/* * Copyright (c) 2005, 2014, 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 are required to
* also be runnable on Java SE 7. Therefore, default methods
* cannot 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 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