Java Programming Tutorial - 30 - Array Elements as Counters Video Lecture

what's up everyone is Bucky welcome to
your xxx Java tutorial and in this
tutorial I'm going to show you guys how
to build a program where you can take
array elements and store them as
counters now we already build a little
random number generator we roll the dice
and we store those numbers but in this
program I'm going to make it a lot
easier and show you guys how to do it
with an array so we're going to be
building a dice rolling it like a
thousand times probably in storing how
often each number pops up so of course
we need a random number generator so
let's go ahead and import java.util
random and now once we imported that we
can use it so let's go ahead and put
random I'm going to call my object Rand
and set it put two new random and we
don't need any ammeter rat and now let's
go ahead and make a frequency array so
just name it freak or whatever
not that kind of freak this kind and
just set equal to new int seven now if
you're saying alright there's only six
sides on the die why am I having seven
elements in my array
well we're creating seven elements
because remember the indexes go from
zero to six zero one two three four five
six since zeros include that seven
elements in we're going to have an array
index of zero and one to six that
American use we aren't going to use six
I mean excuse me we aren't going to use
zero but we need one two six so that's
why we need seven elements so we can get
one two six if we only created six then
it would go from zero to five so now we
can go ahead and make a for loop to roll
the die a thousand times so let's go
ahead and put four and just put in roll
equals one
go start at roll number one and put like
roll if you want to roll a thousand just
go put ahead and put thousand
and of course go ahead and increment
them by one and again this just um loops
this a thousand times so you should know
that but wait I want to teach you guys
is this anytime that rope up so actually
let me go ahead and write the line of
code first and then you can see exactly
what's going on go ahead and take your
frequency array and go ahead you want to
add one two something you want to go
ahead and put your random number
generator in this and ours was named R
and dot next int in of course we want
let's see six now let me show you guys
what this does this is the most
important piece of code in this entire
program and let me break it down from
the inside out this is going to give you
the numbers 0 through 5 as you should
already know what this one does is shift
it all over so you get the numbers 1 to
6 instead of 0 through 5 so if you're
saying all right what's this then
what this does is add 1 each time that
this hits that number so for example um
frequency 1 2 3 4 5 6 are all set to 0
to begin with if this rolls in on the
first roll it gets a 3 then freak 3 is
going to equal 1 if it rolls again in
has a 3 freak 3 is going to equal 2 if
it hits again and again again
3 3 is going to equal 4 or 5 and 6 and
it's going to keep count of all of the
indexes and every time that it hits that
number it's going to add 1 to that index
so let me go ahead and well you'll see
what this does
so the first thing I'm going to add is a
header so you guys actually know what's
going on let's go ahead and print line
and let's just print something like face
the Nats head
frequency I don't know if I spelled it
right but it'll do Pig that will do for
and the last thing we need to build is
just something to output our data so the
only thing we have outputted right now
is a header that says face frequency
next we want to make a table to show you
guys face here is frequency so let's go
ahead and again we need to start at 1 or
remember the first number on the dice is
1 so face equals 1 and face let's just
have it less than freak dot length
remember I showed you guys that and a
couple tutorials ago and just increment
it by 1 and now what do I want to do in
this loop remember this loop is going to
go 1 to 6 and it's basically just going
to make a sees me a table that has the
list 1 to 6 so I want to put
system.out.print line not pront line
can't get it print line there we go
finally and let's go ahead and go face
because that's going to be the first
variable we want output is just the face
this is 1 2 3 4 5 and 6 the next thing
we want output is just a tab to give
some spaces and then after that we want
to output the value of each array index
so put your array name you're right
there and put your indexes right there
so let me run this program make sure I
don't have any errors and I'll show you
guys what we got we got a table that
says face and frequency and again we got
that just by adding this face frequency
and then we have your array index number
and your array value index number value
index number value in again if you're
wondering RA I know right here we
created array with 7 and this equals 6
well actually your array index is
start zero but we just wanted out put on
the table one because we don't need zero
for anything we could have added zero
right there
and when you ran it it'll give us this
it would give us six to one
and it would give us zero but again
since um this dice then it doesn't have
a zero we didn't use it so that's why
zero equals zero so now you can see um
the number one rolled 160 times the
number two rolled 158 times and after
rolling the dice a thousand times here's
the distribution of all that so again
let me talk to you guys one last time
and show you guys exactly what we did
imported random number generator right
here you guys know how to do that we
made an array called frequency and we
set it equal to seven elements in that
array what we did right here was make a
random number generator to roll the
numbers 0 through 5 and we move that
over so it rolled 1 to 6 any time I
rolled one of those numbers it took and
added one to that index or that value in
that array next we just made a header
right here and right here what we did is
we just made a basic table we started it
from zero which we actually started at a
1 by just show the eyes we went all the
way to 6 and this just made a 1 to 6 and
then we just outputted the value so
again we outputted the dice number which
was the index number and the value so
that is how you create a basic um using
elements and storing them as counters
and array so it's kind of confusing but
just play around with it and trust me
you'll get the hang of it so thank you
guys for watching my xxx Java tutorial
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