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[MUSIC]

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[SOUND] Welcome back!

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I have solicited some feedback and
some example stories for

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us to ensure that our program is
working the way that we wanted to.

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We will use this information to
iterate and improve our program.

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I'm excited [LAUGH] to look through these.

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Let's look.
Here's the first one here.

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It says, Craig is a big dork.

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Nice.

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While true, it's not very nice.

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Okay, let's look at this other one here.

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[LAUGH] Of course it starts the same way.

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Craig is a, what does that even mean?

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[LAUGH] Well, one thing is certain here.

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We are going to need to put some
sort of age restriction on this.

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After just reviewing those first
two responses, I am certain

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that we better limit this from getting in
the hands of someone under the age of 13.

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So, let's write some code that
stops the program from running,

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if the user doesn't meet
our age requirements.

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In order to do this we're gonna
need to pick up a few new skills.

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To put this age restriction in place,
we are going to need to work with numbers.

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Now, Java has a data type that deals with
whole numbers, and it's called integer.

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We'll store the user's age in
a variable of the integer data type.

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Then we're going to use what is
known as a conditional statement.

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Conditionals help us to make choices
based on information we know.

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We make decisions like these all the time.

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A clear example is to take a look at
the conditions that are made by users of

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an online dating program.

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I will go out with that guy, if he
doesn't smoke, doesn't have kids, and

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likes to go to concerts.

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Or, I will date anyone who is
older than 28 and less than 50.

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Only after these conditions
are met is contact made.

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So the conditional we are specifically
looking for is, is the user older than 13?

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The answer that we get back is
either yes or no, true or false.

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In Java this is a data type
referred to as a boolean.

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And last but not least, we'll learn
how to immediately exit the program so

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that it doesn't continue running
after we've decided they aren't

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old enough to use the program.

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Are you ready?

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Let's go put a PG13
warning on this program.

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All right, so first things first,
we gonna make a new variable called age.

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So remember,
we're gonna make an integer data type.

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So the way we do it is we start by
stating the data type name, which is int.

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And then we type the name of the variable,
which is age.

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And let's go ahead and
set ourselves up to fail.

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And let's set it = 12.

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And then we'll press the semi-colon of
course to end the statement, great.

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Okay, so now let's go ahead and
add our conditional.

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Now remember, we're gonna check and
see if the person is younger than 13.

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In other words,
if the age is less than 13, exit.

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Okay, let's write that.

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So, first we'll write the keyword if.

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And then we'll add an open parentheses.

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And here's where we write our expression.

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And that's the condition that must be
true for the code following it to run.

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So, which we said earlier that is age.

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And then we're gonna do < 13.

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And we're gonna close the parentheses,
and we're gonna give a space and

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a curly brace.

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And a curly brace opens
up a block of code.

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And so let's just go ahead really
quick and add a comment here.

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And this is where we're
gonna insert our exit code.

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And then let's close that curly brace.

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You could have many lines of
code in this code block here.

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So let's go ahead and

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let's add a new line that says that
they're not allowed to use this.

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So, we'll say, Sorry you must be
at least 13 to use this program.

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We're gonna go ahead and
do a new line sequence in the quotes, and

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the semi-colon.

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Okay, now what we'll do is we'll tell the
program that it's time to quit or exit.

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So far the only object that we've
really used is called console, but

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we're about to see a new one.

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And that's the global system object.

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This object has a method
on it which is called exit.

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Which as you might guessed,
causes the program to exit.

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The exit method takes an argument for
the status code,

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which zero means that the system exited
intentionally, we had control of it.

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Any other non-zero value represents a
status code that is used to state that it

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exited abnormally.

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So let's go ahead and write that out.

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So again,
that's System with a big S dot exit,

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and then the status code of 0, great.

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I'm gonna save that.

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And let's give that a go and
see if it works.

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Let's run that, and boom.

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Now because we hard coded, again,
we hard coded the edge up here at 12.

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It is always gonna run into this if block.

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And these two statements are gonna run.

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And it's gonna exit and
the rest of the code won't go.

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So we won't get prompted for
the rest of these.

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So it's working, great!

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Wow, lots of good stuff!

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We use a new data type, we learned
about if statements and code blocks.

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And learned how to safely
exit from our program.

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One thing that I wanted to point out
about the int data type was that it was

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all lowercase,
unlike the other data type we had seen.

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Remember that was the string
with a capital S.

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When a data type is lowercase it is
a special kind of data type called

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a primitive.

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int is one of eight primitive data types
that come out of the box with Java.

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Basically, primitives have
special characteristics

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about the kind of data they can store.

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And that's about it.

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They don't give you methods or properties.

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They're just data.

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How primitive, right?

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For now, I just want you to be
aware of the term primitive

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in case you run into it.

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So, int is a primitive data type,
and string and

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all other non-primitive types
are called object data types.

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Check the teachers notes for
more information.

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[SOUND] Now our application is
safely blocked from pre-teens.

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Well, actually, at the moment it's
pretty much blocked permanently, right?

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We need to make that age variable
dynamic by prompting our user.

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But before we get there,

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let's do a quick exercise to make sure
all this new information is making sense.