Java Programming Tutorial - 7 - Building a Basic Calculator Video Lecture

what's up guys welcome to your seventh
java tutorial and in this story I'll be
showing you guys how to make a basic
calculator using variables and other
things that we already learned so far so
in your last order I showed you guys how
to get input from a user using something
called a scanner and we're going to need
that again and I already imported it so
the first thing that we're going to want
to do is go ahead and make a scanner
variable so let's go ahead and write
scanner and I'm going to name mine Bucky
again and again I'm going to set it
equal to new scanner and also I want to
put system in so it knows where to get
input from so or a system dot n and
that's all you need to do for now the
next thing we're going to need is three
variables we need one variable to hold
the first number one variable to hold
the second number and our less variable
is going to hold the answer so you can
they're going to be doubles by the way
so you can go ahead and declare them by
writing double F num for first num go to
the next line alright double s known for
second num or here's the neat little
trick if you have many variables of the
same type and by type I mean double or
int or something like that since you
have many double variables you can write
them all on the same line it's a nice
little shortcut so write s num and
answer you can name your variable as
anything you want I just usually have
shorter variables since I don't feel
like type and Hall up so the first thing
we want to do on a character on our
excuse me calculator is just print a
line of text that says enter first
number so the user knows what to do so
go ahead and you know how to write this
system dot out dot print line print line
and your parameters just go ahead and
write enter first num and then put a
little a semicolon right there if you
want and now we can go once we have that
all this is going to do is put a line of
text enter first num on the screen
now what we want to do is have a way to
enter a number and have it stored and F
num so go ahead and press F num equals
Bucky remember this is our scanner
variable and right next double and that
brings me to another point now in our
last tutorial I showed you guys
something called next line and it was
right here and that was for Strings each
data type in Java you need to give it
its own method since you need to tell
what you're going to be inputting in
there so it knows how to save it for
example if this was strings you're going
to input in there like Hello you're
going to put next line but since we're
inputting a number you're going to want
next double because double is the type
of number so now once we enter this
number and it can have decimal points
it's going to be stored in the variable
F numb and we're going to need that
later so now we have to do this exact
same thing for the second number so
let's go ahead and copy this line since
I'm too lazy to type it where's the copy
they are at us and next we want to print
enter second number and now we just need
to do the same thing go ahead and copy
this and after that prompt pops up
you're gonna there we go you're going to
want to store this variable in s num so
the first number you're going to type is
in be stored in the variable F num and
the second number you type is going to
be stored in the variable s num this
stands for first number and second
number now what we want to do to get
that answer that we have those variables
is just add them together so go ahead
and write answer equals and you're going
to want to write F num plus s num and
now we have whatever number that F num
and s num is going to be stored and
answer now it's stored in there but we
need a way to output it to the screen to
see what it was so let's go ahead and
write system dot out the print line and
in your parameters just write answer
this is going to do is output answer
whatever it was to the screen so go
ahead and run this program and hopefully
I didn't get any errors and here's our
program right here enter first number
let's do 30 4.6 move my cursor out of
the way press enter enter second number
um fifty four point two press Enter
it's going to give us our answer eighty
eight point eight zero zero zero one and
this is actually something that I want
to talk to you guys about and I'll be
talking to you guys about it in the next
tutorial well probably not in the next
one but um this brings me to a good
point which we don't have time to talk
about in this tutorial but I will get to
shortly so basically what I did and our
first number entered it and our second
number enter it and then gave us an
answer pretty much and again to walk you
through this one last time
what I did is import the scanner so I
could use the java scanner and then i
wrote everything in my main function
because that's where the computer looks
first the first thing i did was write a
variable for a scanner just so we could
use it next i made three variables that
were double which means numbers first
number second number answer the first
thing i did was have a little prompt
that should set a enter first number
just so I knew what was going on for the
user next I use that little scanner
variable and nextdouble method to have
whatever I typed in the keyboard to be
stored in the first number then I just
had something says enter second number
and then I had it have the user input
something else and wherever they input
at that time is stored and s num and
then I just outputted um whatever those
two were added together the sum of that
and I just printed it out online screen
so that's a very basic calculator and it
had one flaw in it and that was giving
us many decimal points and I'll show you
why that is in
I don't know what tutorial but it's
going to be coming up pretty soon
whenever I deal with numbers but again
that's a basic calculator that's how you
build it using a new method called
nextdouble that we learn and also how to
combine everything we learned so far and
build a function a functioning program
so again practice this get good with it
make sure you understand everything we
did up to this point and once you do
you're ready to move on to my next
tutorial so thank you guys for watching
hopefully I see you next time and don't
forget to subscribe to my channel so
thank you and I'll see you then