code: private boolean defineEntity(String name, char value)
      {
          StringBuffer sb = new StringBuffer("&");
          sb.append(name);
          sb.append(';');
          String entityString = sb.toString();
          
          boolean extra = defineChar2StringMapping(entityString, value);
          return extra;
      }
docs: Defines a new character reference. The reference's name and value are
  supplied. Nothing happens if the character reference is already defined.
  <p>Unlike internal entities, character references are a string to single
  character mapping. They are used to map non-ASCII characters both on
  parsing and printing, primarily for HTML documents. '&amp;lt;' is an
  example of a character reference.</p>
  
  @param name The entity's name
  @param value The entity's value
  @return true if the mapping is not one of:
  <ul>
  <li> '<' to "&lt;"
  <li> '>' to "&gt;"
  <li> '&' to "&amp;"
  <li> '"' to "&quot;"
  </ul>