Identifiers
are the names of variables, methods, classes, packages and
interfaces. Identifiers must be composed of letters, numbers, the
underscore _ and the dollar sign $
Some
Rules of Identifier Naming Convention in Java:
- Variable names are case-sensitive.
- A variable’s name can be any legal identifier.
- It can contain Unicode letter,Digits and Two Special Characters such as Underscore and dollar Sign.
- Length of Variable name can be any number.
- Its necessary to use Alphabet at the start (however we can use underscore , but do not use it )
- Some auto generated variables may contain ‘$‘ sign. But try to avoid using Dollar Sign.
- White space is not permitted.
- Special Characters are not allowed.
- Digit at start is not allowed
- Subsequent characters may be letters, digits, dollar signs, or underscore characters.
- Variable name must not be a keyword or reserved word.
The
following are not legal variable names:
My
Variable // Contains a space
9pins
// Begins with a digit
a+c
// The plus sign is not an alphanumeric character
testing1-2-3
// The hyphen is not an alphanumeric character
O'Reilly
// Apostrophe is not an alphanumeric character
OReilly_&_Associates
// ampersand is not an alphanumeric character
Some Standard Conventions Used :
1. Never Use Dollar Or Underscore as First Letter
- Dollar Sign and Underscore as First Character in Variable name is allowed but still its not good programming Style to use it as First Character.
- Generally we use Underscore in “Constant Value” variable.
static final int TOTAL_NUM = 10; static final int MAX_COUNT = 20;
*Final
is nothing but constant value in Java (In c we use const)
2. Capitalization of First Character of Second Word
- If variable name contain two words then write first letter of second word in Capital Case.
- If variable name contain single word then write that word in small case.
Example : Multiple Words in Variable Name
sumOfNumber firstNumber skinColor
Example : Single Word in Variable Name
sum first last
