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‫Instructor: Hi.

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‫Within this lecture we are going to continue

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‫with the variables and most popular data types

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‫like we have seen double, float, and integer, and long.

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‫We are going to see strings and some other types as well.

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‫So for example, we have seen what happens when

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‫we divide double by double or integer by integer.

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‫Let's create a double called pi,

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‫and this will be equal to 3.14 of course

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‫and let's create an integer for example

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‫for our radius and calculate a circumference of a circle.

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‫Okay? So for example, I have my pi, 3.14

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‫I have my radius as five.

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‫So do you know the equation of circumference?

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‫It's two multiplied by pi multiplied by radius, right?

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‫So what happens when we multiply an integer with a double?

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‫Now we're gonna find out about that, aren't we?

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‫Let's call System.out.println one more time

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‫and try to multiply 2 by pi by r.

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‫And I suggest you pause the video

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‫and try to do it on your own

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‫with these kind of little exercises okay?

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‫So let me do it and let me run it.

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‫And you will see it's 31.4,

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‫so don't worry about this 000002 things

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‫like if it's a very small decimal

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‫it's not your fault, it's just how actually

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‫Android handles how Java handles the decimals.

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‫So it's not very important.

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‫It won't mess with your calculations in real life examples

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‫but as you can see we got a double out of this.

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‫So we got 31.4 as we expect.

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‫So if we just multiply a double by an integer as

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‫as we would expect, it gives out the result as a double

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‫and it's actually better for us because we can

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‫see the decimals at this point.

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‫So if you need decimals, make sure you are working

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‫with doubles, at least in a single parameter

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‫of an equation like this so that you can get

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‫specific results out of that.

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‫So let me move on to some other examples from here.

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‫I believe this is sufficient for us right now at least

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‫about numbers because we have so many data types

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‫and we are going to do a lot of examples with numbers later

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‫on as well.

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‫So let me talk about strings.

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‫We have briefly talked about that before

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‫right? We have talked about that

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‫this is a text.

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‫So let me do an example.

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‫Just write String with an upper case S

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‫and give some name afterwards.

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‫Like this is an object name like, "name",

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‫or, "myString", or "myName", or anything you want.

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‫Okay let's go with name

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‫for example and open this quotation marks

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‫and between the quotation marks, write your text.

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‫So you can do it with your own name.

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‫I'm gonna do it with James Hatfield.

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‫So I'm going to call this name, I'm going to

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‫create another string, which is surname, which is Hatfield.

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‫Okay? And don't forget with semi-colons at the end

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‫and now I'm going to print name

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‫and now I'm going to print surname.

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‫Just beware that I'm not putting

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‫any double quotations, quotation marks

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‫in the System.out.println over here.

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‫I'm just writing surname or name

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‫because I can refer to that variable right now.

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‫So this is good.

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‫So if I run this, of course it will print

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‫out James Hatfield one by one over here.

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‫So now I have these variables

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‫I can do whatever I want to do with them.

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‫For example, I can create a new string out of those.

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‫Like I can just create a full name

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‫and some name and surname together like this.

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‫So what happens when I add one string to another?

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‫So let me try to print line

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‫that as well so that we can see the results in the logs.

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‫Here you go.

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‫As you can see, it added them side by side.

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‫So we can see the name and surname together like this.

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‫So of course you're thinking about how to put a space

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‫between name and surname right now it's very easy.

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‫You can do like this.

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‫So, name plus a space over here and plus surname.

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‫So if I run this, then I will see, "James Hatfield".

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‫Now I can use those variables in wherever I want

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‫at this point on, right?

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‫So this is strings, this is very basic.

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‫This is just a text.

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‫So before we have learned about numbers, they were integers

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‫and floats and doubles and longs.

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‫Now we have learned about strings.

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‫Now we wanna move on to booleans.

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‫So this is a type as well.

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‫So what kind of a data type is this?

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‫So boolean is a true or is a false.

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‫So they have only two values

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‫actually it's either true or false.

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‫So how do we use them?

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‫So let's create a boolean

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‫and create it like this boolean with small b.

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‫And then you can give it a name.

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‫For example, in a real life example would be a game

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‫like for tracking if character is alive.

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‫So if it's true, then my character is alive

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‫and if it's false, then my character is dead.

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‫So maybe I can keep track

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‫whether my character is alive or not with a variable.

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‫I can change it anytime I want.

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‫Like this:

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‫Let's print those out and let's see

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‫if we can see the false over here.

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‫Here we go.

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‫As you can see, it's the most basic data type of all.

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‫So it's either true or false.

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‫There isn't many thing to talk about it right now

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‫but later on we are going to see a lot

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‫of usages of booleans as well.

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‫So once I create a string

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‫or once I create a variable, I can change it, right?

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‫For example, I have changed name to be Lars

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‫and now if I print name, I will see Lars as you can see.

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‫But I cannot do that.

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‫I cannot change name to be 40 like this,

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‫because I have defined name as a string, not an integer.

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‫As you can see it gives me an error.

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‫I'm expecting a string and you are giving me an integer

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‫it says. So whatever you have specified first

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‫you have to do that later on as well.

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‫So let me comment this out and go up and over here.

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‫For example, we have double z.

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‫Now can I do that?

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‫Can I say this is a four?

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‫Yep, I can do that actually.

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‫It doesn't mean it's necessarily an

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‫integer right now because it's perceived as a double.

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‫But if I do that

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‫as you can see right now, it's giving me an error.

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‫It's not exactly a double.

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‫It's a string it says.

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‫Whenever you do 4 it, it just thinks it as 4.0.

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‫Okay? So it's okay

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‫but turning it into a string, it's not okay.

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‫So that's it for the most basic ones.

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‫These are the data types that you're going to

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‫need when you try to learn the other concepts

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‫of Java in the following lectures.

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‫So make sure you follow along with the next lectures

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‫in order to comprehend all of those things in a better way.