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Refactoring
9:38IntelliJ IDEA has many common refactoring techniques that are right at your finger tips.
So we've done a little bit
of refactoring before,
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you know, changing the code just a little
bit to allow for new code to come through.
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Small, little chunks.
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Well let's do one of those.
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In the past, our queue stored songs, but
now we need it to store song requests.
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So let's go ahead and
make that change with the help of our IDE.
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Okay, so
let's navigate to karaoke machine.
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All right let's look
down here at our queue.
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So it's a queue of Songs.
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We want that to be
a queue of SongRequests.
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Okay, so let's refactor that, so
there's actually a menu for that.
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So let's say refactor and
we are going to chose Refactor this.
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Okay, so when you choose Refactor this,
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it shows all the different refactorings
that it can do, and there are a lot.
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What we wanna do here is we wanna
do a type migration, right?
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We're moving it from the songs,
the type Song, to the type SongRequest.
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So let's do that.
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Okay, so it says migrate the type
of field mSongQueue to be,
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and that was in SongRequest.
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And basically, this is any time this
is used, we want to refactor that, so
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let's choose refactor.
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Okay, so it founds some problems, and it's
mainly places where a song's coming out,
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so let's go ahead and let's choose ignore.
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Okay so that has happened now.
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And now you'll notice,
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see how over here there is a red
squiggly line on different things?
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It means that there's errors, and there's
definitely an error on our file, and
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it's also up here it's
been red squigglied.
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and in our browser up here
it's been red squiggly lined.
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So let's go ahead and in order to find
errors, and over here on the right too,
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there's some, right?
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So in order to find errors, if we pres F2,
it will move to the next error.
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Let's move to the next error, okay,
so this is a really clear one here.
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What's happened here.
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is it's pulled out the songRequest,
and it's called it song.
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It's not actually a Song.
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So, we can use another refactoring here.
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So let's go ahead.
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I'm gonna click this one, and
I'm gonna do that refactor this.
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And that was Ctrl+T.
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So refactor this, and I'm gonna
rename this song to be songRequest.
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Look, it was in the list there.
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So, it knows that.
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So I'm gonna call it songRequest.
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Okay.
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Great.
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So it also changed all these entries
down here, which made it look bad, and
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we kinda wanna add something new here.
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So let's go ahead and
use that multi-cursor that we saw, right?
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So this is really cool.
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This is gonna blow your mind.
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So you hit alt+shift and you click where
you want your cursors to be, okay?
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So look, I've got three cursors there.
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All right, cool.
Now I'm gonna type getSong.
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Great.
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So that's correct.
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And we want to add in here, our singer.
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So we'll say, are you ready %s?
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And we'll add the songRequest.getSingerName().
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Cool, and you know what,
that looks a little bit dorky,
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with all that songRequest.
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Why don't we.
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Let's do this.
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Let's highlight this and
then choose Ctrl+T again to refactor this.
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Let's choose extract variable.
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Oh, sorry.
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See the grouping there?
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Extract variable.
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Okay?
And let's replace all three recurrences.
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Boom, so see there it did.
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It pulled out song, and
it knew I called it song.
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Pretty great.
So I'm
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gonna request that getSong() song, perfect.
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Awesome.
So we have that working.
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All right, so
let's go take care of the other errors,
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cuz obviously there's still some.
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This will go away once we get it.
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So let's press F2, here it is.
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And if we put our cursor in here,
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you'll see the intention
action shows up and it's red.
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And that means that it has
an error that it knows about.
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So if I press alt+enter, it's going to say
make 'promptSongForArtist' return a Song.
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And that's exactly what we want,
so let's have it do that.
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Cool.
So that's working now and see,
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the signature has changed.
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So let's go and hit the next error,
cuz there's still one.
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Okay, so now.
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What's happening here is, it's pulling
a SongRequest out, but we just changed it.
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So, let's change that as well.
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Let's go ahead and
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press Alt+Enter here, and let's change
variable artistSong to be a Song.
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Perfect, okay.
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Now there's a new bug.
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We're adding a Song to a queue that
expects to have a SongRequest.
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So we need to build
a SongRequest Item, right?
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So let's go ahead and before all of this
happens, let's go ahead and say String
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singerName equals promptForSingerName.
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And we'll just make a new function here.
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Okay.
And it's definitely complaining about it.
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Let's see what is suggested.
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So, again, I can press Alt+Enter,
or I can click this over here.
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Oh, it says create method
promptForSingerName.
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That's totally what we want.
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Hey, look at that, it knew that
it was a string from the context,
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what I was asking for.
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Awesome.
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So, let's go down here and we will say
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system print.
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We're gonna print out.
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Actually, we just want to have print.
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Enter the singer's name.
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>> Cool.
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And we wanna just return whatever
comes back from the read line.
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Look, we've been doing it here, readLine.
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Cool.
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Oop, there's an error, what's it saying?
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It says oh yeah,
remember those throw IO exceptions.
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So let's go ahead and we'll do Alt+Enter
and add exception to the method signature.
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Boom.
Perfect, right?
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Great.
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Now we can add that to
the new SongRequest.
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So one thing else that we could do,
we can go back to where I defined this.
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So if I put my mouse here,
or my cursor here,
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and I press command b,
we'll go to the definition of it.
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Cool.
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Awesome, and
it shows us the only usage is right here.
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That's great.
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So now in this mSongQueue
we can say new SongRequest or
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new object, and that takes
a singer name and an artist song.
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Perfect.
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Cool, now everything's happy.
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Look, the red squigglies are gone.
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Hey, you know what?
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Why don't we stop someone from putting the
same song by the same singer in the queue?
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Let's extract that new song
request into a variable.
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So let's go ahead in here.
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I'm gonna highlight this and
I'm gonna do Ctrl+T.
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Let's extract that into a variable.
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Perfect.
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And it's got some suggestions.
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I think we'll got with songRequest.
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This ones a little bit weird, but
you'll get used to it the more you use it.
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One thing that you want to do so,
the song queue.
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We know the song queue has
method called contains.
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And we're going to see if it
contains the song request.
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Now, that returns a boolean.
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So in this editor,
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if you press a dot afterwards, it suggests
things that you could wrap it with.
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And we want to wrap it with the if.
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Right?
We want to say if the song queue
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contains this request let's do that.
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Cool.
So it wrapped it in an if, and
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it gave us the parens there.
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So it's kind of a backwards
way of thinking of it.
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But when you're kind of processing things,
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that is actually the way you thought
about, right, like it contains it.
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So, if it contains it.
So it's an interesting approach.
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So we're gonna use
a printf statement here.
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So we use souf And we're gonna print F.
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We'll say %n%n, whoops.
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%s already requested.
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%s.
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And we'll put in the singer name,
and the artist song.
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And since we're in a choose case,
we don't want to continue through this, so
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we can break out of the choose case there.
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Awesome, so let's go ahead and do Ctrl+R.
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Cool, there we go and
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if I try to choose, oh,
here's the singer's name, that's Craig.
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And if I choose that Journey song, Don't
Stop Believin', and I try to do it again,
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which I've been known to do,
I'm gonna choose the Journey song here,
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Don't Stop Believin'.
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It says whoops, Craig already requested
the song, Don't Stop Believin'.
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Also, I guess we need to add
a new %n in here too.
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We forgot that.
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Awesome.
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So, now I just wanna make sure that
you notice that we're using contains.
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And that is making use of
the equals method that we made.
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And one thing to remember is that
SongRequest is not the same one that's in
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the queue, right?
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We made a brand new one.
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It's actually equal by our
definition of sameness, and
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this sameness is the way that we
define things in the equals method
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in the hash code, on the song request and
the song.
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Pretty cool, right?
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Awesome.
So we are done-zo.
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>> I know, I know.
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You just earned like ten
more dunk tank balls.
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Did you feel how much
the IDE had your back?
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It's looking out for you, and
it really wants you to succeed.
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Did you see how it was stating things that
you most likely didn't understand before
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kicking off onto your job adventures?
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But now, you're able to intelligently
respond to its prompts.
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I hope you're feeling good about yourself,
because that was really impressive.
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All right, so
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I'm really excited to show you the next
advanced tool, which is the debugger.
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Get ready.
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Right after this exercise.
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Oh, and by the way, you're going
to need those changes we made for
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the exercise, so
I hope you were following along.
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