/*
* Copyright (c) 2005, 2017, 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
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 visitXyz
method most applicable
* to that element is invoked.
*
*
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. * *
WARNING: 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. * *
Note that methods to accommodate new language constructs could
* be added in a source compatible way if they were added as
* default methods. 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 were required to
* also be runnable on Java SE 7. Therefore, default methods
* were not used when extending {@code javax.lang.model.*}
* to cover Java SE 8 language features. However, default methods
* are 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 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
*/
public interface ElementVisitor