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IntelliJ IDEA has many common refactoring techniques that are right at your finger tips.
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So we've done a little bit
of refactoring before,
0:00
you know, changing the code just a little
bit to allow for new code to come through.
0:02
Small, little chunks.
0:06
Well let's do one of those.
0:07
In the past, our queue stored songs, but
now we need it to store song requests.
0:08
So let's go ahead and
make that change with the help of our IDE.
0:13
Okay, so
let's navigate to karaoke machine.
0:17
All right let's look
down here at our queue.
0:23
So it's a queue of Songs.
0:28
We want that to be
a queue of SongRequests.
0:32
Okay, so let's refactor that, so
there's actually a menu for that.
0:34
So let's say refactor and
we are going to chose Refactor this.
0:38
Okay, so when you choose Refactor this,
0:47
it shows all the different refactorings
that it can do, and there are a lot.
0:49
What we wanna do here is we wanna
do a type migration, right?
0:52
We're moving it from the songs,
the type Song, to the type SongRequest.
0:55
So let's do that.
0:59
Okay, so it says migrate the type
of field mSongQueue to be,
1:00
and that was in SongRequest.
1:06
And basically, this is any time this
is used, we want to refactor that, so
1:10
let's choose refactor.
1:14
Okay, so it founds some problems, and it's
mainly places where a song's coming out,
1:17
so let's go ahead and let's choose ignore.
1:21
Okay so that has happened now.
1:24
And now you'll notice,
1:26
see how over here there is a red
squiggly line on different things?
1:27
It means that there's errors, and there's
definitely an error on our file, and
1:31
it's also up here it's
been red squigglied.
1:34
and in our browser up here
it's been red squiggly lined.
1:37
So let's go ahead and in order to find
errors, and over here on the right too,
1:39
there's some, right?
1:44
So in order to find errors, if we pres F2,
it will move to the next error.
1:45
Let's move to the next error, okay,
so this is a really clear one here.
1:50
What's happened here.
1:53
is it's pulled out the songRequest,
and it's called it song.
1:54
It's not actually a Song.
1:58
So, we can use another refactoring here.
1:59
So let's go ahead.
2:01
I'm gonna click this one, and
I'm gonna do that refactor this.
2:02
And that was Ctrl+T.
2:06
So refactor this, and I'm gonna
rename this song to be songRequest.
2:08
Look, it was in the list there.
2:14
So, it knows that.
2:16
So I'm gonna call it songRequest.
2:16
Okay.
2:18
Great.
2:19
So it also changed all these entries
down here, which made it look bad, and
2:21
we kinda wanna add something new here.
2:25
So let's go ahead and
use that multi-cursor that we saw, right?
2:26
So this is really cool.
2:30
This is gonna blow your mind.
2:31
So you hit alt+shift and you click where
you want your cursors to be, okay?
2:32
So look, I've got three cursors there.
2:36
All right, cool.
Now I'm gonna type getSong.
2:38
Great.
2:41
So that's correct.
2:42
And we want to add in here, our singer.
2:44
So we'll say, are you ready %s?
2:48
And we'll add the songRequest.getSingerName().
2:51
Cool, and you know what,
that looks a little bit dorky,
2:57
with all that songRequest.
3:01
Why don't we.
3:02
Let's do this.
3:04
Let's highlight this and
then choose Ctrl+T again to refactor this.
3:05
Let's choose extract variable.
3:12
Oh, sorry.
3:18
See the grouping there?
3:19
Extract variable.
3:19
Okay?
And let's replace all three recurrences.
3:22
Boom, so see there it did.
3:25
It pulled out song, and
it knew I called it song.
3:26
Pretty great.
So I'm
3:28
gonna request that getSong() song, perfect.
3:29
Awesome.
So we have that working.
3:32
All right, so
let's go take care of the other errors,
3:34
cuz obviously there's still some.
3:36
This will go away once we get it.
3:38
So let's press F2, here it is.
3:39
And if we put our cursor in here,
3:42
you'll see the intention
action shows up and it's red.
3:44
And that means that it has
an error that it knows about.
3:46
So if I press alt+enter, it's going to say
make 'promptSongForArtist' return a Song.
3:49
And that's exactly what we want,
so let's have it do that.
3:54
Cool.
So that's working now and see,
3:57
the signature has changed.
3:59
So let's go and hit the next error,
cuz there's still one.
4:00
Okay, so now.
4:03
What's happening here is, it's pulling
a SongRequest out, but we just changed it.
4:05
So, let's change that as well.
4:09
Let's go ahead and
4:12
press Alt+Enter here, and let's change
variable artistSong to be a Song.
4:12
Perfect, okay.
4:18
Now there's a new bug.
4:20
We're adding a Song to a queue that
expects to have a SongRequest.
4:21
So we need to build
a SongRequest Item, right?
4:27
So let's go ahead and before all of this
happens, let's go ahead and say String
4:29
singerName equals promptForSingerName.
4:36
And we'll just make a new function here.
4:41
Okay.
And it's definitely complaining about it.
4:44
Let's see what is suggested.
4:46
So, again, I can press Alt+Enter,
or I can click this over here.
4:48
Oh, it says create method
promptForSingerName.
4:52
That's totally what we want.
4:54
Hey, look at that, it knew that
it was a string from the context,
4:56
what I was asking for.
5:00
Awesome.
5:02
So, let's go down here and we will say
5:02
system print.
5:08
We're gonna print out.
5:12
Actually, we just want to have print.
5:13
Enter the singer's name.
5:16
>> Cool.
5:21
And we wanna just return whatever
comes back from the read line.
5:22
Look, we've been doing it here, readLine.
5:26
Cool.
5:29
Oop, there's an error, what's it saying?
5:30
It says oh yeah,
remember those throw IO exceptions.
5:32
So let's go ahead and we'll do Alt+Enter
and add exception to the method signature.
5:34
Boom.
Perfect, right?
5:39
Great.
5:41
Now we can add that to
the new SongRequest.
5:42
So one thing else that we could do,
we can go back to where I defined this.
5:44
So if I put my mouse here,
or my cursor here,
5:48
and I press command b,
we'll go to the definition of it.
5:51
Cool.
5:55
Awesome, and
it shows us the only usage is right here.
5:55
That's great.
5:59
So now in this mSongQueue
we can say new SongRequest or
6:00
new object, and that takes
a singer name and an artist song.
6:06
Perfect.
6:12
Cool, now everything's happy.
6:14
Look, the red squigglies are gone.
6:15
Hey, you know what?
6:18
Why don't we stop someone from putting the
same song by the same singer in the queue?
6:19
Let's extract that new song
request into a variable.
6:23
So let's go ahead in here.
6:26
I'm gonna highlight this and
I'm gonna do Ctrl+T.
6:28
Let's extract that into a variable.
6:30
Perfect.
6:34
And it's got some suggestions.
6:34
I think we'll got with songRequest.
6:35
This ones a little bit weird, but
you'll get used to it the more you use it.
6:38
One thing that you want to do so,
the song queue.
6:42
We know the song queue has
method called contains.
6:44
And we're going to see if it
contains the song request.
6:47
Now, that returns a boolean.
6:53
So in this editor,
6:56
if you press a dot afterwards, it suggests
things that you could wrap it with.
6:59
And we want to wrap it with the if.
7:03
Right?
We want to say if the song queue
7:05
contains this request let's do that.
7:07
Cool.
So it wrapped it in an if, and
7:09
it gave us the parens there.
7:11
So it's kind of a backwards
way of thinking of it.
7:13
But when you're kind of processing things,
7:15
that is actually the way you thought
about, right, like it contains it.
7:17
So, if it contains it.
So it's an interesting approach.
7:21
So we're gonna use
a printf statement here.
7:23
So we use souf And we're gonna print F.
7:25
We'll say %n%n, whoops.
7:29
%s already requested.
7:33
%s.
7:38
And we'll put in the singer name,
and the artist song.
7:42
And since we're in a choose case,
we don't want to continue through this, so
7:50
we can break out of the choose case there.
7:54
Awesome, so let's go ahead and do Ctrl+R.
7:57
Cool, there we go and
8:05
if I try to choose, oh,
here's the singer's name, that's Craig.
8:06
And if I choose that Journey song, Don't
Stop Believin', and I try to do it again,
8:11
which I've been known to do,
I'm gonna choose the Journey song here,
8:16
Don't Stop Believin'.
8:22
It says whoops, Craig already requested
the song, Don't Stop Believin'.
8:24
Also, I guess we need to add
a new %n in here too.
8:27
We forgot that.
8:29
Awesome.
8:31
So, now I just wanna make sure that
you notice that we're using contains.
8:34
And that is making use of
the equals method that we made.
8:38
And one thing to remember is that
SongRequest is not the same one that's in
8:41
the queue, right?
8:45
We made a brand new one.
8:45
It's actually equal by our
definition of sameness, and
8:47
this sameness is the way that we
define things in the equals method
8:50
in the hash code, on the song request and
the song.
8:53
Pretty cool, right?
8:57
Awesome.
So we are done-zo.
8:58
>> I know, I know.
9:03
You just earned like ten
more dunk tank balls.
9:04
Did you feel how much
the IDE had your back?
9:07
It's looking out for you, and
it really wants you to succeed.
9:09
Did you see how it was stating things that
you most likely didn't understand before
9:12
kicking off onto your job adventures?
9:15
But now, you're able to intelligently
respond to its prompts.
9:18
I hope you're feeling good about yourself,
because that was really impressive.
9:21
All right, so
9:25
I'm really excited to show you the next
advanced tool, which is the debugger.
9:26
Get ready.
9:30
Right after this exercise.
9:30
Oh, and by the way, you're going
to need those changes we made for
9:32
the exercise, so
I hope you were following along.
9:35
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