Data Class , Object Declaration and Companion Object

Data class :-

Contain method such hashcode(), equal(), to String() ,copy()- BuiltIn

In data class, primary constructor contain variable(properties)

fun main(Args : Array<String>)

{

var user1 = user("sum",10)

var user2 = user("sum",10)

println(user1.toString())    //using inbuilt function of the data class (print everything!!) 

if(user1 == user2)

println("equals")

else

println("not equals")

var newuser  = user1.copy(id=25)  //copy the id to new instance

prinln(newuser)

}

data class user(var name:String,var id:String)  //this is data class

Object Declaration :-

Acted as class having static method and Variables

use keyword 'Object'

Cannot have constructor

can have superclass & init

fun main(args:Array<String>){

    customerdata.count = 98

    println(customerdata.count)

    customerdata.count =22

    println(customerdata.count)

    println(customerdata.type())

  customerdata.mymethod("Hello")}

open class supera{

    open fun mymethod() {

        println("mysuperclass") }}

object customerdata : supera(){   //object declaration

var count:Int = -1   //behaves like static method

 fun type():String {

        return "Indian"}

  fun mymethod(input:String) {   //behaving like static method

 super.mymethod()

        println(input)}}

Companion Object :- 

Same as object , but declared within class

fun main(args : Array<String>){

    my_class.count =78

    println(my_class.count)

    println(my_class.customer_type())}

class my_class{

    companion object{

        var count : Int = -1

 fun customer_type():String {

           return "Indian" } }}