Variable Initialization, Declaration and Casting

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;

Datatype VariableName = Value;
example: int a=10;

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 (Implicitly done)
Narrowing Casting (Explicitly done)

Automatic Type casting takes place when,

The two types are compatible.
The target type is larger than the source type.

Example

package com.javabykiran.variablesdemo;

public class JbkTest {
    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

Variable Initialization, Declaration and Casting

Syntax of Variable Declaration

How to Declare Variable?

How to Initialize Variable?

Type Casting

Widening or Automatic type conversion