code: private static String openTag(String tag, String clazz, String style, boolean contentIsHtml, String... content) {
  		StringBuilder result = new StringBuilder("<").append(tag);
  		if (clazz != null && !"".equals(clazz)) {
  			result.append(" ").append(Html.Attribute.CLASS).append("='").append(clazz).append("'");
  		}
  		
  		if (style != null && !"".equals(style)) {
  			result.append(" ").append(Html.Attribute.STYLE).append("='").append(style).append("'");
  		}
  		result.append(">");
  		if (content != null && content.length > 0) {
  			for (String c : content) {
  				if (contentIsHtml) {
  					result.append(c);
  				} else {
  					result.append(htmlEncode(c));
  				}
  			}
  		}
  		return result.toString();
  	}
docs: Build a String containing a HTML opening tag with given CSS class and/or
  style and concatenates the given content.
  
  @param tag String name of HTML tag
  @param clazz CSS class of the tag
  @param style style for tag (plain CSS)
  @param contentIsHtml if false content is prepared with {@link HtmlBuilder#htmlEncode(String)}.
  @param content content string
  @return HTML tag element as string