Java Programming Tutorial - 23 - Compound Interest Program Video Lecture

sup guys welcome to your twenty-third
tutorial and this tutorial we're going
to be building a simple program so now
that we learn what the for-loop was I'm
going to be building a program to
calculate something called compound
interest and this is pretty much like
interest if you put your money in like a
savings account or something you it will
allow you to see how much money you have
in future well I'm going to be using it
for is to see how many subscribers that
I'm going to have in the future so right
now if you're watching this tutorial and
I'm making this one I have about 10,000
subscribers and I figured out that I
gained one percent of my subscribers
each day so with that information I'm
going to be able to calculate how much
subscribers or how many I'm going to
have in future so the formula for
compound interest is this a which stands
for the amount and this is going to be
what we're solving for the future amount
equals P which is the principal which is
10,000 times 1 plus R and again R equals
the rates and all of this is ^ where the
power of N and n is the number of years
so we want to solve for a and what we
need to do is find P which is the
principal 10,000 times 1 plus 1% to the
power of n and this the number of years
so if this sounds really complicated let
me show you guys how this using a for
loop and you will be substantially
impressed I promise you so we need 3
variables a double amount and we don't
know what this is yet so we're just
going to leave it set to nothing double
principal in again we're using double
because we want to use what's it called
decimal points we can't use int because
these aren't whole numbers we need to
use decimal points
a double principle we know this is
10,000 since that's how many subscribers
I have to begin with and don't put the
common there 10,000 so we have the
amount the principle and I told you guys
the last thing they need is the rate so
double rate equals point zero one since
I'm gaining subscribers at one percent a
day so now that we have the amount that
which we're solving for we have the
principal the value that I'm starting
with and the rate 1% a day we can go
ahead and make a for loop to build this
program so go ahead and all this for
loop is going to do is say how long do
you want to run it for well let's go
ahead int and day we want to start with
the first day and we want to go to day
20 we can go to whatever we want just
but less than or equal to 20 and put day
plus plus and all this says is start on
day 1 give me all the information from
day 1 to day 20 that's all this does now
let's get the good stuff we want to
solve for amount so that's what we're
going to be setting equal to since we
don't know what it is yet but we do know
what the formula is for it it's
principal and make sure you type these
right principal and again you need the
time to spy something to the power in
this calls for an outside method that's
math pow now again you can see right
here that it takes two arguments the
first argument what's in the parentheses
and the second arguments the exponent so
again let's go ahead and add those
arguments right here the first thing
what's in the parentheses is 1 plus rate
and what do you want to give the
exponent year or let's see what it was
day actually so now we have 1 plus rate
which is a amount equals principal which
is 10,000 times 1 plus 0.01 to the day
and that day is going to loop so now all
we have to do is print this out on the
screen
system.out.print line and let's go ahead
and print a year actually day again
whenever you use like a compound
interest and stuff you usually use a
year but uh no one really uses day
unless you're you're looking at YouTube
subscribers so that's what I keep typing
year plus and add a couple spaces amount
there you go
so let's go ahead and run this and I'll
show you guys what it does so now we
have a list down here that says how many
subscribers I'm going to have each day
so on the end of the first day or after
one day I'm going to have um 10,000 100
subscribers that sounds about right
that's 1% and as you can see at the end
of 10 days from now I'm going to have
1146 subscribers and a couple half-half
subscribers here and at the end of 20
days I'm going to have over 12,000
subscribers so that is how you can build
a program to calculate something like
investments or your mortgage payments or
something like that again let me show
you guys how this works one last time as
I always do we needed three principal I
mean excuse me
principles we needed three variables
because that's how many variables are in
this formula you need to figure out the
amount which we don't know yet but we do
know the principal which is the starting
point and the rate we want to set that
amount what you don't know yet it equals
the principal times 1 plus the rate
which is 0.01 times the day and this
sort of the for loop comes in handy
because this goes 1 2 3 4 all the way to
20 and next we just output it on the
screen so again um if you're watching
this tutorial within Google on what the
formula for compound interest is in
you'll be able to follow along easier
it's kind of hard seeing in this unless
you're looking at the formula but that's
pretty much how you calculate compound
interest so um thank you guys for
watching my tutorial play around
this and I promise after you do one time
you'll be expert at it so again thank
you guys for watching I hope enjoyed
building a simple application I don't
forget to subscribe to my channel and
I'll see you next tutorial