java identifiers

3.8 Identifiers

An identifier is an unlimited-length sequence of Java letters and Java digits, the

first of which must be a Java letter. An identifier cannot have the same spelling

(Unicode character sequence) as a keyword (§3.9), boolean literal (§3.10.3), or the null literal (§3.10.7).

A “Java letter” is a character for which the method Character.isJavaIden

tifierStart(int) returns true. A “Java letter-or-digit” is a character for which

the method Character.isJavaIdentifierPart(int) returns true.

The Java letters include uppercase and lowercase ASCII Latin letters A–Z

(\u0041–\u005a), and a–z (\u0061–\u007a), and, for historical reasons, the

ASCII underscore (_, or \u005f) and dollar sign ($, or \u0024). The $ character

should be used only in mechanically generated source code or, rarely, to access pre-existing names on legacy systems.

The “Java digits” include the ASCII digits 0-9 (\u0030–\u0039).

Two identifiers are the same only if they are identical, that is, have the same

Unicode character for each letter or digit.

Examples of identifiers are:

String i3 αρετη MAX_VALUE isLetterOrDigit