#8.5 Kotlin Tutorials for Beginner: Overriding Properties and Methods during Inheritance Video Lecture | Kotlin Tutorial for Beginners: Learn Kotlin in easy language - Back-End Programming

let us now proceed and check out how do
we implement the concept of overriding
in case of Kotlin so for those who do
not know what do you mean by the concept
of overriding in case of Cortlandt
please do not worry we will check out in
this demo video with the help of example
now suppose inside open class animals if
I write suppose animals eating and now
here inside the main method let us do
one thing let us remove all these code
and let us simply call dog dot eat and
now also let us call wear cat equal to
new cat object and then simply call cat
dot eat and now let us run the code and
let see the output so here inside the
output console we get animal eating and
animal eating both the times now if you
notice here I was calling dog dot eat
and cat dot heed now what if I want to
print dog is eating and cat is eating
for both dog and cat object respectively
so for this what we need to do is we
have to apply the concept of method
overriding in case of Kotlin now there
are certain rules that we need to follow
in case of Kotlin to apply the concept
of overriding in case of Kotlin so here
in case of dog let us override this eat
method now overriding means is
redefining and modifying this method
inside the derived class or the child
class so here I will simply use fun eat
and then simply define a print statement
let's say print line dog is eating now
here the compiler is not happy now
similar to class each of the method that
we defined has a public and also final
keyword by default attached now this
method
function it also has the final keyword
here that simply makes it impossible for
the child class to override this method
here so for that here we need to define
the keyword of open
now once this method is now open which
means now this method can be overridden
inside the child class that is inside
the dog class again here it shows some
error we need to use the override
keyword override space function eat so
this tells the compiler that we are
simply overriding this method from the
parent class that is defined here inside
the animal class and now same thing
applies inside the class cat as well
here let us copy this code and paste
this here and here I will simply use cat
is eating and now let us run the code so
here we get dog is eating cat is eating
so this is the beauty of using the
concept of method overriding in case of
Cortlandt now notice here this eat
method is exactly same as this eat
method the only difference is that here
we are printing animal eating and here
we are printing dog is eating like this
now suppose I create an animal object
let us say wear animal and then simply
call animal dot eat and now let's see
what happens so here we get annual
eating in the output so what is
happening is that when this statement
dog dot eat is executed the compiler
gives more priority to this eat method
now similarly when we call animal dot
eat with the help of this animal object
the compiler only looks for the eat
method inside the animal class right so
here we get animal eating and this
animal don't have a superclass right so
by default this eat method will be
called now same thing applies for the
cat object as well cat dot eat the
compiler simply looks for the eat method
first inside the cat class so here we
have overridden eat method here cat is
eating is now printed in the output
console and now suppose if I want to
print the animal eating as well as dog
is eating when we call this statement
dot dot eat so in that case what to do
so here let us remove all these lines of
code
and here what I will do is inside the
dog method inside the overridden method
I will simply use a super keyword super
dot dot e so when the statement eat
method is executed it's simply called
super dot eat method that simply
triggers this method present inside the
animal class which is actually the
superclass right so this animal eating
will be printed and after this the
control will enter this statement so dog
is eating will also be printed in the
output console and now let us run the
code so here we get animal eating and
also dog is eating now notice from the
main method I am simply calling dog dot
eat only once right so when this
statement is actually executed it simply
triggers this method over here which in
turn simply calls the eat method inside
the animal class and then after this
this method dog is eating is now printed
along with the animal eating so I hope
the things are now clear now when were
concept I want to tell you now suppose
this dog simply inherits from the animal
class now suppose here if I define comma
or interface name such as such as let's
say test right suppose this test is
actually the interface now what is the
interface I will let you know shortly in
my upcoming tutorials but as of now
suppose I have animal which is the class
comma test which is actually the
interface so this will simply create a
confusion for the compiler if this test
message contains the eat method as well
like we have eat method inside the
animal class in the same way suppose
each method is also present inside the
test class so in that case it will
simply create a confusion for the
compiler so here just to be on the safe
side I will simply use super followed by
left arrow and then right arrow in
between simply give the type as animal
class and now let us run the code so in
the output again we get animal eating
and dog eating
right so this was all about the method
overriding in case of Cortland now what
about the field variables or the
properties overriding in case of
Cortland can we override this color
inside the dog yes we can suppose by
default the color of the animal is let's
say white and now suppose from the main
method if I simply print let's say print
line dog dot let's say color and let us
remove this statement dog dot eat and
now let's see the output so in the
output we get white right which is
actually the default value provided to
the field variable of color inside the
animal class now suppose I want to
override this color property inside the
class dog in the same way we have done
with the eat method so for that again we
need to declare where space color of the
type of string equal to let's give the
default value as black right now here it
will simply show us the error and here I
have to use the keyword of override and
now here again it will show some error
right now this is simply because like
like the class and also the method the
where keywords or the variables are also
public and final in nature so by default
you cannot override this variable inside
the dog method till it is final in
nature so similar to the animal class
and also the function eat we have to
make this variable as open and now this
variable color can now be overridden can
now be overridden inside the dog class
like we have done here right now and now
if I run the code then this statement
will be executed dog dot color so the
compiler will give more priority to this
color variable present inside its own
class definition of dog right so instead
of white this time black will be printed
so here in the output this time we get
black instead of white so always
remember in order to inherit some class
we need to use the keyword of open in
order to override some property and also
some method we need to use the keyword
of open and if you are overriding
something you need to use the keyword of
override here and here as well so this
was all about the method and properties
overriding in case of Cortland it was
very simple and clear