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Sometimes you won't know the top end of a range, this is where infinite streams come into play.
Whoops!
A fellow student, David Lin, points out very wisely that I made a common mistake and the code should actually be subtracting 1 from my index.
Thanks for pointing that out David!
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So now that you've seen ranges in action,
0:00
you might be wondering how you do
the step portion of the for loop, right?
0:03
So this old school for loop here,
that's this i++, right?
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So each iteration, what should happen?
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Now in a standard for loop,
you just increment your index.
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But you can do other things,
maybe you wanna increment it by 2 or
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something like that, right?
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So that's called stepping.
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So this is a little bit of a stretch but
I wanna show you how to do that
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declaratively in case
you run into that need.
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Okay, so let's say,
let's see how many companies we have here.
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How many companies are hiring?
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Over a thousand jobs posted yesterday,
let's see.
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657 companies, okay.
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So, that is too many to display in a menu,
obviously, right?
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Let's say that we wanna
show 20 pages each.
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But you wanna choose from each
one of those pages, right?
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So we wanna show every 20th page, what
would be the first company on that page.
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And then that go kinda let you
choose where in the alphabet to go.
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I know it's a bit of a stretch but
it's something fun to play with.
1:02
So in order to do that,
we probably wanna say that our page size,
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we'll set a new variable, page size is 20.
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And let's calculate how many
pages there actually are, right?
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So we have companies.size and then we'll
divide that by the page size, okay?
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And then that way we can change that and
this will dynamically fix itself.
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Okay, so, there is a method on
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IntStreams that will generate
an infinite stream of values.
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And it's called iterate.
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And what iterate does,
is it takes a seed or a starting point.
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So in this case, we're gonna start at 1,
just like we did before.
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And then each time it's called upon,
it takes the last value, and
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runs it through a function.
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So that function is gonna take an i,
we'll just say, i + pageSize, right?
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So each number that this
generates the next one.
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So the first one will be 1,
the second one would be 21.
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And the next one would be 41, right?
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So it's gonna add 20 each time,
that's what we're gonna do.
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So we'll use very similar logic to
convert our item as we did before.
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So we'll say, .mapToObj, and
again, that's gonna take an i.
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And we'll do String.format.
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And we'll give it a d, %s.
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And very similar, we'll do i and
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we'll do companies.get(i).
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Now the reason why we have the page size
is to make sure that we can limit this.
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Otherwise, it will just keep on running,
we need to tell it when to stop.
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So we're gonna limit it
to the number of pages.
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And obviously,
if it went past the number of pages,
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our companies.get(i) would
be out of balance, right?
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Because this is not gonna stop,
this is not based on any top level.
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We didn't specify the end of the range.
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We specified an infinite stream.
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And then finally, let's print out our
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Cool, so
let's take a look what this looks like.
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Cool, awesome.
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So there, right?
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1, 21, 41, and that's happening
because it's going across here.
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So again, I just wanna show
you that this is infinite.
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And you can actually create infinite
loops in functional programming.
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So check this out.
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I'm gonna do this.
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I'm gonna remove the mapToObj
because we obviously,
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we don't want that to go out of bounds.
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And I'm also gonna remove this limit here.
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I'm just gonna go ahead and
just show you what happens.
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And there, it's very quickly.
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My machine's whistling, I'd better
turn it off, I'm gonna click stop.
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That was close.
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So, there are going to be many times where
you don't know the high end of your range.
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And using infinite
streams is the way to go.
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>> All right, now that you've
gotten smitten with streams and
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all their amazing aggregate functions,
I think we're ready to start
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unparking those items that we've
added to our parking lot document.
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And start diving into the fundamentals.
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Now that you've seen how these
things work in Java specifically,
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let's take a look at the fundamental
concepts in broader strokes.
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This knowledge will prove critical as
you design your functional solutions.
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Let's take a quick break.
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And I'd like to make sure you come
back to the next stage refreshed.
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You're doing great.
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Go get some fresh air,
get your blood pumping, and
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get that brain ready to learn.
4:26
Let's do this.
4:28
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