2.1/user/src/com/google/gwt/dom/client/HeadingElement.java

/*
 * Copyright 2008 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.dom.client;

/**
 * For the H1 to H6 elements.
 * 
 * @see <a
 *      href="http://www.w3.org/TR/1999/REC-html401-19991224/struct/global.html#edef-H1">W3C
 *      HTML Specification</a>
 */
@TagName({HeadingElement.TAG_H1, HeadingElement.TAG_H2, HeadingElement.TAG_H3,
    HeadingElement.TAG_H4, HeadingElement.TAG_H5, HeadingElement.TAG_H6})
public class HeadingElement extends Element {

  static final String[] TAGS = {
      HeadingElement.TAG_H1, HeadingElement.TAG_H2, HeadingElement.TAG_H3,
      HeadingElement.TAG_H4, HeadingElement.TAG_H5, HeadingElement.TAG_H6};

  static final String TAG_H1 = "h1";
  static final String TAG_H2 = "h2";
  static final String TAG_H3 = "h3";
  static final String TAG_H4 = "h4";
  static final String TAG_H5 = "h5";
  static final String TAG_H6 = "h6";

  /**
   * Assert that the given {@link Element} is compatible with this class and
   * automatically typecast it.
   */
  public static HeadingElement as(Element elem) {
    if (HeadingElement.class.desiredAssertionStatus()) {
      // Assert that this element's tag name is one of [h1 .. h6].
      String tag = elem.getTagName().toLowerCase();
      assert tag.length() == 2;
      assert tag.charAt(0) == 'h';

      int n = Integer.parseInt(tag.substring(1, 2));
      assert (n >= 1) && (n <= 6);
    }

    return (HeadingElement) elem;
  }

  protected HeadingElement() {
  }
}