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[MUSIC]

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Hello and welcome back.

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I'm Craig and I'm a developer.

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This course is going to build on top of
what we learned together in Java basics.

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If you haven't checked it out yet,

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I recommend that you follow
the link in the teacher's notes.

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It's a prerequisite for

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this course but you don't need to have
any other programming experience.

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And what we're going to learn in this
course is relevant to many other

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programming languages that
you're going to encounter.

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Don't forget that they're speaking
trolls in the video player.

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Feel free to speed me up or
slow me down to your heart's content.

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I won't mind at all.

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In this course,
we are going to be talking about objects.

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Java is an object oriented
programming language and

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literally everything in Java is an object.

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Well, except for
the primitive types like ants and boolean.

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But even those have wrapper
types which are, objects.

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So as you can imagine,
understanding objects

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is super critical to your foundational
base of the Java language.

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And I'm excited to explore them with you.

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So first, we'll familiarize ourselves
with the basics of objects.

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How to use them, how to create them, and

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then after we get a good grasp,
we'll build an application using that.

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The app that we're going to build is
a console based version of the popular

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game, Hangman.

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Along the way will be expanding our
Java toolset again learning new tricks

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as we need them.

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Just like we talked about in Java basics,
there are gonna be a lot of new terms.

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And remember you should feel like you
need to understand everything fully.

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Immerse yourself in the language and
I will cover in detail

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what I believe you need to know at
this point of time in your learning.

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We are going to be using work
spaces again for this course.

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So you can follow along in
code without having to install

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anything at all in your local machine.

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We're also going to be making use
of a tool that might be new to you.

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It's called JShell, and it's the new
REPL that Java just got in Java 9.

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In case you haven't heard of the term
REPL, or R-E-P-L, it stands for

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Read-Eval-Print-Loop, and it allows you
to interact with and explore the language.

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I think you're gonna to love it.

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Let's launch a workspace and check it out.

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Okay, so welcome back to workspaces.

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So down here in the console,
if you just go ahead and type JShell.

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It's going to start up,
it's going to start the REPL up.

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So again that's read a vowel print loop,
check the teacher's notes for

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more on jshell.

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It's super powerful and it's up and

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coming and let's use it right now
it's just refresh ourselves and

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what we've learned so far, it's
an awesome tool you're going to love it.

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So what this will let us do it'll let
us create variables just like we know.

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So we'll do string first
name equals Craig.

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And you'll see what it does there
is it says that it set the variable

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name to Craig.

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It's kind of that's its
style of output there.

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So now we can access
those variables like so.

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So we'll say isCraig and let's see.

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Let's do this firstName.,
to call the method, equals("Craig") right?

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So remember that we we call the equals
method on strings to check equality.

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They're look at stored in the variable now
there's a variable called is Craig and

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you'll notice that I accessed first name.

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So it's kind of in the scope of this this
shell that we're working in here you

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can also just go ahead and
say firstName.equals("Bob).

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And what that did is it
created a new variable.

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Now there's a variable called $3 you can
say it is dollar three equal true and

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it doesn't rank as we know.

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So dollar three is a new variable name and
now I made a dollar four called false.

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So I just automatically
creates these variables and

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it starts with a dollar sign in the front.

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It kinda just stores
whatever is returned right.

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So if I do first name equals ignore
case remember that that was the one that

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allowed us to check no matter if
it was upper case or lower case so

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if I say equals ignore the case.

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Craig it's going to create a new there's
dollar five it's untrue just going to

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stores whatever is there.

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So if you want to refresh your
screen you can do a Ctrl + L.

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And it will bring everything
up to the top there we go.

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So if you did the extra credit on Java
Basics where we tried to validate input

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you learned about the contains into
lower case methods that exist on street,

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let's take a look at them real quick.

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So let's make a new string,
let's say String someWords

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equalas"This is a bunch of WORDS".

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All right.

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So we now have a variable called
somewhere and so if I start typing.

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So in and I press tab it's gonna look and
it will search and

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it will find that I have some words
there so automatically did that and

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it works for methods two so
I did contains a tab and it was over.

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So contains looks for A, the word,
bunch there inside of some words.

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Does it exist?

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It sure does.

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There it is, all right.

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And if I press the up arrow,
things will come back.

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So then, I can use the backspace there and
say does it contain this,

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which it does, right.

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There's this, so there's true.

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And also, if I come and do,
let's see if it has words in there.

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So this is case sensitive.

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So it doesn't contain words even
though it is actually there.

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So we could create a new variable, right.

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We could say string loweredWords
equals some Words and

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remember this is toLowerCase.

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Yep.
And when there's multiple options,

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there so it's gonna show us.

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So toLowerCase is we want, so loweredWords
we could then check if loweredWords,

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Contains words and indeed it does.

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But what if we did the method chaining,

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remember this we could say
someWords.toLowerCase and

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instead of strong that variable,
we can just access it right here.

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It's called method change.

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Remember, we don't even need to create it.

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Cool, all right, so,
we also did some work with integers or

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whole numbers which were like this right.

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So if we say int ageOfBob = 30.

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And let's say that Mary.

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She's 28.

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And we could check and see,

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I'm going to put parentheses around these,
just so

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if Bob is older or
greater than the age of Mary.

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And then again to parenthesis age of
Bob is less than the age of Mary.

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So we talk about numbers
are greater than or less then.

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And finally let's go ahead and
remember that when you get

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a number in maybe you get a number from
a programs coming in you can purse it.

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So let's say that somebody
passed in the string 30,

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you can get the number out with that.

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There you go.

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And finally,
let's remember about Booleans.

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So using conditional logic like and or
ors and those look like this in Java.

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So you say or with a with a double pipe.

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So if we had say false or false,
that's definitely going to be false, but

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what if we put a true here?

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Do you remember what happens?

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So the way that it works is if any of
these are true, it means that it's true.

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And this is the case and or is so
it's like is this true or is this true or

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is this true and it is so there's that and
then if we flip that around again.

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I use the up arrow and

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I'm going to move these to be
ampersands remember how this works.

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This is basically saying,
are all of these true.

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So is false and false and true.

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So it's not, it's not true.

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And actually, what's gonna happen is
it's gonna shortcut the second that it

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finds one that's false.

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It's not even going to need
to look at the rest of them.

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So and again,

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those could of course be expressions like
the age of Bob an age of many thing.

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Feel free to play around here until
you feel refresh what we covered.

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We'll spend quite a bit of time in here
during this course and I'll show you

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a couple more cool things that this
awesome tool can do in upcoming videos.

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Now to get out of here you press Ctrl + D.

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Cool and then you can do clear and
clear the screen.

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Awesome, I feel refreshed.

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That REPL is going to be super
handy going forward, right.

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Now before we get started, I just wanna
remind you that during your learnings here

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if anything at all isn't clear.

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Or even if you're pondering something,
head over to the community and

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share your question with everyone.

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By sharing your question,

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it allows everyone to learn and if someone
else is wondering that very same thing.

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It'll be an answer when
they come to search for it.

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I can't stress this enough, the community
is awesome and supportive and

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I've been blown away by
how quick answers appear.

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I can't even keep up.

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You all are so great.

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All right,
I think we're ready to dive into objects

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right after you ace this refresh course.