Tuesday, November 9, 2010

Legal Java Identifiers

Technically, legal identifiers must be composed of only Unicode characters,numbers, currency symbols, and connecting characters (like underscores).

  • Identifiers must start with a letter, a currency character ($), or a connecting character such as the underscore ( _ ). Identifiers cannot start with a number!
  • After the first character, identifiers can contain any combination of letters, currency characters, connecting characters, or numbers.
  • In practice, there is no limit to the number of characters an identifier can contain.
  • You can't use a Java keyword as an identifier. Below table lists all of the Java keywords including one new one for 5.0, enum.
  • Identifiers in Java are case-sensitive; foo and FOO are two different identifiers.
Examples of legal and illegal identifiers follow, first some legal identifiers:

  int _a;
  int $c;
  int ______2_w;
  int _$;
  int this_is_a_very_detailed_name_for_an_identifier;

The following are illegal:

  int :b;
  int -d;
  int e#;
  int .f;
  int 7g;

Complete List of Java Keywords (assert added in 1.4, enum added in 1.5)

abstractbooleanbreakbytecasecatch
charclassconstcontinuedefaultdo
doubleelseextendsfinalfinallyfloat
forgotoifimplementsimportinstanceof
intinterfacelongnativenewpackage
privateprotectedpublicreturnshortstatic
strictfpsuperswitchsynchronizedthisthrow
throwstransienttryvoidvolatilewhile
assertenum

1 comment:

  1. THE NO SPACE IN BETWEEN IS NOT INCLUDED.

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