hasNext() - when does it block and why?
java, java.util.scanner
Solution
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.
Problem
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 fine for many cases already, but now I have the case that's described in the JavaAPI as "MAY block and wait for Input". When does the `hasNext()` method block and how can I control it? The funny Thing is that it work's perfectly fine with 3 cases before the block. Also the JavaAPI describes `hasNext()` as the proper method for checking wether there is another Input or not so that the Method `next()` doesn't produce an `Exception`. Here is the code I did produce till now: ``` if (sc.hasNext() && sc.next().equals("create")) { if (sc.hasNextInt()) { width = sc.nextInt(); if (width > 0) { if (sc.hasNextInt()) { heigth = sc.nextInt(); if (heigth > 0) { if (sc.hasNext()) { //At this point the hasNext Statement blocks for //no reason till an Input is made. charset = sc.next(); Image = new AsciiImage(width, heigth,charset); } else { ret = false; System.out.println("INPUT MISMATCH"); } } ...//and so on ``` Thanks in advance, I couldn't find anything on this Topic an my own. Edit: The Scanner is defined as a System.in, but that shouldn't be a Problem - at least it hasn't been one till now.