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You have completed Java Objects (2016)!
You have completed Java Objects (2016)!
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Let's create our first method, a getter.
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Okay so we've fixed our problem with
restricting changes to our character name,
0:00
but it's a little too restrictive.
0:05
It can't even be accessed from
outside the class itself.
0:07
We want to allow consumers of our objects
to still be able to see the value,
0:09
even if they can't change it.
0:13
So how do we let them get the value then,
you ask?
0:15
Great question.
0:18
Well the answer is we build
a method that exposes a value.
0:19
You've used methods before but for
instance on the console object use
0:23
the print F method or on strings
we use the two lower case method.
0:27
Now remember what I said that developers
modeling the real world objects focus on
0:31
two main characteristics
which are state and behavior.
0:35
Well fields usually are used
to express that state and
0:38
its methods help us to
express that behavior.
0:41
So, therefore you can kind of think of
fields as characteristics about your
0:44
object and methods as the verbs or
actions that your object can perform.
0:47
So, just like how you've use methods on
objects before, like string contains or
0:51
integer percent, it's time that
we learn how to write our own.
0:55
Okay, so let's do this.
0:59
Let's add a method to our
object that behaves like this.
1:00
When the method is used or
called it will respond with or
1:04
return to the calling code.
1:08
The value of the private
field character name.
1:10
Now defining a method is pretty similar
More to the way that we define a field.
1:14
They also have access modifiers.
1:18
So let's come here.
1:21
So when I come in here and
1:22
say we definitely we want
this to be public right.
1:23
We want this to be accessible,
that's the point of what we're doing.
1:25
So we'll start with public and now,
1:27
we need to define what type of data
will be returned from this method,
1:30
meaning when I call this method, what
type of answer will I get back from it.
1:35
For instance, let's look at one.
1:39
So if we look at the method
string.contains,
1:40
remember you use that to find
out if something's in there.
1:43
So that is definitely a public method,
right.
1:45
We are using that, and
it returns a Boolean okay.
1:48
So we said that our method was going
to be returning a string, right?
1:52
It's the character name.
1:57
It's a string so so we say, public string.
1:58
And next is the method name so
we're going to get the character names so
2:03
getCharacterName.
2:08
Now, here's the part that makes it
different than the field definition.
2:10
Look, it looks pretty similar, right?
2:13
What we're going to do is we're
going to open parentheses
2:15
stating that this is indeed a method and
it's expected to be called.
2:18
So, here is where you
would define parameters,
2:21
that's if your method needs it.
2:24
So, if we come back to the string contains
method, so it's a public Boolean that
2:25
contains is the name of the method and
again it opens up its parentheses.
2:30
And it needs to know, a parameter we pass
in the string containing words right?
2:35
Remember we did that.
2:41
So back at our example of contains it
needs you to specify what you're looking
2:42
for the contains method
takes a string argument.
2:46
So it's a string of the matching
text that you're looking for, right?
2:50
It specifies that parameter list.
2:56
We'll go over these in a bit but currently
our method doesn't need any parameters.
2:58
So we'll just go ahead and close it and
then we'll start our methods body.
3:01
So it's opening up a new scope and I'll
write right away to put the closing brace.
3:07
So you see all of the editor lines up
the braces, it's really nice this way.
3:14
So now if I come here, I know this is the
class scope and here is this method scope.
3:17
It's a nice way to make sure that
everything's lining up in one class.
3:22
Okay, back to our method.
3:26
In this scope here in this code
block we can write whatever we want.
3:28
In here we can write whatever code the
method should perform when it's called.
3:33
Finally, what should happen is,
3:38
it should return a value of its
expected type, which is string.
3:39
So it's going to use the keyword return.
3:44
And we're going to return
the characterName, right?
3:49
And the character name is
a string characterName.
3:53
So here's the characterName.
3:57
It's going to return this and because it's
in the scope right it's in this class
3:59
scope it has access to this
even though it's private.
4:03
The prefix of get here is part
of a very common pattern.
4:07
It's called a getter, this pattern
of getter for a specific field
4:12
is to name them with get followed by
the name of the field just like we did.
4:17
GetCharacterName so
you can see it's get and
4:22
then character a name and it's getting
this private field character name here.
4:27
So methods that are used to change
the state of these objects or
4:31
set a field value
are prefixed with set and
4:34
those are called of course setters so
together these getters and
4:37
setters are often referred to as
properties in other languages.
4:41
They'll become very common practice for
you in your job adventures.
4:46
Okay, so
now let's flip back to the example.
4:49
I'm gonna go ahead and before we do that,
I'm gonna get rid of this comment here.
4:52
I wanna save this file, and let's
flip back to example and take a look.
4:56
So we know that the code in here doesn't
compile remember it wasn't compiling,
5:01
so let's go ahead.
5:04
Let's get rid of this Darth Vader cuz
we're not gonna change that anymore,
5:05
it's private.
5:08
But now, instead of accessing the private
field character name, let's try to access
5:10
the public method, getCharacterName,
and we're going to call that method.
5:16
So there's some parens I'll put
this down in a new line in here.
5:20
This is highlighting, this is this, okay.
5:24
So we're going to call the method,
getCharacterName and
5:27
that's going to return the method.
5:30
So let's go ahead and
let's compile it and run it.
5:32
I forgot to save it important note
there see the little red dot.
5:37
So compile it and run it.
5:41
Boom we got it, it's back.
5:44
So again the method was called and
our code inside of that method.
5:46
This method body here was run and we
returned the private field characterName.
5:51
And that's definitely more like how
things work in real life, right?
5:58
People can't just go changing
the character on these pez dispensers and
6:02
now we are clearly communicating that
reality because we haven't added a setter
6:05
we've only add it together so
nobody can set that.
6:09
Now, one thing you're probably wondering
is well, we can't change it at all,
6:13
right, it's always going to be Yoda.
6:18
That's a good point.
6:21
Let's tackle that next awesome
job modeling the character.
6:22
Now it can't be changed only retrieved.
6:25
This is a very common pattern
used to express how you'd
6:28
like people to interact with your object.
6:31
We'll run through it a couple more
times in the course just to make sure
6:33
that it's sinking it.
6:35
So we left another problem in there,
didn't we?
6:37
Every single Pez dispenser that we
create is gonna be a Yoda character.
6:40
That's certainly gonna bum out some kids
who want a Teenage Mutant Ninja Turtle or
6:43
an Elsa version, and for
sure sales are gonna plummet.
6:46
Let's do a quick exercise to make sure
that we got this private keyword and
6:50
getter method thing figured out, and
6:53
then we'll fix this Yoda only
situation that we got ourselves into.
6:55
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