Conditions of using the list method in the file class

After a directory is specified, you want to use the list method to list all file names in the directory. If there are no files in the directory, subsequent operations are not allowed. At first, I mistakenly thought that the list method would return a null value when there is no file in the path. As a result, no correct result is obtained according to this idea, the output return value indicates that no file value in the path is null. After viewing the help documentation, I learned that a null value is returned only when the given string does not represent a path or an input/output error occurs. Therefore, the objective is to determine the length of the returned value (String Array.