code: @Nullable
    public String getCharSet ()
    {
      // Parameter parser can handle null input
      final ICommonsMap <String, String> aParams = new ParameterParser ().setLowerCaseNames (true)
                                                                         .parse (getContentType (), ';');
      return aParams.get ("charset");
    }
docs: Returns the content charset passed by the agent or <code>null</code> if not
  defined.
  
  @return The content charset passed by the agent or <code>null</code> if not
  defined.