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

 /*

  * Copyright (c) 2005, 2013, Oracle and/or its affiliates. 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.  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.element;

 import javax.lang.model.util.*;

 /**

  * A visitor of program elements, in the style of the visitor design

  * pattern.  Classes implementing this interface are used to operate

  * on an element when the kind of element is unknown at compile time.

  * When a visitor is passed to an element's {@link Element#accept

  * accept} method, the <tt>visit<i>XYZ</i></tt> method most applicable

  * to that element is invoked.

  *

  * <p> Classes implementing this interface may or may not throw a

  * {@code NullPointerException} if the additional parameter {@code p}

  * is {@code null}; see documentation of the implementing class for

  * details.

  *

  * <p> <b>WARNING:</b> It is possible that methods will be added to

  * this interface to accommodate new, currently unknown, language

  * structures added to future versions of the Java™ programming

  * language.  Therefore, visitor classes directly implementing this

  * interface may be source incompatible with future versions of the

  * platform.  To avoid this source incompatibility, visitor

  * implementations are encouraged to instead extend the appropriate

  * abstract visitor class that implements this interface.  However, an

  * API should generally use this visitor interface as the type for

  * parameters, return type, etc. rather than one of the abstract

  * classes.

  *

  * <p>Note that methods to accommodate new language constructs could

  * be added in a source <em>compatible</em> way if they were added as

  * <em>default methods</em>.  However, default methods are only

  * available on Java SE 8 and higher releases and the {@code

  * javax.lang.model.*} packages bundled in Java SE 8 are required to

  * also be runnable on Java SE 7.  Therefore, default methods

  * <em>cannot</em> be used when extending {@code javax.lang.model.*}

  * to cover Java SE 8 language features.  However, default methods may

  * be used in subsequent revisions of the {@code javax.lang.model.*}

  * packages that are only required to run on Java SE 8 and higher

  * platform versions.

  *

  * @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 AbstractElementVisitor6

  * @see AbstractElementVisitor7

  * @since 1.6

  */

 public interface ElementVisitor<R, P> {

     /**

      * Visits an element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visit(Element e, P p);

     /**

      * A convenience method equivalent to {@code v.visit(e, null)}.

      * @param e  the element to visit

      * @return a visitor-specified result

      */

     R visit(Element e);

     /**

      * Visits a package element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visitPackage(PackageElement e, P p);

     /**

      * Visits a type element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visitType(TypeElement e, P p);

     /**

      * Visits a variable element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visitVariable(VariableElement e, P p);

     /**

      * Visits an executable element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visitExecutable(ExecutableElement e, P p);

     /**

      * Visits a type parameter element.

      * @param e  the element to visit

      * @param p  a visitor-specified parameter

      * @return a visitor-specified result

      */

     R visitTypeParameter(TypeParameterElement e, P p);

     /**

      * Visits an unknown kind of element.

      * This can occur if the language evolves and new kinds

      * of elements are added to the {@code Element} hierarchy.

      *

      * @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

      */

     R visitUnknown(Element e, P p);

 }