Java Programming Tutorial - 61 - Simple Polymorphic Program Video Lecture

what's going on guys welcome to your
sixty first job tutorial and this
tutorial is probably going to be the
last tutorial for now on polymorphism oh
so I flew so in the last couple
tutorials I told you guys about the
concepts of polymorphism and I showed
you guys how to do some pretty cool
stuff of them but we never really put it
into a program and we never really got
to see why this was really useful so in
this program I'm going to show you
pretty much the core heart of
polymorphism and what you can use it for
so let's go ahead and in this program
I'm going to make a method in each one
in these classes that's just going to
say I don't know I'm going to have like
a line for fish that says make a noise
I'm going to have a line for dog that
says make a noise and by line I mean
method and also one for animal as well
so let's go ahead and make the same
method and animal fish and not dog and I
probably should have made an animal that
makes a noise besides fish but you know
fish don't really make noise but that's
not important you'll see what this
tutorial is about so let's go ahead and
make a method in here for an mo and
we'll put public void noise and since
animals don't really make a noise let's
just have something on the screen
because this method is actually never
going to be called but I just want to
make a method to show you guys it's not
going to be called so system.out.print
line
gotta learn to type print line and we'll
say like animals don't make noise and
this is pretty much a point of
inheritance and why we have this um
class right here because fish and dog
are each since they extend this they can
both override this method right here so
let's go ahead and copy this in the fish
one let's go ahead and put the same
method in here again we don't change
your name of it it's just the noise one
but it's coming from the fish class now
and what kind of noise does a fish make
put like blurp slurp that's what noise
I'll make if I was a fish so you know
it's good enough dog one should be a
little easier
we'll put a method in dog called
boys as well and will make this one go
grow not rust rough right like that so
now we have this method called noise and
animal and we also have a method called
noise and fish even though fish don't
really make noise but this fish says
glib slurp and we have one in dog called
noise called a ruff
so we have this main method and animal
and it gets overwritten when you call it
in dog and fish so now um that we have
three methods
named the same thing let me show you
guys the core heart of polymorphism one
of the main aspects of polymorphism is
that it you can put objects in wood an
array like we did last time but we
didn't really do anything with it we
just added them into the array the cool
thing is that you can put objects in an
array and you can loop through that
array and call the same method for the
objects the thing is you can
automatically call a noise for dog and
when you call noise for dog ruff prints
out and when you call noise for fish
glare slurp comes out and if we had a
burden you call noise for bird it'll be
chirp chirp if we had a class called cow
and the math Conroy's oh do Moo so it's
pretty cool in the sense that you can
loop through an array of objects and
call the same method arm the same method
name but each method since it's in a
different class it does something a
little different and this is my virus
protection right here so I will renew
that later get on my way get get so let
me go ahead and show you guys how to do
this go ahead and make an animal type
object which is actually going to be an
array so go ahead and write animal and
one name in the list and we'll set equal
to new animal too and again the concept
if we have an array of type animal then
not only can we put animal objects in it
but also fish and dogs and say extend
animal and that's one of the concepts I
tell you guys before now we can actually
put it to use into something useful so
now we go ahead I mean we need this
is going to be a rate of objects of two
objects so actually this is three but
let's go ahead and make a dog object and
the fish object to use it I can go ahead
and change it
well it's good so dog D equals new dog
with empty parameter since then I have a
constructor or nothing so fish F equals
new fish no parameters for that either
so now we have an empty array in two
objects D for dog and F for fish
so let's go ahead and use those right
now we'll just uh do this the easy way
the visual way so at index zero which is
the first element let's just go ahead
and set that equal to D for dog and at
the list and then index 1 which is the
second element set the equal to F for
fish now let me get this out way this is
annoying
so now we have an array and we have two
elements in it and again if you watch
the last tutorial you can see that you
can populate this array using add method
but this is just a really easy method
method for demonstration the next thing
I'm going to do is write one of these
enhance for loops and in case you forgot
want to enhance for loop was it pretty
much is a special loop to loop through
an array so first you put animal and
then you give a new variable what's
going to use X it's kind of like the
counting variable in for loop and then
you write the array name so now it's
going to loop through the array the list
and every time it loops it's going to
treat the index as X so we can do things
like this X which is the object now
since we put objects in the array so
this would be substituted for D the
first loop and F the second loop and
then you should be X dot noise and what
this is going to do in essence it's
going to loop through the entire array
and it automatically knows the length of
it so you don't got to worry about
counting variables or anything the first
thing it's going to do is say alright
what's the first element in the right
it's a dog so I'm going to put dog dot
noise and I should have ruff print allen
screen alright done with that now next
element in the array it's a fish element
so I'm going to but fish noise and the
fish noise is glib slurp and then I'm
done and that's it so let me go ahead
and run this to all those then you see
ruff glare slurp so that like I said is
pretty much the core essence of
polymorphism in the sense that you can
automatically create an array of objects
and loop through that array and call
each method with the same name in that
object and you don't have to create a
bunch of objects you don't have to be
like D dog F fish this is a real quick
way if you have like 100 or excuse me
and 100 what I keep saying in hundred a
hundred objects so you don't have to
call a hundred lines of code you can
just make this and it loops through so
in the next couple of tutorials I don't
feel like doing any more polymorphism
because kind of annoying ant but I
needed to teach you guys with like
implements and abstract classes were so
that's why I did this because in the
next tutorials we're going to be getting
the gooeys more and some awesome visual
stuff so thank you guys for watching
this tutorial don't forget to subscribe
the next tutorials are going to be
awesome so again thank you guys and I'll
see you next time