Which statement about a Java identifier is true?

Which statement about a Java identifier is true?

• A. It must begin with a digit
• B. It is used to identify variables, methods, classes, modules, and other user-defined items
• C. It cannot include underscores
• D. It is always a reserved keyword

Answer: (B)

Identifiers in Java are the names you use for your own program items—variables, methods, classes, interfaces, packages, and, with the module system, module names as well. They serve as labels the compiler and runtime use to refer to those elements. An identifier must start with a letter, an underscore, or a dollar sign, and can be followed by letters, digits, underscores, or dollar signs. It cannot start with a digit and it cannot be a reserved keyword. So the statement that an identifier is used to identify variables, methods, classes, modules, and other user-defined items is the accurate description. It captures both the naming role of identifiers and the kinds of things programmers name with them. The other options miss important rules: identifiers may include underscores, they are not restricted to start with a digit, and identifiers are not themselves reserved keywords (keywords are reserved words that cannot be used as names).

Identifiers in Java are the names you use for your own program items—variables, methods, classes, interfaces, packages, and, with the module system, module names as well. They serve as labels the compiler and runtime use to refer to those elements. An identifier must start with a letter, an underscore, or a dollar sign, and can be followed by letters, digits, underscores, or dollar signs. It cannot start with a digit and it cannot be a reserved keyword.

So the statement that an identifier is used to identify variables, methods, classes, modules, and other user-defined items is the accurate description. It captures both the naming role of identifiers and the kinds of things programmers name with them. The other options miss important rules: identifiers may include underscores, they are not restricted to start with a digit, and identifiers are not themselves reserved keywords (keywords are reserved words that cannot be used as names).