Java: Variables
A variable can be thought of as a container which holds a value for you during the life of your program.
Every variable must be assigned a data type. That designates the type and quantity of a value it can hold.
Data Types:
Integer data types
- byte (1 byte)
- short (2 bytes)
- int (4 bytes)
- long (8 bytes)
Floating Data type
- float (4 bytes)
- double (8 bytes)
All numeric data types are signed(+/-).
The size of data types remain the same on all platforms (standardized)
Textual Data Type
The char data type in Java is 2 bytes because it uses the UNICODE character set. In this way, Java supports internationalization. The UNICODE is a character set which covers all known scripts and language in the world
Logical Data Types
- boolean (1 byte) (true/false)
Using a variable in a program:
You need to perform 2 steps:
To declare a variable , you must specify the data type and 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.
Example:
- int a=2,b=4,c=6;
- float pi=3.14f;
- double do=20.22d;
- char a='v';
Variable Type Conversion & Type Casting
A variable of one type can receive the value of another type.
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.
In such cases you have to explicitly specify the type cast operator. This process is know as Type Casting.
In case 1, as you do not specify a type cast operator, the compiler gives an error. Since this rule is enforced by the compiler , it makes the programmer aware that the conversion he is about to do may cause some loss in data and prevents accidental losses.
