/*

 * Copyright 2005-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * 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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package javax.lang.model.util;

import javax.lang.model.element.*;

import javax.annotation.processing.SupportedSourceVersion;

import javax.lang.model.element.*;

import static javax.lang.model.element.ElementKind.*;

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

import javax.lang.model.SourceVersion;

/**

 * A skeletal visitor of program elements with default behavior

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

 * source version.

 *

 * <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 abstract element 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

 * @since 1.6

 */

@SupportedSourceVersion(RELEASE_6)

public abstract class AbstractElementVisitor6<R, P> implements ElementVisitor<R, P> {

    /**

     * Constructor for concrete subclasses to call.

     */

    protected AbstractElementVisitor6(){}

    /**

     * Visits any program element as if by passing itself to that

     * element's {@link Element#accept accept} method.  The invocation

     * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,

     * p)}.

     *

     * @param e  the element to visit

     * @param p  a visitor-specified parameter

     * @return a visitor-specified result

     */

    public final R visit(Element e, P p) {

        return e.accept(this, p);

    }

    /**

     * Visits any program element as if by passing itself to that

     * element's {@link Element#accept accept} method and passing

     * {@code null} for the additional parameter.  The invocation

     * {@code v.visit(elem)} is equivalent to {@code elem.accept(v,

     * null)}.

     *

     * @param e  the element to visit

     * @return a visitor-specified result

     */

    public final R visit(Element e) {

        return e.accept(this, null);

    }

    /**

     * {@inheritDoc}

     *

     * <p> The default implementation of this method in

     * {@code AbstractElementVisitor6} will always throw

     * {@code UnknownElementException}.

     * This behavior is not required of a subclass.

     *

     * @param e  the element to visit

     * @param p  a visitor-specified parameter

     * @return a visitor-specified result

     * @throws UnknownElementException

     *          a visitor implementation may optionally throw this exception

     */

    public R visitUnknown(Element e, P p) {

        throw new UnknownElementException(e, p);

    }

}