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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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/*

 * Copyright (c) 2015 World Wide Web Consortium,

 *

 * (Massachusetts Institute of Technology, European Research Consortium for

 * Informatics and Mathematics, Keio University, Beihang). All Rights Reserved.

 * This work is distributed under the W3C(r) Software License [1] 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.

 *

 * [1] http://www.w3.org/Consortium/Legal/copyright-software

 */

package org.w3c.dom;

/**

 * The {@code ElementTraversal} interface is a set of read-only attributes

 * which allow an author to easily navigate between elements in a document.

 * <p>

 * In conforming implementations of Element Traversal, all objects that

 * implement {@link Element} must also implement the {@code ElementTraversal}

 * interface. Four of the methods,

 * {@link #getFirstElementChild}, {@link #getLastElementChild},

 * {@link #getPreviousElementSibling}, and {@link #getNextElementSibling},

 * each provides a live reference to another element with the defined

 * relationship to the current element, if the related element exists. The

 * fifth method, {@link #getChildElementCount}, exposes the number of child

 * elements of an element, for preprocessing before navigation.

 *

 * @see

 * <a href='http://www.w3.org/TR/ElementTraversal/'><cite>Element Traversal Specification</cite></a>.

 *

 * @since 9

 */

public interface ElementTraversal {

    /**

     * Returns a reference to the first child node of the element which is of

     * the {@link Element} type.

     *

     * @return a reference to an element child, {@code null} if the element has

     * no child of the {@link Element} type.

     */

    Element getFirstElementChild();

    /**

     * Returns a reference to the last child node of the element which is of

     * the {@link Element} type.

     *

     * @return a reference to an element child, {@code null} if the element has

     * no child of the {@link Element} type.

     */

    Element getLastElementChild();

    /**

     * Returns a reference to the sibling node of the element which most immediately

     * precedes the element in document order, and which is of the {@link Element} type.

     *

     * @return a reference to an element child, {@code null} if the element has

     * no sibling node of the {@link Element} type that comes before this one.

     */

    Element getPreviousElementSibling();

    /**

     * Returns a reference to the sibling node of the element which most immediately

     * follows the element in document order, and which is of the {@link Element} type.

     *

     * @return a reference to an element child, {@code null} if the element has

     * no sibling node of the {@link Element} type that comes after this one.

     */

    Element getNextElementSibling();

    /**

     * Returns the current number of child nodes of the element which are of

     * the {@link Element} type.

     *

     * @return the number of element children, or {@code 0} if the element has

     * no element children.

     */

    int getChildElementCount();

}