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‫Instructor: Hi, We're going to deep dive

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‫into the classes in this lecture

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‫and we're gonna learn a very important concept

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‫called constructor, okay?

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‫So far we have created our own object

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‫but there are some better ways to deal with this kind of

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‫situations in Java at our under development.

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‫So in order to learn about constructor,

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‫I'm just gonna create it.

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‫So if you come over here and right click and say generate

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‫or if you come over here to coding menu and say generate

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‫it will give you a menu.

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‫And as you can see

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‫we have the constructor in the first place.

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‫Now we are looking for constructor

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‫because that's what we are going to learn

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‫and deep dive in this lecture.

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‫As you can see, once we come over here

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‫it will ask what kind of properties that we want to include.

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‫Hit shift and select everything and hit enter or okay.

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‫And as you can see, it created our first constructor.

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‫So what is a constructor anyway?

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‫Yeah, it constructs some object, but what does it really do?

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‫So if you create that, that constructor,

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‫and if you come over here,

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‫now you will see you're getting some kind of an error.

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‫So what is the error over here?

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‫So we are creating an instance,

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‫an object out of this Musicians class.

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‫Right?

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‫So when we create a new instance or a new object

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‫constructor is the first method to be executed.

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‫This is the first thing happens

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‫right after you create your own object.

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‫And in this case, as you can see,

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‫we are doing some kind of initialization like

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‫this.name = name.

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‫So let me print out something over here,

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‫so we can understand it better, right?

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‫So as you can see, we have all this codes here.

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‫this.instrument = instrument

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‫this.age = age.

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‫And it doesn't make sense when you first look into it.

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‫However, it actually makes sense.

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‫Since we have these properties inside of our class.

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‫Now we can ask for an input

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‫as a parameter inside of our public Musicians method.

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‫And then we can make this.name

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‫equals to that parameter.

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‫You don't know what this is.

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‫I'm going to explain it, don't worry.

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‫Right now focus on this.

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‫We're going to take some parameters

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‫and we're gonna make it equal to the properties

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‫that we have defined inside of our class.

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‫Now you can change it if you want, like instrument2, age2,

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‫and you can actually differentiate these names

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‫from these parameters.

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‫So name over here, this.name refers

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‫to the attributes of this class.

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‫So this is, these are called attributes

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‫and these are called parameters.

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‫So we are asking for parameters

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‫inside of any other class inside a main activity

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‫and developer gives some instrument2, name2, age2

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‫And by saying this.name, we refer to the name,

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‫instrument, and age of the class.

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‫So this refers to the class,

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‫this refers musicians.

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‫You can name them, name, instrument, or age

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‫and you can name them whatever you want.

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‫But this is the main convention.

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‫They have the same names.

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‫So you can do it like this.

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‫Let me call this constructor called

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‫and let me come over here

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‫and see what kind of error we have and as you can see

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‫Musicians now asking for parameter

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‫and we don't give,

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‫if we don't give any parameters, it won't even work.

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‫Now we have to give age, instrument and name

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‫rather than giving those values afterwards.

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‫When we say new Musicians, it'll ask for a name

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‫and as you can see, it actually gives us some hints as well.

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‫Once we hit double quotation marks,

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‫now I gotta say James, Guitar and 50,

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‫and it'll just make it equal to James, Guitar and 50.

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‫Now if I say james.age one more time

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‫I can reach that value as well, right?

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‫So let me try to print this out.

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‫I will say james.instrument, for example.

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‫It'll print out guitar.

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‫Of course, in order to make this work,

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‫I have to call this makeMusicians Method

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‫inside of any other method like onCreate

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‫or any other method that will be executed

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‫without my intervention.

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‫So let me call this inside of onCreate methods,

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‫like here, okay?

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‫And this will be called,

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‫and we are gonna create an instance,

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‫and then we are going to print out the instrument

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‫of that instance.

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‫So let's follow this.

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‫Here we go.

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‫Now constructor called because we created James,

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‫and then after that

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‫the instrument of James got printed in the logs.

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‫So this is how you work with constructors.

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‫This is how you work with classes generally.

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‫So let's stop here and continue within the next one.