CONSTRUCTOR

Constructor is a special method, that initializes an object immediately upon creation this automatic initialization is performed through the use of constructor.

KEY POINTS ABOUT CONSTRUCTOR:
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1. It should have same name as that of class.syantactically similar to a method
2. once defined and automatically called immediately after allocating memory
3. it does not have any return type.

TYPES OF CONSTRUCTOR:

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• Default Constructor:
• every class has its default constructor
• if default constructor is not provided then compiler creates its own& initializes the default value.
• no vales can be sent through default constructor
• Parameterized Constructor:
• Here values are set by specifically set as parameters.
• This is for various initializing values. 

PROGRAM:

~~~~~~~~~

public class room

{

int width ;

int length;

room( )                         // DEFAULT CONSTRUCTOR

{

width=5;

length=5;

}

room ( int w,int l)            //PARAMETERIZED CONSTRUCTOR

{

width=w;

length=l;

}

int area( )

{

return(width*length);

}

}

 class room1

 {

public static void main(String a[])

{

room r=new room( );

room r1=new room( 50,50);//passing parameters to the parameterized constructor

r.width=10;   //assigning values to the variables

r.length=20;

int result=r.area( );

System.out.println("AREA IS: "+result);// calling method from another class using object

System.out.println("AREA IS: "+r1.area( ));

}

}

OUTPUT:

~~~~~~~~

AREA IS: 200                //by default constructor

AREA IS: 2500             //by parameterized constructor