Custom Fields is not Updated Via Suitetalk

Hi

I am using Java for Suitetalk . when trying to update a cutomfield , nothing gets updated .

        CustomFieldRef ref = null;

         StringCustomFieldRef customField = new StringCustomFieldRef();



           customField.setInternalId("cust_field");         

           customField.setValue("some_value");

           CustomFieldRef[] updatedFields ;

           updatedFields= new CustomFieldRef[]{ref};

           CustomFieldList list = new CustomFieldList(updatedFields);

           record.setCustomFieldList(list);


no error is being thrown when calling the update/create record although the field is not getting updated.

note that when trying to do the same with an CustomRecord i get an error "customField Key is missing"

please help