Classes And Objects in java || Declaring Objects of Class || Assigning Object Reference Variables

 Classes And Objects:

Class is a template for an object, and an object is an instance of a class.

Syntax:

class className

{

type instance-variable1;

type instance-variable2;

type instance-variableN;

type methodname1(parameter-list)

{ // body of method }

type methodname2(parameter-list)

{ // body of method }

type methodnameN(parameter-list)

{ // body of method }

}

Example

class Rectangle

{

int height;

int width;

int Area()

{

return height*width;

}

}

Declaring Objects of Class:

Syntax:

className objName = new classNameOrConstructor();

Example:

Rectangle myRec = new Rectangle();

e.g. class Rectangle {

int height, width;

public static void main(String args[])

{ Rectangle myRec = new Rectangle();

myRec.height = 3;

myRec.width = 2;

System.out.println("Area of Rectangle :" + myRec.height*myRec.width); } }

Assigning Object Reference Variables:

When you assign one object reference variable to another object reference variable, you are not creating a copy of the object; you are only making a copy of the reference.

e.g. Rectangle myRec1 = new Rectangle();

Rectangle myRec2 = myRec1;

In above example both myRec1 and myRec2 are referring to a single object. myRec1 is not copied to myRec2 only its address.