code: public String getNextStringParam(String strName)
      {
          String string = this.getProperty(strName);
          if (NULL.equals(string))
              string = null;
          return string;
      }
docs: Get the next (String) param.
  Typically this is overidden in the concrete implementation.
  @param strName The param name (in most implementations this is optional).
  @return The next param as a string.