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Okay quick, so I don't forget, watches.

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So you can create expressions that
constantly stay bookmarked, so

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let's do that over here.

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Okay, so I'm gonna click our cardCounts
variable that we determined up here,

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it was so important.

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And I'm gonna right click it,
I'm going to choose Add to Watches and

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it adds a little glasses like
on here with cardCounts.

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There's a way that you can
make a separate panel.

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I like this version a little bit better.

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They made it so
that you can have more space but

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I'm gonna click this and
now you'll see that there are separate,

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you got Variables and
Watches as two separate things.

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One of my favorite things about these
watches is that they stick across frames.

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So for instance, we're basically
done with our current frame right?

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We're gonna return this value and the
frame is gonna be popped from the stack.

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Are we ready?

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Boom, and now we're back where we started.

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Now notice our current execution point,

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we haven't set the cardCounts variable yet
and that's why this right here can't find

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the local variable cardCounts
because it doesn't exist yet,

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so I'm gonna go ahead and step over and
now that it exists, look it's stuck there.

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So we can see know that there
is the cardCounts value here and

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it's the cardCounts values here as
well but it's also showing over in our

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Watches because we're remembering
that that's what we wanna watch.

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There could be tons of variables there but
one thing I wanna point out is that

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the reason why this is working is
because the name is the same, okay?

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So we're watching an
expression called cardCounts.

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Okay, so let's step in to our next method
here which is getNextFlashCardBasedOnViews

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and we're gonna pass in
the object reference cardCounts.

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Okay, so here we go.

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So we'll step in and here, uh-oh,

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it says cardCounts can't find
the local variable cardCounts.

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And that's because it's been changed.

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It's called idToViewCounts,
it's more specific, okay?

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So, well,
that actually helps a little bit, right?

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So that's helping me
understand what this is.

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So its id must be the key and

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the value must be how many
times a card's been viewed.

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That's my current assumption at least.

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So what now though?

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Our watch isn't picking up this
value in the current frame.

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Now I could, of course,
add another watch super easily, right?

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Like I could just right click that,
choose Add to Watches, it's there, and

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then if I switch between the frames here,
when I'm looking at this,

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this one can't find the variable and
when I look at the other one,

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it can't find the cardCounts,
fixes the problem more or less, right?

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That's probably enough for most
situations, but there's a pretty nice work

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around that we can use if you don't
mind going on a slight detour with me.

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Okay, so there's a trick, right?

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It's possible that you can label or
mark objects.

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So the usage of labeling is for
various reasons.

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Maybe we don't like the way
a variable's named or

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we want to add specific metadata
about that object specifically.

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Or in our case, we want to see when
it's pointing to the same object.

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So when you mark an object,

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you're marking the object,
not the name, not the expression of it.

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Okay, so we can do that.

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So let's, you right-click and
choose Mark Object and you choose a Label.

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Now, we know what we're talking about,
right?

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We know it's cardCounts and
we know that it's this idToViewCounts.

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So let's call it counts because
that's what we wanna see.

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So now, see when I go back and

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forth between the frames,
the counts sticks, right?

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So the counts is labelled there.

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It's also labelled in our watch over here.

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See that?

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So the awesome trick is
that you can actually watch

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a label not the variable name.

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You can make it be an expression, right?

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So let's go ahead,
let's remove our watches, you can do that,

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you can press backspace or

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down here, underneath this,
you can press the minus key.

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All right, so
we're gonna add a new watch and

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watches can basically be any expression.

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So, I'm gonna say counts and

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then IntelliJ was nice
enough to expose them.

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So, I can say DebugLabel, right?

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And if I press Enter,
now it's watching counts.

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So anything that counts it, so I'm both,

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there's one watch across multiple
variables and it's using this count.

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Cool, right?

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The fact that you can add any sort of
expression there is super powerful,

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you can put whatever in there and

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it will keep evaluating kind
of like a spreadsheet cell.

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So back to our originally
scheduled program.

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So we're just about ready
to call this method, right,

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this method is getNextUnseenFlashCard and
we're gonna pass in our

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idToViewCounts.keyset which at the moment
remember that was empty, right?

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We're looking down here.

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This counts object is empty.

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So there are no keys, so
it's going to return an empty set.

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So what's gonna happen, terminology wise,
when I step into this method call?

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Can you recall the terms?

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What's gonna happen?

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That's right, it's going to push
a new frame onto the stack for

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this specific method call.

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Okay, so yeah look at this.

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The parameter name is seenIds and we've
passed in the keys of that ID to count.

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So I'm fairly certain that my assumption
was correct, our counts label here is

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a map of IDs to the number of times
that things were viewed, cool.

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So let's walk this logic.

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Okay, so there's no IDs at all yet
as we haven't seen anything,

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it just returns a list of all of them,

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right, so yup, there's no seen so
it's gonna turn all of them.

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So unseen here should be every card,
right?

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Remember there's 8 cards.

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Okay, and since there is no unseen,
we're gonna go ahead and

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come in here and
it's gonna pull out a random card.

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So I can just go ahead and
like we saw before,

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I can highlight this and we'll see that
it's gonna pull out a number, right?

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It's gonna pull out an index between
zero and whatever the number is.

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So if I do this, if I highlight all this,
this should give us a random card.

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Yeah, so there so
I ran that expression and

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pulled out a random card, pulled randomly
the first time of all that you're gonna

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need because it created a new random and
it was somewhere in between zero and

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the top of the array, so that's how
you pull something random, cool.

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So I'm gonna step over to that, and

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the card that we got pulled out
is Java EE Enterprise Edition.

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Okay, so that card got pulled out.

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So now our frame is gonna
pop off the stack and

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it's gonna return to
the getNextFlashCardBasedOnViews.

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Since we have one,
I'm sorry getNextUnseenFlashCards, so

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there was one that was unseen, so
we're gonna make sure that we show that.

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So that returns a card and that pops
off and we're in the last one here,

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and so we do have a card and
we're gonna return redirect link.

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And if you accidentally click
step over like I did right there,

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you'll be dropped into
the magic of what's going on.

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It will give you some great
experience in how amazing

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this open source stuff is that we're using
because of all this code that's right

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there no matter what we're thinking about
but if you don't want to sit there and

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spend the time walking through it,
you just press this Continue button.

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Now if we look back over,
we'll see our Java EE.

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So let's just finish the flow once through
just to feel a sense of accomplishment.

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Okay, so let's see what happens.

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So it generated flash card
ID which is mapped here so

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let's drop this,
we're gonna go ahead and call next.

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And here we are we're stopped and now
we'll see that our counts has a size of 1

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and 5, I'm assuming must
be the ID of the Java EE,

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right, so
it's calling getCardCounts, right,

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cuz we have a breakpoint in
our getCardCounts up here.

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So it's calling that and
it's gonna get it out of the session.

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Cool, so
Java EE has been seen once, right?

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And so we're gonna return the card counts.

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Step over that.

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Okay, so what is this doing?

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This is Java 8 new map compute function,
okay?

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So what that does is it takes a key and
a remapping function.

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So let's suppose that we wanted to break
into this lambda right here to see

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actually what is this doing so
I'm going to click right here.

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And you'll see that I get
a choice between the lambda and

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the line itself, so
I'm gonna use the lambda and

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I'm gonna click the run and
now we're actually in here, okay?

153
00:08:07,489 --> 00:08:12,481
So we're here, so the key, I got passed
in is 4 which must be the new card that

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we're looking at, must have the id 4 and
it hasn't been seen yet before.

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00:08:18,070 --> 00:08:22,110
Okay, so what it's gonna do is, it's
gonna say, if it is null, which it is,

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it's gonna be 1.

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Otherwise, it's gonna increment, cool.

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So it will increment if it exists,
and then if we continue out of this,

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we'll see that the card gets
pushed in the template so

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the second was Java SE and
it was seen one time.

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00:08:39,488 --> 00:08:44,382
Awesome, and let's click Next one more
time and we'll see that our cardCount

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has now has 4 which is that idea we saw
and 5 and they both have view at one time.

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Cool, all right.

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So now that we've got the basic idea for
the flow, let's take a quick break.

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I'm gonna go jog around my yard real
quick and get my brain working.

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I find it's good to take breaks and
let all that we just learned about the way

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00:09:01,140 --> 00:09:04,090
that our app is working kind of
work its way into our brains.

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00:09:04,090 --> 00:09:07,100
Then when we're refreshed,
let's go grab another one of those issues.