Therefore, the Catalog Id value added in the input form is not valid. If the fetch() method returns a row, set the innerHTML of the validationMessage div to "Catalog Id is not Valid"

For method calls, I tried the same three access variations as for field access, with the added variable of using no-argument methods versus passing and returning a value on the method calls.

If we had added a getValue method to class Leaf, we would either have to return some sort of flag value indicating that the method application is non-sensical or actually throw an exception.