Are all names identifiers?

Question

In the Java Language Specification 6.2 Link

Here is the following code example:

class Test {
    public static void main(String[] args) {
        Class c = System.out.getClass();
        System.out.println(c.toString().length() +
                           args[0].length() + args.length);
    }
}

And it states:

the identifiers Test, main, and the first occurrences of args and c are not names. Rather, they are used in declarations to specify the names of the declared entities. The names String, Class, System.out.getClass, System.out.println, c.toString, args, and args.length appear in the example.

But are the names like Class and String also identifiers? What is an identifier exactly?

Answer 1

An identifier is a type of a token. From the specification of the lexical structure of Java:

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.

Identifier:
    IdentifierChars but not a Keyword or BooleanLiteral or NullLiteral

IdentifierChars:
    JavaLetter
    IdentifierChars JavaLetterOrDigit

 JavaLetter:
     any Unicode character that is a Java letter (see below)

 JavaLetterOrDigit:
     any Unicode character that is a Java letter-or-digit (see below)

A "Java letter" is a character for which the method Character.isJavaIdentifierStart(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).

Letters and digits may be drawn from the entire Unicode character set, which supports most writing scripts in use in the world today, including the large sets for Chinese, Japanese, and Korean. This allows programmers to use identifiers in their programs that are written in their native languages.

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), or a compile-time error occurs.

Answer 2

An identifier is a user defined symbol.

It allows the compiler to differentiate between bindings to objects of the same type in the symbol table.

Answer 3

This might answer your 2nd question:

http://www.cafeaulait.org/course/week2/08.html

Identifiers are the names of variables, methods, classes, packages and interfaces. Unlike literals they are not the things themselves, just ways of referring to them.