Java Programming Tutorial - 59 - Class to Hold Objects Video Lecture | Java Programming Fundamentals: For Beginners - Back-End Programming

what is going on guys welcome to your
59th Jeff tutorial and if you've been
watching last couple tutorials then we
pretty much learned all the really basic
concepts of polymorphism and inheritance
and stuff like that so in this tutorial
we're going to be putting all our
knowledge to use and building a program
that pretty much gets a class in puts
objects in an array and it sounds
confusing but um you're going to see
what it is eventually but before I get
into program and I want to show you guys
that I got rid of all my other classes
because I'm going to need a better
example and I thought that this would
clearly or better demonstrate so I made
a new dog class and I made a new class
called fish in that I made a new class
called an animal and since dog is an
animal and fish is an animal then I had
them both extends or inherit from the
class animal and I didn't want to do
that just because it took time but I
pretty much made these classes and I
have nothing inside them so if you want
to go ahead and do that you can follow
along with me so then here's a scenario
we made these three classes called dog
fish and animal and our boss comes in in
he's like alright Bucky I need you to
program something for me I'm like what
is he's like I need you to make a new
class called mmm well name it dog list
or something like that and in this class
I want you to have an array that we can
add dog objects so like I said an array
can hold many things again hold numbers
again hold strings it can also hold
objects and this comes into use um well
we're going to be finding out why a
little later but in this tutorial we're
going to be building a new class in a
new array to hold dog objects why
because our boss told us to so let's go
ahead and do it the first thing I want
you to do is go ahead and under package
under your source right click it and
click a new class I know you probably
can see it so I will move it down source
new Wow now you really can't see it but
anyways if you click a new and class you
get this thing that pops up and just go
ahead and put dog list or something like
that and now let me move this back so
there we go
now we have let's see one two three four
five classes and we have this new dog
list class and in this class we're going
to be building an array to hold objects
from this dog class and the fact that
extends animal is irrelevant for now so
we have this dog list class and our boss
wants us to build an array so let's go
ahead and do that first let's go ahead
and make a private because no need to
make public dog and we're putting dog
and we'll name the array the list and
we'll set this equal to new dog with
parameter of five or an array length of
five and we put this dog and dog even
though we named the array the list we
put dog and dog right here because that
is what objects it's going to be holding
it's going to be holding stuff from the
dog class so now that we have an array
named main list let's go ahead and the
only other thing we're going to need to
work with our Ray is a counting variable
so let's go ahead and name private eye
equal zero
you can set equal to X if you feel more
comfortable with that boat what's this
error saying right here all right we
need an int private int I equals zero so
now we have an integer that's just a
counting variable that's going to help
us work with our array so now let's go
ahead and build a new method to add dog
objects so again or not again we need a
method named public void we'll name it
add you can name here's what everyone
I'm just going to Emma add because it
makes sense and as a parameter whenever
recall this it's going to take a dog
object and we'll name it D for now short
and sweet and the first thing we want to
do in this method is do a if statement
so let's go ahead and make if and we'll
put I which is our counting variable
that 0 now is less than the
list dot length and what this pretty
much does is check if your array is
fuller or not so if I the counting
variable is greater than five then your
arrays already full so it would just I
mean the method to run but it wouldn't
add another one to array because this
can only take five elements so four
seven and we try to add one then it
wouldn't do anything so if it is less
than length which means if it still has
room in our array what do you want to do
well the first thing that we want to do
is put the list and I which would be 0
now we want to set it equal to D so
we're pretty much just going to loop
through the array and every time we call
this method add an object to that array
element then just give us a little um
system.out.print line on screen
something that says like dog added at
index space and we'll pie right there
come on come on there we go and we'll
just let's go to right now so now we
have just a little something on our
screen that we can see visually because
you know we want some feedback here so
next we'll just increment through I so
here's what this method is doing it
pretty much checks if your rate is full
or not if not it adds that object at
that index and then it says just gives
us the little message on the screen and
then it goes to the next counter so we
don't keep adding it in the same index
in our array so now we built this class
just like our boss said that has an
array name the list and it's going to
loop through every time you call this
method it's going to add a new object to
the array so let's go ahead and do this
in our own main method I named mine
apples I don't know why but I did
so now let's go ahead and make a dog
list object so let's go ahead and put
dog list I'm going to need my diello you
can name your object anything you want
and then just put equals new dog list so
you should look the exact same as mine
except if you didn't want to name it
diello you don't got a
so now we can go ahead and create a dog
object because I mean we need one as our
parameter so we create dog D or if you
don't have a dog class then whatever you
have and we'll set it equal to new dog
object just like that doesn't take any
parameters because it doesn't even have
any constructors or anything now what we
have to do is pretty much call the
method in our dog list so use that
object
diello whoa embarrassing diello that's
our method type it and we have a method
called add in there remember that's what
our method was called and it takes a
parameter of an object a dog object and
we have a dog object right here dog D so
let's go ahead and put D as our
parameter right there and that's it
pretty much just to run this baby click
OK and now if everything goes right it's
just say dog added at index zero and if
we added another one I would say dog
added it index 1 and we'll go 2 3 4 and
it will go all the way and that is
because we set this equal to a length of
5 which means index 0 1 2 3 and 4 so
that's your real basic tutorial on our
how to create an array to add objects
into it but then what if our boss comes
in and says yeah come in boss hey Bucky
I got a little problem what's that boss
alright you know how I told you create a
dog list to hold dog elements or excuse
me dog objects well now on the people
were working for they said all right I
want it to hold fish elements too so how
are we going to fix this problem well
that is a problem for the next tutorial
and that's what we're going to be doing
and trust me you don't just add another
entire class called fish what we're
going to do is making this bigger and
better and you know it's just going to
be awesome and you're going to learn a
lot in next tutorial so thank you guys
for watching
and another thing um my 500th video that
I add I have like 491 my 500th video is
going
be the best video in the biggest
surprise for you guys ever so you do not
want to miss this 500 video it's
probably being released this weekend but
is going to be incredibly awesome and
trust me you guys are definitely going
to want to see it so for now thank you
guys for watching don't forget to
subscribe and I'll see you next door