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byte extends int short true
case false interface static try
catch final long strictfp void
char finally native super volatile
class float new switch while
const for null synchronized continue
default goto package private this
abstract do if
Note: The "const" and "goto" keywords are not used in Java, but they are reserved for potential future
use.
4.4.2 Identifiers
In Java, identifiers are used to represent user-defined names, such as the names of variables, methods, classes, and
other user-defined entities. An identifier can be a combination of letters, digits, underscores (_), and dollar signs ($). It
must start with a letter (either lowercase or uppercase), an underscore (_), or a dollar sign ($). However, an identifier
cannot start with a digit. You cannot use Java keywords as identifiers. Keywords are reserved for special use in the
language. Identifiers must be unique, and if two identifiers differ only by case (e.g., age and AGE), they are considered
different. After an identifier is declared, it can be used throughout the program to refer to the associated value.
Identifier Naming Conventions
Following are some protocols that are followed while naming the identifiers:
• An identifier must start with a letter (a–z or A–Z) or underscore (_) or dollar ($).
• An identifier can not start with a digit. However, apart from the first character, it can have any combination of
letters or digits.
• An identifier is case sensitive which means “AGE” and “age” are two different identifiers.
• An identifier can be of any length.
• An identifier cannot contain whitespaces.
• An identifier cannot be a Java keyword.
• An identifier must not contain any type of special symbol apart from $ and _.
Examples of valid Identifiers:
Name, $add, _cost, marks_computer, country_91, etc.
Examples of invalid Identifiers:
1. 91_country - cannot start with number.
2. cost price - cannot contain space within.
3. s+p - cannot contain any type of special symbol apart from $ and _.
4. class - cannot use any keyword.
Definition
Identifiers are the names given to different components of a Java program like class, variables
and methods.
62 Touchpad Computer Applications-IX
Literals

