code: @Deprecated
      public static String getFileExtension(String filename) {
  
          int pos = filename.lastIndexOf('.');
          return (pos >= 0) ? filename.substring(pos).toLowerCase() : "";
      }
docs: Returns the extension of the given file name, that is the part behind the last '.' char,
  converted to lower case letters.<p>
  
  The result does contain the '.' char. For example, if the input is <code>"opencms.html"</code>,
  then the result will be <code>".html"</code>.<p>
  
  If the given file name does not contain a '.' char, the empty String <code>""</code> is returned.<p>
  
  Please note: No check is performed to ensure the given file name is not <code>null</code>.<p>
  
  @param filename the file name to get the extension for
  @return the extension of the given file name
  
  @deprecated use {@link #getExtension(String)} instead, it is better implemented