/* * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright *    notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright *    notice, this list of conditions and the following disclaimer in *    the documentation and/or other materials provided with the *    distribution. * * 3. The end-user documentation included with the redistribution, *    if any, must include the following acknowledgment: *       "This product includes software developed by the *       Sun Microsystems, Inc. for Project JXTA." *    Alternately, this acknowledgment may appear in the software itself, *    if and wherever such third-party acknowledgments normally appear. * * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"  *    must not be used to endorse or promote products derived from this *    software without prior written permission. For written *    permission, please contact Project JXTA at http://www.jxta.org. * * 5. Products derived from this software may not be called "JXTA", *    nor may "JXTA" appear in their name, without prior written *    permission of Sun. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of Project JXTA.  For more * information on Project JXTA, please see * <http://www.jxta.org/>. * * This license is based on the BSD license adopted by the Apache Foundation. * * $Id: Element.java,v 1.16 2003/05/13 19:35:34 bondolo Exp $ */package net.jxta.document;import java.util.Enumeration;/** *  An element represents a portion of a {@link StructuredDocument}. An element *  is identifiable by a <code>key</code> and may also optionally have a *  <code>value</code>. Each Element also maintains a collection of references *  to other elements, its <emphasis>children</emphasis>. Elmenents can be *  composed into arbitrary hierarchical structures forming complex data *  structures. * *  <p/>Element instances are always associated with a *  {@link StructuredDocument}. A {@link StructuredDocument} is a specialized *  form of Element with additional features that make it appropriate for *  acting as the root of a hierarchy of elements. * *  @see net.jxta.document.Document *  @see net.jxta.document.StructuredDocument *  @see net.jxta.document.StructuredDocumentFactory *  @see net.jxta.document.StructuredTextDocument *  @see net.jxta.document.TextElement **/public interface Element {        /**     * Get the key associated with this Element.     *     * @return Object The key of this Element.     **/    Object getKey();        /**     * Get the value (if any) associated with this Element.     *     * @return Object The value of this element, if any, otherwise null.     **/    Object getValue();        /**     *  Get the root Element of the hierarchy this Element belongs to.     *     *  @return StructuredDocument The root element of this element's hierarchy.     **/    StructuredDocument getRoot();        /**     * Get the parent element of this element. If this Element has not been     * inserted into the Document then <code>null</code> is returned. If this     * element is the root element of the Document then it returns itself. ie.,     * <code>this == this.getParent()</code>.     *     * @return Element parent of this element. If the element has no parent     * then null will be returned. If the element is the root Element of the     * hierarchy then it will return itself.     **/    Element getParent();        /**     *  Add a child element to this element. The child element must be from the     *  document as the element it is to be added to.     *     *  @param element the element to be added as a child     **/    void appendChild( Element element );        /**     *  Returns an enumeration of the immediate children of this element.     *     *  @return Enumeration An enumeration containing all of the children of     *  this element.     **/    Enumeration getChildren();        /**     *  Returns an enumeration of the immediate children of this element whose     *  name match the specified key.     *     *  @param key The key which will be matched against.     *  @return Enumeration enumeration containing all of the children of this     *  element.     **/    Enumeration getChildren( Object key );}