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‫All right.

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‫Now that you have seen the theory behind variables and data types, let's actually use them in practice.

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‫And we're going to start with integers, doubles as well as floats.

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‫So let's get started.

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‫First of all, in order to declare a variable, we just use the data type and then we give the variable

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‫a name.

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‫And of course we need to add the semicolon.

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‫So you see here I'm declaring a variable even though I'm not giving it a value, even though I'm not

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‫initializing the variable, which means I'm not assigning a value to it.

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‫So if I now assign a value to it, I can do that after the fact, for example, in the next line.

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‫So here I can assign a value to a variable just by using the variable name.

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‫And now I'm saying at this position I want to store the value of 13.

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‫So here we declared the variable and now we are assigning a value or we are initializing that variable.

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‫Okay, now let's actually write this variable onto our console so we can write the variable using console

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‫right line.

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‫And then in brackets we just use num one here and it will then display num one for us.

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‫So depending on the settings that you have, you will potentially also need to use console to read in

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‫order to keep your console open and running when testing this.

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‫So let's test this real quick and we can see it says 13.

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‫So here this 13 up there.

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‫Okay, so that works.

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‫Now we can display a value.

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‫So let's display something more interesting.

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‫Let's actually display the sum of two variables.

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‫So now we have NUM one which currently is 13.

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‫Now let's create another variable called NUM two.

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‫So I'm going to declare and initialize the value in the same line.

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‫So here we are declaring and initializing the variable in one go we're saying data type integer name

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‫num two is going to be 23.

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‫So now internally for this variable name, numb to it will store the value of 23.

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‫So what we can do now, of course, is apply mathematical operations on it.

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‫So let's just create a new variable called sum and this will now be the sum of NUM one and num two.

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‫And by the way, once I do that, you can see that the underline goes away.

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‫So here, this one here where the number two is never used, you see this green underlining now it goes

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‫away because this green underlining just says that this variable is never used.

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‫So now we are actually using it in this line here.

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‫Okay, so now we have the sum, let's actually print out the sum of 13 and 23 in this bright line statement

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‫here.

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‫Okay, let's do that.

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‫Let's run our program.

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‫And it says 36 because 23 plus 13 or 13 plus 23 is going to be 36.

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‫All right.

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‫That's great.

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‫But now I would like to actually see what I am doing there.

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‫Therefore, I can use this concept of concatenation.

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‫Let me show you real quick.

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‫So here, concatenation where I'm using.

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‫The number one.

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‫I'm saying number one on the console plus.

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‫Which means it's going to display num one with the actual value of none one.

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‫So this variable here then I'm saying in the text the empty space plus empty space numb to.

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‫So now I'm using the value of num two here plus num two.

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‫Is some.

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‫So this looks a little complicated.

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‫Let's break it down in a second, but let's first run it.

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‫So you see, number one is 13 plus.

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‫Number two is 23 is 36.

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‫So here I would need an empty space to.

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‫Indicate that a little better.

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‫So let's do that once again.

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‫Now it says number one, 13 plus number two.

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‫23 is 36.

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‫So let's use a more simple example where I'm just going to use the console right line.

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‫You can just enter c w and press double tap, then it will give you the code automatically, which really

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‫helps.

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‫So now I'm going to just say no one is and then an empty space plus num one.

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‫So what I'm doing here is I'm just saying, please use this text that I have here, plus whatever is

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‫behind this num one.

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‫And now even though this is an integer, this console right line method will be smart enough to understand

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‫that it can convert this into a string, which means it can convert it into a text format as well.

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‫Because internally this will still be a number.

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‫Right?

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‫But right now and we'll be smart enough to make it a text because this just displays text, right?

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‫So if we run it, it says NUM is 13 and actually it should be NUM one is 13.

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‫Okay.

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‫So this will now display NUM one.

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‫But what we're doing in this line here is we are displaying num one plus num two is sum and here we're

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‫just giving out the value so that we know what we are actually calculating in order to know whether

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‫what we're doing is correct.

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‫So the concept of adding strings together and also adding numbers into strings together is called concatenation.

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‫So here this plus is not an actual sum that we're building.

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‫So we're not actually operating a plus here.

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‫We're not adding something.

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‫We are just saying this play this text and then add to this text.

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‫This text, whatever detects behind it is.

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‫Then add to that text that you had so far, this text over here and so forth.

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‫So that's what's happening here.

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‫So we're not actually calculating anything here, even though we're using a bunch of pluses.

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‫Okay.

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‫So that is concatenation.

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‫Now let's look at how we can create multiple variables at once, meaning in one line of code.

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‫Therefore, we can use this code here saying something like data type.

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‫Then the name of the first variable comma.

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‫Name of the second variable comma, name of the third variable.

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‫So here we are separating them with a comma, and then we're ending this statement with a semicolon,

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‫as always.

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‫So this is just a quicker way to create variables.

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‫And usually you would do that at the beginning of your, in this case, method or even class, depending

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‫on where you want to use it.

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‫And we're going to look into when to use what later on.

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‫So here I'm putting it at the top, which will allow me to make sure that I have all of my variables

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‫at one spot, at least the declaration of the variables at one spot.

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‫I can, of course, then later on use them and overwrite them.

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‫So for example here when I created this variable NUM two and I set it up as 23, it had the value of

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‫23, of course, but now I can override it by using them two, and I could assign a value of 100 to

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‫it, for example.

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‫Now let's run this code and see what's going to happen.

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‫So here it says, number one, 13 plus number two, which is 100, is going to be 36.

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‫But that's not correct.

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‫Right, because 13,100 is not 36.

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‫That is because we did the actual calculation here.

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‫Then we change the value of number two and then we used it in this line here.

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‫So you have to be super careful with this approach when you're using it.

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‫So let's now actually cut this line out here and use it down there.

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‫So now it will give us the correct value, which should be 113 here as the result.

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‫And you can see 13 plus two is 130.

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‫Okay, now let's do the same thing with doubles.

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‫So I said we would also use doubles, which is a different data type.

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‫So if you want to use doubles, you just need to use the double keyword and then you give it a name.

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‫So I'm going to call this double one and it will be the value of 3.4 or 1415.

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‫I could of course have also called this one PI and then I'm going to have another double, which is

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‫going to be something like 5.1 or something like that.

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‫Nothing too complicated.

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‫And now I'm going to divide.

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‫All right, so let's use this new variable that I'm going to call def double dividend.

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‫So it's going to use D one and divided by D two and it's going to store it in this variable here.

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‫So I'm just going to print out the result into my console saying DX one divided by DX two is.

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‫And then I'm going to use the div like so.

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‫So now let's see what 3.14 divided by 5.1 is going to be.

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‫And we can see it's 0.615 and so forth.

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‫So it's a very long number here.

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‫So you see this double can hold a very long number, which is great.

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‫Now let's look at the same example with floats.

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‫So here I'm going to use float and I'm going to use the same variable value.

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‫So also 3.1415, whatever.

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‫And then I'm going to use this float F two in order to also hold the value of 5.1.

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‫So now I'm running into an issue here because I'm trying to assign a value here, but it doesn't accept

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‫it.

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‫I'm getting an error and that is because there's 3.1415 by default is considered to be a double by our

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‫program.

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‫So things that we are trying to assign a double value to a floating point variable, which doesn't work.

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‫So what we can do now is we can add an F here and this says, okay, this is a floating point number.

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‫So now we can add the F here as well.

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‫And now we're specifically stating, okay, this 5.1 is not a double, but it's a floating point value.

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‫This was just internally decided at one point when the programming language was developed, and that's

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‫the end result that we have.

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‫So we need to add the F if we are working with floats, because otherwise it will think that we're working

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‫with it double like we had seen here.

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00:10:44,500 --> 00:10:47,530
‫Okay, now let's do this division as well.

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‫F div is going to be f one divided by f two.

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00:10:53,410 --> 00:10:56,830
‫And now let's also write this onto our console.

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‫So here F one divided by F two is going to be f div and let's run it.

153
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‫And we can see that the result is rounded here.

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00:11:08,920 --> 00:11:13,360
‫At this point, it's around the two of four and it is not as precise.

155
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‫So floating point values aren't as precise as doubles.

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‫So if you need a high precision, then you need to use doubles.

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‫If you need to a low precision, then a float is the better choice because it will require less memory.

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‫This is very, very important when writing efficient software.

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‫So make sure to only use the type of variable that will hold exactly what you are intending to do with

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‫the variable.

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‫So if you only need whole numbers, then just use integers.

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‫If you need super long numbers, then use longs.

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00:11:47,010 --> 00:11:55,350
‫So something like along my long num and then you can assign a long number to it.

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‫So this is even too long?

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00:11:57,750 --> 00:11:58,580
‫For a long.

166
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‫But something like this will be good enough.

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‫So for integers, for example, my long int it wouldn't be able to hold this long number.

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‫So you see here it doesn't accept it.

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‫It says represents a 64 bit signed integer but cannot implicitly convert type long into int.

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‫So now because the number is so long, it thinks it is long, but we're trying to assign it to an int,

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‫so that's why it doesn't work.

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‫So that's something that you have to be aware of when creating variables.

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‫So not something that you need to take into consideration also is that you have to be careful when you're

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‫working with different data types.

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00:12:40,320 --> 00:12:47,520
‫So let's say we want to divide, let's create a new variable here called double.

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00:12:48,310 --> 00:12:56,750
‫And I'm going to call this 1di div, which will use a double and an integer to divide.

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00:12:56,770 --> 00:13:00,250
‫So let's divide D one by num one.

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‫Let's see what's going to happen here.

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00:13:03,700 --> 00:13:06,970
‫So let's write that onto the console also.

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00:13:07,510 --> 00:13:10,540
‫So here this will be the one divided by num.

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00:13:10,540 --> 00:13:14,470
‫One is d i div.

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00:13:15,260 --> 00:13:15,620
‫Okay.

183
00:13:15,620 --> 00:13:16,160
‫So.

184
00:13:16,880 --> 00:13:25,610
‫You see here that now, even though I divided and double by an integer, I still got a double here because

185
00:13:25,610 --> 00:13:27,320
‫that's what I stored here.

186
00:13:27,620 --> 00:13:29,540
‫So this D diff is a double.

187
00:13:29,720 --> 00:13:33,110
‫Now let's do the same thing, but this time with an integer.

188
00:13:33,830 --> 00:13:40,400
‫So I'm going to call this one d div int and it will in fact hold an integer.

189
00:13:41,060 --> 00:13:45,320
‫So now I'm dividing a double by an integer and you see I get an error.

190
00:13:45,350 --> 00:13:49,890
‫Cannot implicitly convert type double to int an explicit conversion exists.

191
00:13:49,910 --> 00:13:51,230
‫Are you missing a cast?

192
00:13:51,230 --> 00:13:58,280
‫So we could now cast and explicitly convert it, but that is something that we are going to see later

193
00:13:58,280 --> 00:13:58,700
‫on.

194
00:13:59,420 --> 00:14:05,240
‫So be aware that you have to be careful with the data types that you are using and this is something

195
00:14:05,240 --> 00:14:07,940
‫that you will over time get from experience.

196
00:14:07,970 --> 00:14:09,830
‫Now, here, this is no problem, right?

197
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‫Because we are in full control of the data that we are getting.

198
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‫But it's going to be a different story if you are suddenly getting the data from an external source

199
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‫where you get the data from a database, for example, from the cloud, and then you wouldn't have full

200
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‫awareness of every single variable.

201
00:14:27,950 --> 00:14:34,610
‫You would just get the data and you want to have it in a certain format, but you can not always be

202
00:14:34,610 --> 00:14:37,400
‫100% certain that you get it in the format you want.

203
00:14:37,400 --> 00:14:41,420
‫So that's something that you will learn once you will become more experienced.

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‫And we are going to look at data basis in a later chapter as well.

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‫All right.

206
00:14:47,000 --> 00:14:48,230
‫That's it for this video.

207
00:14:48,230 --> 00:14:53,900
‫So now you should have a better idea of how to use variables and data types specifically int, float

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00:14:53,900 --> 00:14:54,530
‫and double.

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00:14:54,770 --> 00:14:56,000
‫See you in the next video.