Variable in Java is a data container that stores the data values during Java program execution. Every variable is assigned data type which designates the type and quantity of value it can hold. Variable is a memory location name of the data. The Java variables have mainly three types : Local, Instance and Static.
In order to use a variable in a program you to need to perform 2 steps
To declare a variable, you must specify the data type & give the variable a unique name.
Examples of other Valid Declarations are
int a,b,c;
float pi;
double d;
char a;
Variable Initialization:
To initialize a variable, you must assign it a valid value.
Example of other Valid Initializations are
pi =3.14f;
do =20.22d;
a=’v’;
You can combine variable declaration and initialization.
Primitive Data Types :- which include integer, character, boolean, and float
Non-primitive Data Types :- which include classes, arrays and interfaces.
Primitive Data Types are predefined and available within the Java language. Primitive values do not share state with other primitive values.
There are 8 primitive types: byte, short, int, long, char, float, double, and boolean Integer data types
byte (1 byte)
short (2 bytes)
int (4 bytes)
long (8 bytes)
char (2 bytes)
Logical
boolean (1 byte) (true/false)
Java Data Types
Data Type
Default Value
Default size
byte
0
1 byte
short
0
2 bytes
int
0
4 bytes
long
0L
8 bytes
float
0.0f
4 bytes
double
0.0d
8 bytes
boolean
false
1 bit
char
'\u0000'
2 bytes
Points to Remember:
All numeric data types are signed(+/-).
The size of data types remain the same on all platforms (standardized)
char data type in Java is 2 bytes because it uses UNICODE character set. By virtue of it, Java supports internationalization. UNICODE is a character set which covers all known scripts and language in the world
Java Variable Type Conversion & Type Casting
A variable of one type can receive the value of another type. Here there are 2 cases -
Case 1) Variable of smaller capacity is be assigned to another variable of bigger capacity. This process is Automatic, and non-explicit is known as Conversion
Case 2) Variable of larger capacity is be assigned to another variable of smaller capacity
