Identifiers in Java

Identifiers are names of classes, interfaces, methods, variables and packages.

 

Must start with:

• A - Z or a - z                     
• $  or _ (underscore)

Can also contain:

• 0-9

Cannot be 

• null literal
• boolean literal (true or false)
• a keyword

No limits on number of characters.

 

List of keywords:

 

 

Note: goto and const are reserved keywords in Java. (They are not used anywhere).

 

Examples:

 

Legal identifiers:

 

MyClass (Class name)

m1 (Method name)

var (Variable name)

_123 (Not recommended but legal)

$UNLIMITED (Strange)

MAX_VALUE (static final variable)

 

Illegal identifiers

 

public (keyword)

123_ (starts with number)

null (null literal)