Java Scanner with regex delimiter

Question

Why does the following code return false?

Scanner sc = new Scanner(\"-v \");
sc.useDelimiter(\"-[a-zA-Z]\\\\s+\");
System.out.println(sc.hasNext());

Answer 1

A scanner is used to break up a string into tokens. Delimiters are the separators between tokens. The delimiters are what aren't matched by the scanner; they're discarded. You're telling the scanner that -[a-zA-Z]\\s+ is a delimiter and since -v matches that regex it skips it.

If you're looking for a string that matches the regex, use String.matches().

If your goal really is to split a string into tokens then you might also consider String.split(), which is sometimes more convenient to use.