Variables in Java: Definition and Usage Explained

Variables in java

Variable is name of reserved area allocated in memory. In other words, it is a name of memory location. Variables are used to store information to be referenced and manipulated in a computer program. value of the variable can change, depending on conditions or on information passed to the program. variable="vary + able" that means its value can be changed.

It is helpful to think of variables as containers that hold information.

Each variable in Java has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

You must declare all variables before they can be used. Following is the basic form of a variable declaration

Variable Declaration and Initialization in two step;

data_type variable_name ;
variable_name = Constant_value ;

int age ;
age = 21 ;

Here,

data_type is int

variable_name is age and

Constant_value 21

Variable Declaration and Initialization in one step

data_type variable_name = Constant_value ;

int age = 21 ;

Here,

data_type is int

variable_name is age and

Constant_value 21

A variable name can be chosen by the programmer in a meaningful way so as to reflect what it represents in the program. some Examples of variable name;

• average
• height
• classStrength
• roll
• semester
• averageLength
• etc.

Variable may consist of alphabets, digits, underscore(_), and dollar sign;

Rules for naming variables:

• All variable names must begin with a letter of the alphabet, an underscore, or ( _ ), or a dollar sign ($). The convention is to always use a letter of the alphabet. The dollar sign and the underscore are discouraged.
• Digit at start is not allowed.
• A variable’s name can be any legal identifier.
• After the first initial letter, variable names may also contain letters and the digits 0 to 9. No spaces or special characters are allowed.
• The name can be of any length, but don't get carried away. Remember that you will have to type this name.
• Uppercase characters are distinct from lowercase characters. Using ALL uppercase letters are primarily used to identify constant variables. Remember that variable names are case-sensitive.
• You cannot use a java keyword (reserved word) for a variable name.
• White space is not permitted.

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_SUM = 10;

static final int MAX_HEIGHT = 20;

*Final is nothing but constant value in Java (In C programming 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

firstRollno

skinColor

Example : Single Word in Variable Name

sum

first

last