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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_9 RELEASE_9}

 * 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.

 *

 * @see ElementScanner6

 * @see ElementScanner7

 * @see ElementScanner8

 * @since 1.9

 */

@SupportedSourceVersion(RELEASE_9)

public class ElementScanner9<R, P> extends ElementScanner8<R, P> {

    /**

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

     * default value.

     */

    protected ElementScanner9(){

        super(null);

    }

    /**

     * Constructor for concrete subclasses; uses the argument for the

     * default value.

     *

     * @param defaultValue the default value

     */

    protected ElementScanner9(R defaultValue){

        super(defaultValue);

    }

}