Java Language Lexicon: Whitespace, Identifiers, Keywords & Comments - Quiz
Total: 2 questions
1. Which characters can a Java identifier start with?
Which characters can a Java identifier start with?
An identifier must start with a letter, a currency character such as $, or a connecting character such as the underscore _. It cannot start with a digit: 6j and 5g do not compile, while _n, $p and name do. Since Java 9 a single underscore _ on its own is a keyword and cannot be used as an identifier.
2. Which characters can a Java identifier contain after the first character?
Which characters can a Java identifier contain after the first character?
After the first character an identifier may contain any combination of letters, digits, currency characters ($) and connecting characters (_). Spaces and other symbols such as #, ., : or - are not allowed, so my-temp and j# are illegal. There is no length limit, identifiers are case-sensitive (count and Count are different names), and a keyword such as class cannot be an identifier.