknown} method.  A new element scanner visitor
  76  * class will also be introduced to correspond to the new language
  77  * level; this visitor will have different default behavior for the
  78  * visit method in question.  When the new visitor is introduced, all
  79  * or portions of this visitor may be deprecated.
  80  *
  81  * @param <R> the return type of this visitor's methods.  Use {@link
  82  *            Void} for visitors that do not need to return results.
  83  * @param <P> the type of the additional parameter to this visitor's
  84  *            methods.  Use {@code Void} for visitors that do not need an
  85  *            additional parameter.
  86  *
  87  * @author Joseph D. Darcy
  88  * @author Scott Seligman
  89  * @author Peter von der Ah&eacute;
  90  *
  91  * @see ElementScanner7
  92  * @see ElementScanner8
  93  * @see ElementScanner9
  94  * @since 1.6
  95  * @deprecated Release 6 is obsolete; update to a visitor for a newer
  96  * release level.
  97  */
  98 @Deprecated
  99 @SupportedSourceVersion(RELEASE_6)
 100 public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {
 101     /**
 102      * The specified default value.
 103      */
 104     protected final R DEFAULT_VALUE;
 105 
 106     /**
 107      * Constructor for concrete subclasses; uses {@code null} for the
 108      * default value.
 109      */
 110     protected ElementScanner6(){
 111         DEFAULT_VALUE = null;
 112     }
 113 
 114     /**
 115      * Constructor for concrete subclasses; uses the argument for the
 116      * default value.
 117      *
 118      * @param defaultValue the default value
 119      */
 120     protected ElementScanner6(R defaultValue){
 121         DEFAULT_VALUE = defaultValue;
 122     }
 123 
 124     /**
 125      * Iterates over the given elements and calls {@link
 126      * #scan(Element, Object) scan(Element, P)} on each one.  Returns
 127      * the result of the last call to {@code scan} or {@code
 128      * DEFAULT_VALUE} for an empty iterable.
 129      *
 130      * @param iterable the elements to scan
 131      * @param  p additional parameter
 132      * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements
 133      */
 134     public final R scan(Iterable<? extends Element> iterable, P p) {
 135         R result = DEFAULT_VALUE;
 136         for(Element e : iterable)
 137             result = scan(e, p);
 138         return result;
 139     }
 140 
 141     /**
 142      * Processes an element by calling {@code e.accept(this, p)};
 143      * this method may be overridden by subclasses.
 144      *
 145      * @param e the element to scan
 146      * @param p a scanner-specified parameter
 147      * @return the result of visiting {@code e}.
 148      */
 149     public R scan(Element e, P p) {
 150         return e.accept(this, p);
 151     }
 152 
 153     /**
 154      * Convenience method equivalent to {@code v.scan(e, null)}.
 155      *
 156      * @param e the element to scan
 157      * @return the result of scanning {@code e}.
 158      */
 159     public final R scan(Element e) {
 160         return scan(e, null);
 161     }
 162 
 163     /**
 164      * {@inheritDoc} This implementation scans the enclosed elements.
 165      *
 166      * @param e  {@inheritDoc}
 167      * @param p  {@inheritDoc}
 168      * @return the result of scanning
 169      */
 170     public R visitPackage(PackageElement e, P p) {
 171         return scan(e.getEnclosedElements(), p);
 172     }
 173 
 174     /**
 175      * {@inheritDoc} This implementation scans the enclosed elements.
 176      *
 177      * @param e  {@inheritDoc}
 178      * @param p  {@inheritDoc}
 179      * @return the result of scanning
 180      */
 181     public R visitType(TypeElement e, P p) {
 182         return scan(e.getEnclosedElements(), p);
 183     }
 184 
 185     /**
 186      * {@inheritDoc}
 187      *
 188      * This implementation scans the enclosed elements, unless the
 189      * element is a {@code RESOURCE_VARIABLE} in which case {@code
 190      * visitUnknown} is called.
 191      *
 192      * @param e  {@inheritDoc}
 193      * @param p  {@inheritDoc}
 194      * @return the result of scanning
 195      */
 196     public R visitVariable(VariableElement e, P p) {
 197         if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
 198             return scan(e.getEnclosedElements(), p);
 199         else
 200             return visitUnknown(e, p);
 201     }
 202 
 203     /**
 204      * {@inheritDoc} This implementation scans the parameters.
 205      *
 206      * @param e  {@inheritDoc}
 207      * @param p  {@inheritDoc}
 208      * @return the result of scanning
 209      */
 210     public R visitExecutable(ExecutableElement e, P p) {
 211         return scan(e.getParameters(), p);
 212     }
 213 
 214     /**
 215      * {@inheritDoc} This implementation scans the enclosed elements.
 216      *
 217      * @param e  {@inheritDoc}
 218      * @param p  {@inheritDoc}
 219      * @return the result of scanning
 220      */
 221     public R visitTypeParameter(TypeParameterElement e, P p) {
 222         return scan(e.getEnclosedElements(), p);
 223     }
 224 }