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‫Instructor: Hi.

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‫Within this lecture we're going to continue deep diving

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‫into classes because they're very important as you can see.

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‫And we're going to learn about access levels,

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‫accessibility levels.

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‫Okay.

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‫So we have these keywords over here like protected, public.

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‫So we didn't pay attention to them very much before,

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‫but this time we are gonna learn how they work.

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‫So in order to do that,

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‫I'm not gonna mess the previous things over here.

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‫So I'm gonna create a new Java class.

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‫And this time, let's call this something like Simpsons,

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‫and we're gonna create some Simpson objects

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‫out of this class.

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‫So inside of Simpson's class,

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‫we're gonna have some similar things

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‫like we did in the musician's class.

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‫Like we can have a name, we can have an age,

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‫we can have a job, right.

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‫So let me call this age, job,

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‫and maybe you can try with other attributes as well,

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‫but I'm gonna keep it simple.

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‫I'm gonna say generate constructor, choose everything,

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‫and hit okay.

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‫So this will be my constructor.

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‫As you can see, I have the same setup over here

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‫like we did in the musicians.

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‫Now let's create an another method called makeSimpsons.

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‫Okay.

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‫And inside of these methods we are going to make Simpsons.

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‫Of course we don't have to do that.

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‫I'm just doing this in order to be tidy,

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‫in order to be structural.

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‫So let me call the first one Homer

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‫and then I say new Simpsons.

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‫It will ask for a name, ask for an age, and ask for a job.

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‫And as much as remember the Homer Simpson

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‫was a nuclear safety guy.

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‫So I'm going to say nuclear.

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‫And over here it really doesn't have any differences

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‫when we compare it to the musicians right now.

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‫So if you say Homer.age, you can reach the age.

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‫And you can even change it.

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‫Like you can make it 51.

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‫And let me print the age so that we can be certain

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‫that we got to change it once we initialize it.

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‫Okay.

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‫Let me call, makeSimpsons over here

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‫so that it will get executed.

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‫So let me run the emulator,

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‫and of course we will have to track this in our logcat.

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‫So here you go.

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‫We see that 51.

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‫And it means that everything is working

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‫as it's supposed to be.

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‫But let me add public keyword over here.

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‫So what does public mean?

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‫It's actually detectable over here

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‫because it's public by default.

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‫Public means that it can be reached

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‫within other classes as well.

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‫So we are writing string name in Simpsons,

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‫but you can actually change it

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‫or read it from other classes like main activity as well.

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‫But if I do something like this private, okay,

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‫then you will-

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‫I would get some errors

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‫because age has private property right now

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‫so you can initialize it like in Simpson's Homer case,

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‫but you cannot reach it and change it afterwards.

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‫As you can see, it doesn't even compile it.

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‫It says that age has private access in Simpsons.

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‫So if you make your attributes private

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‫then you cannot change it afterwards.

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‫You cannot even read it.

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‫Of course, there are other methods

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‫like getters and setters in order

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‫to have some reading options,

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‫but not writeable options.

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‫We're gonna look into that later on.

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‫So other than public and private,

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‫there are some other key words like protected as well.

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‫So protected means it's protected

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‫and you can reach it from the same class,

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‫but when you do it private,

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‫you can actually reach it from the same class.

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‫But if you do protect it,

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‫you can reach it in the same Java file.

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‫Okay, so if you have class inside of a class

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‫or something like that, then you can reach it

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‫once you define it as protected.

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‫Once you define it as public,

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‫you can reach it from any class.

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‫Once you do it as private,

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‫then you cannot reach it from anywhere else,

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‫but within your same class.

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‫So when you first deal with Android development,

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‫you don't really actually involve with this decision at all.

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‫So it really doesn't matter for you

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‫if you make it protected or private or public.

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‫But once you get into bigger projects,

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‫once you start working, collaborating with other developers

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‫then you should really pay attention to those.

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‫Because if you don't want them to be public,

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‫then don't make it public.

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‫But if you want this to work like this,

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‫like we have seen before,

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‫then you should change it back to the public

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‫and make sure you can reach Homer.age

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‫or Homer.instrument or Homer.name within another class.

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‫Then you should declare it as public.

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‫So this is how you work with accessibility levels

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‫inside of Android development.

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‫So right now we only have one issue to cover

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‫inside of classes subject,

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‫and that is getters and setters.

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‫We're gonna look into that in the next lecture.