Mercurial > jdk8-mips64-public > langtools / file revision

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 package javax.lang.model.util;

 import javax.lang.model.element.*;

 import javax.annotation.processing.SupportedSourceVersion;

 import javax.lang.model.SourceVersion;

 import static javax.lang.model.SourceVersion.*;

 /**

  * A scanning visitor of program elements with default behavior

  * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}

  * source version.  The <tt>visit<i>XYZ</i></tt> methods in this

  * class scan their component elements by calling {@code scan} on

  * their {@linkplain Element#getEnclosedElements enclosed elements},

  * {@linkplain ExecutableElement#getParameters parameters}, etc., as

  * indicated in the individual method specifications.  A subclass can

  * control the order elements are visited by overriding the

  * <tt>visit<i>XYZ</i></tt> methods.  Note that clients of a scanner

  * may get the desired behavior be invoking {@code v.scan(e, p)} rather

  * than {@code v.visit(e, p)} on the root objects of interest.

  *

  * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the

  * new method can cause the enclosed elements to be scanned in the

  * default way by calling <tt>super.visit<i>XYZ</i></tt>.  In this

  * fashion, the concrete visitor can control the ordering of traversal

  * over the component elements with respect to the additional

  * processing; for example, consistently calling

  * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden

  * methods will yield a preorder traversal, etc.  If the component

  * elements should be traversed in some other order, instead of

  * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method

  * should call {@code scan} with the elements in the desired order.

  *

  * <p> Methods in this class may be overridden subject to their

  * general contract.  Note that annotating methods in concrete

  * subclasses with {@link java.lang.Override @Override} will help

  * ensure that methods are overridden as intended.

  *

  * <p> <b>WARNING:</b> The {@code ElementVisitor} interface

  * implemented by this class may have methods added to it in the

  * future to accommodate new, currently unknown, language structures

  * added to future versions of the Java™ programming language.

  * Therefore, methods whose names begin with {@code "visit"} may be

  * added to this class in the future; to avoid incompatibilities,

  * classes which extend this class should not declare any instance

  * methods with names beginning with {@code "visit"}.

  *

  * <p>When such a new visit method is added, the default

  * implementation in this class will be to call the {@link

  * #visitUnknown visitUnknown} method.  A new element scanner visitor

  * class will also be introduced to correspond to the new language

  * level; this visitor will have different default behavior for the

  * visit method in question.  When the new visitor is introduced, all

  * or portions of this visitor may be deprecated.

  *

  * @param <R> the return type of this visitor's methods.  Use {@link

  *            Void} for visitors that do not need to return results.

  * @param <P> the type of the additional parameter to this visitor's

  *            methods.  Use {@code Void} for visitors that do not need an

  *            additional parameter.

  *

  * @author Joseph D. Darcy

  * @author Scott Seligman

  * @author Peter von der Ahé

  *

  * @see ElementScanner7

  * @see ElementScanner8

  * @since 1.6

  */

 @SupportedSourceVersion(RELEASE_6)

 public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {

     /**

      * The specified default value.

      */

     protected final R DEFAULT_VALUE;

     /**

      * Constructor for concrete subclasses; uses {@code null} for the

      * default value.

      */

     protected ElementScanner6(){

         DEFAULT_VALUE = null;

     }

     /**

      * Constructor for concrete subclasses; uses the argument for the

      * default value.

      */

     protected ElementScanner6(R defaultValue){

         DEFAULT_VALUE = defaultValue;

     }

     /**

      * Iterates over the given elements and calls {@link

      * #scan(Element, Object) scan(Element, P)} on each one.  Returns

      * the result of the last call to {@code scan} or {@code

      * DEFAULT_VALUE} for an empty iterable.

      *

      * @param iterable the elements to scan

      * @param  p additional parameter

      * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements

      */

     public final R scan(Iterable<? extends Element> iterable, P p) {

         R result = DEFAULT_VALUE;

         for(Element e : iterable)

             result = scan(e, p);

         return result;

     }

     /**

      * Processes an element by calling {@code e.accept(this, p)};

      * this method may be overridden by subclasses.

      *

      * @param e the element to scan

      * @param p a scanner-specified parameter

      * @return the result of visiting {@code e}.

      */

     public R scan(Element e, P p) {

         return e.accept(this, p);

     }

     /**

      * Convenience method equivalent to {@code v.scan(e, null)}.

      *

      * @param e the element to scan

      * @return the result of scanning {@code e}.

      */

     public final R scan(Element e) {

         return scan(e, null);

     }

     /**

      * {@inheritDoc} This implementation scans the enclosed elements.

      *

      * @param e  {@inheritDoc}

      * @param p  {@inheritDoc}

      * @return the result of scanning

      */

     public R visitPackage(PackageElement e, P p) {

         return scan(e.getEnclosedElements(), p);

     }

     /**

      * {@inheritDoc} This implementation scans the enclosed elements.

      *

      * @param e  {@inheritDoc}

      * @param p  {@inheritDoc}

      * @return the result of scanning

      */

     public R visitType(TypeElement e, P p) {

         return scan(e.getEnclosedElements(), p);

     }

     /**

      * {@inheritDoc}

      *

      * This implementation scans the enclosed elements, unless the

      * element is a {@code RESOURCE_VARIABLE} in which case {@code

      * visitUnknown} is called.

      *

      * @param e  {@inheritDoc}

      * @param p  {@inheritDoc}

      * @return the result of scanning

      */

     public R visitVariable(VariableElement e, P p) {

         if (e.getKind() != ElementKind.RESOURCE_VARIABLE)

             return scan(e.getEnclosedElements(), p);

         else

             return visitUnknown(e, p);

     }

     /**

      * {@inheritDoc} This implementation scans the parameters.

      *

      * @param e  {@inheritDoc}

      * @param p  {@inheritDoc}

      * @return the result of scanning

      */

     public R visitExecutable(ExecutableElement e, P p) {

         return scan(e.getParameters(), p);

     }

     /**

      * {@inheritDoc} This implementation scans the enclosed elements.

      *

      * @param e  {@inheritDoc}

      * @param p  {@inheritDoc}

      * @return the result of scanning

      */

     public R visitTypeParameter(TypeParameterElement e, P p) {

         return scan(e.getEnclosedElements(), p);

     }

 }