Scanner - Only 1 Character

Question

The code below is from: Take a char input from the Scanner

char c = reader.next(".").charAt(0);

Why does this take in strictly one character? Any references where I can read about the purpose of the "."?

Answer 1

The character . reffers a Regular Expression (Regex) that means any character.

As you can find in the documentation of Pattern.

Predefined character classes

. Any character (may or may not match line terminators)

Regular Expression is a way to find, match text with some predefined Pattern. If you want to find the next A ou B letter, you should use:

char c = reader.next("[AB]").charAt(0);

Take a look at the Pattern documentation to learn better how to use this API.