code: private static String stringValue(Object attributeValue) {
  
          if (attributeValue == null) {
              return (null);
          } else if (attributeValue instanceof String) {
              return ((String) attributeValue);
          } else {
              return (attributeValue.toString());
          }
  
      }
docs: <p>Return the specified attribute value, converted to a
  <code>String</code>.</p>
  
  @param attributeValue The attribute value to be converted