Kotlin program | Example of inheritance

Kotlin | Inheritance: Here, we are implementing a Kotlin program to demonstrate the example of inheritance.
Submitted by IncludeHelp, on June 03, 2020

Inheritance

Inheritance is a mechanism wherein a new class is derived from an existing class.
All Kotlin Classes have a common Superclass 'Any', it is the Default Superclass with no Super Type declared.
```
class Student  // implicitly inherits from Any
```
'Any' Class has three methods
1. equals()
2. hashCode()
3. toString()
These methods available for all Kotlin class implicitly.
By Default All class is Final in Kotlin, They can't be inherited.

Use 'open' keyword, to make class inheritable,

open class <class name>  // make class inheritable

To declare explicit supertype, placer base class name after colon into the class header.
```
open class Base{}
class Derived : Base{}
```

Program for Inheritance in Kotlin

package com.includehelp

//Declare class, use 'open' keyword 
//to make class inheritable
//Class without declare primary constructor
open class Company{
    //member function
    fun getCompany(){
        println("Base Methods : Company Info")
    }
}
//Declare class using inheritance
class Department : Company() {
    //member function
    fun getDept(){
        println("Derived Method :  Dept Info")
    }
}

//Declare class, use 'open' keyword 
//to make class inheritable
open class Shape(val a:Int){
    fun getBaseValue(){
        println("Base value : $a")
    }
}
//if derived class has primary constructor 
//then base class can initialized there
//using primary constructor parameters
class Circle(val b:Int): Shape(b) {
    fun getChildValue(){
        println("Child value : $b")
    }
}


//Main Function, Entry point of program
fun main(args:Array<String>){

    //create derived class object
    val company = Department()
    //access base class function
    company.getCompany()
    //access derived class function
    company.getDept()


    //create derived class object and passed parameter
    val shape = Circle(20)
    //access base class function
    shape.getBaseValue()
    //access derived class function
    shape.getChildValue()
}

Output:

Base Methods : Company Info
Derived Method :  Dept Info
Base value : 20
Child value : 20

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