Variable Initializaion Declaration and Casting

How To Declare Variable :

Integer This group includes byte, short, int, long

  • byte : It is 8 bit (1 byte) integer data type. Value range from -128 to 127. Default value zero.
example: byte b=10;

  • short : It is 16 bit (2 byte) integer data type. Value range from -32768 to 32767. Default value zero.
example:short s=11;

  • int : It is 32 bit (4 byte) integer data type. Value range from -2147483648 to 2147483647. Default value zero.
example:int i=10;

  • long : It is 64 bit (8 byte) integer data type. Value range from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807. Default value zero.
example: long l=100012;

Floating-Point Number
This group includes float, double

  • float : It is 32 bit (4 byte) float data type. Default value 0.0f
example: float ff=10.3f;

  • double : It is 64 bit (8 byte) float data type. Default value 0.0d.
example: double db=11.123;

Characters
This group represent char, which represent symbols in a character set, like letters and numbers.

  • char : It is 16 bit (2 byte) unsigned unicode character. Range 0 to 65,535
example: char c='a';

Boolean
  • This group represent boolean, which is a special type for representing true/false values. They are defined constant of the language.
example: boolean b=true;

How to Initialize Variable :
Datatype VariableName = Value;
e.g :
int a=10;

Type Casting

Assigning a value of one type to a variable of another type is known as Type Casting.

Example :
int x = 10;
byte y = (byte)x;
In Java, type casting is classified into two types,

  • Widening Casting(Implicit)
  • Narrowing Casting(Explicitly done)

Widening or Automatic type conversion

Automatic Type casting takes place when,
  • The two types are compatible
  • The target type is larger than the source type

Example :



public class Test
{
    public static void main(String[] args)
    {
      int i = 100;	
      long l = i;	//no explicit type casting required  
      float f = l;	//no explicit type casting required  
      System.out.println("Int value "+i);
      System.out.println("Long value "+l);
      System.out.println("Float value "+f);
    }
    
}


Output :
Int value 100
Long value 100
Float value 100.0

Narrowing or Explicit type conversion