hasNext() - when does it block and why?

Question

I\'m trying to read commands via a Scanner Object. For checking the Input Syntax I use sc.hasNext() (for the case of missing commands). It did work

Answer 1

There is a difference between testing via Console or via TextFile. If I read from Console the program expects a Stream and it will wait for further Input.

When testing via Input from Textfile (still with System.in for the Scanner, using Java Program ) the hasNext() will return false at the end of the file as no further Input can be done.

I can't really find documentation (in https://docs.oracle.com/javase/9/docs/api/java/util/Scanner.html#hasNext--) on this Topic. So if anyone finds a proper and technical correct answer I would be very greatfull.