1
00:00:00,360 --> 00:00:01,110
Welcome back.

2
00:00:01,110 --> 00:00:06,420
In the last week, we created our first variables and we used immutable variables.

3
00:00:07,020 --> 00:00:13,140
And we also saw what an immutable variable is, how immutable variable.

4
00:00:13,530 --> 00:00:16,950
Now what I'm using here is a comment.

5
00:00:17,130 --> 00:00:18,540
So this here is a comment.

6
00:00:18,820 --> 00:00:26,190
This is code that will not be considered by the compiler, so it will not have any influence onto our

7
00:00:26,370 --> 00:00:28,110
application or our program.

8
00:00:28,440 --> 00:00:34,200
It's just a comment that helps me to understand what my code does, and it also helps other developers

9
00:00:34,200 --> 00:00:35,820
to understand what code does.

10
00:00:36,180 --> 00:00:42,480
And they are really great to not only understand what code does, but they are also great in order to

11
00:00:42,660 --> 00:00:44,080
know what would you need to do.

12
00:00:44,100 --> 00:00:50,490
So, for example, if you had to do, then you know, OK, at this point, I will need to add a functionality,

13
00:00:50,490 --> 00:00:53,700
add new functionality, for example.

14
00:00:54,150 --> 00:01:00,180
And this is great, because then you can go to your To-Do window here at the bottom and you can very

15
00:01:00,180 --> 00:01:02,200
quickly find this.

16
00:01:02,220 --> 00:01:04,800
So let's say I go to a different document.

17
00:01:07,890 --> 00:01:09,540
And I go to my.

18
00:01:11,160 --> 00:01:15,840
Main activity and now in my to do, I can simply.

19
00:01:17,310 --> 00:01:22,530
Fight mode to do element and directly goes over to this spot.

20
00:01:23,040 --> 00:01:29,520
And this is amazing because it really helps me to navigate through my files.

21
00:01:29,670 --> 00:01:34,500
In this case, it's super easy because I only have two documents, but once I have many different documents,

22
00:01:34,860 --> 00:01:36,180
this will come in very handy.

23
00:01:36,780 --> 00:01:43,830
Other than comments with just two slashes, we can also create multi-line comments by by using a slash

24
00:01:43,830 --> 00:01:45,740
and then a asterisk.

25
00:01:46,050 --> 00:01:46,260
OK?

26
00:01:46,800 --> 00:01:47,340
And with.

27
00:01:48,610 --> 00:01:56,380
That's it automatically creates the closing comment or the ending comment, which is an asterisk with

28
00:01:56,710 --> 00:02:00,550
a slash, so everything in between here will be a comment.

29
00:02:00,760 --> 00:02:04,180
This is a comment.

30
00:02:04,840 --> 00:02:07,570
So this is a multi-line comment to be precise.

31
00:02:07,570 --> 00:02:10,539
Multi line comment.

32
00:02:12,330 --> 00:02:18,060
All right, so just so you know how you can create comments and what they do, so they don't have any

33
00:02:18,060 --> 00:02:23,310
impact onto our program, on the execution time, on the compiling time.

34
00:02:23,430 --> 00:02:26,580
None of that is just for us as a developer.

35
00:02:27,720 --> 00:02:30,630
All right now, let's have a look at other variable types.

36
00:02:30,960 --> 00:02:35,160
I told you that Caitlin is a typed language.

37
00:02:35,580 --> 00:02:44,940
This means but every variable is of a specific type and type inference as a concept that allows us to

38
00:02:45,240 --> 00:02:51,120
just assign a value to a variable and Kotlin will know of which type that variable will be.

39
00:02:51,570 --> 00:02:54,510
So, for example, it knows that this is of type string.

40
00:02:55,020 --> 00:03:03,930
If I create another variable, let's say my h and I assign 31 to it, then this my h variable will be

41
00:03:03,930 --> 00:03:04,350
of type.

42
00:03:04,350 --> 00:03:06,300
String will be of type event.

43
00:03:06,840 --> 00:03:07,200
So.

44
00:03:08,560 --> 00:03:13,570
This is an event, and this year is a string.

45
00:03:14,260 --> 00:03:22,870
All right, it's are used for whole numbers and they require a certain amount of space in our memory.

46
00:03:24,230 --> 00:03:28,400
For example, an integer requires 32 bits of memory.

47
00:03:29,420 --> 00:03:32,870
If we want to use other types, they're available as well.

48
00:03:33,350 --> 00:03:36,440
So I'm just going to paste in some other types in here.

49
00:03:36,740 --> 00:03:44,190
For example, there is this type called byte, then this type called short, the type called end and

50
00:03:44,210 --> 00:03:45,410
type called long.

51
00:03:46,070 --> 00:03:52,190
And all of them are integer types and integer types are whole numbers.

52
00:03:52,700 --> 00:03:56,900
And each of them requires a different amount of space.

53
00:03:57,350 --> 00:04:05,420
So, for example, a byte is just eight bits, requires a bits in the memory, a short requires 16 bits

54
00:04:05,420 --> 00:04:09,890
in memory and 32 bits and long 64 bits.

55
00:04:10,760 --> 00:04:13,460
Now here it says the value is out of range.

56
00:04:13,550 --> 00:04:17,779
So this value is too long for even a long value.

57
00:04:18,200 --> 00:04:23,450
So if you have a very long number, this could be used, for example, for a Social Security number

58
00:04:23,450 --> 00:04:28,620
or for a credit card number, then you could use it long and here.

59
00:04:29,090 --> 00:04:31,430
Actually, it doesn't fit like this anymore.

60
00:04:31,580 --> 00:04:34,730
So I stood like that.

61
00:04:37,260 --> 00:04:39,090
And then we have a super long number here.

62
00:04:39,840 --> 00:04:44,940
Now you might wonder, why is this bytes dropped short and where are all of these coming from?

63
00:04:45,420 --> 00:04:47,970
Well, they come from me answering them.

64
00:04:48,150 --> 00:04:54,270
So here I explicitly say this variable called my byte should be of type byte.

65
00:04:54,630 --> 00:04:55,380
How do you do that?

66
00:04:55,500 --> 00:05:00,240
Well, I can do that by using the colon and afterwards to type.

67
00:05:01,230 --> 00:05:08,640
But of course, if I use a byte type, I can not use a long number because note will say.

68
00:05:09,670 --> 00:05:13,480
The integer literal does not conform to the expected Typekit.

69
00:05:14,050 --> 00:05:22,630
This means that the value that I entered here is so long that it's usually an integer, but we are trying

70
00:05:22,630 --> 00:05:27,910
to store it in a byte variable and that doesn't work because an integer needs a lot more space than

71
00:05:27,910 --> 00:05:28,360
a bite.

72
00:05:28,810 --> 00:05:33,940
So we need to make sure that the value that we assign here is correct.

73
00:05:34,480 --> 00:05:36,790
Now, at the same time, we don't need to do that.

74
00:05:37,090 --> 00:05:38,530
You see, I do that here.

75
00:05:38,620 --> 00:05:39,670
I say, this is a bar.

76
00:05:39,700 --> 00:05:40,690
This is a short isn't.

77
00:05:40,890 --> 00:05:43,210
This isn't long, but we don't need to do that.

78
00:05:43,210 --> 00:05:43,900
You saw it here.

79
00:05:44,230 --> 00:05:51,010
I just assigned a value 31 and that will automatically assign the right data type.

80
00:05:51,700 --> 00:05:56,890
And usually, if you don't explicitly say that you want to have a byte or short, it will just assign

81
00:05:57,610 --> 00:05:58,300
an integer.

82
00:05:58,750 --> 00:06:01,180
Cotton will just assume that this is an integer.

83
00:06:01,660 --> 00:06:02,380
How do you know that?

84
00:06:02,470 --> 00:06:07,930
Well, you can just enter my h, and you can see here on the right hand side that it is an integer.

85
00:06:08,170 --> 00:06:08,590
So.

86
00:06:09,790 --> 00:06:16,690
Scotland did the magic for us, and it automatically assigned to Typekit, which is called or does approach

87
00:06:16,690 --> 00:06:19,210
here is called type inference.

88
00:06:20,020 --> 00:06:24,640
So it just inferred to type based on whatever value we assign to it.

89
00:06:25,240 --> 00:06:28,540
Of course, if we do so, then we have to assign a value to it.

90
00:06:29,200 --> 00:06:33,220
So I cannot just create who are my age without assigning a value to it.

91
00:06:33,310 --> 00:06:35,470
I need to assign a value to it.

92
00:06:37,560 --> 00:06:39,690
There are a bunch of other types as well.

93
00:06:40,140 --> 00:06:42,810
So these are the integer types that we looked at.

94
00:06:43,170 --> 00:06:46,530
Now let's look at the floating point number types.

95
00:06:46,740 --> 00:06:50,610
So there are types which are required for floating point numbers.

96
00:06:50,880 --> 00:06:55,830
For example, the floating point number types float, which is a 32 bit.

97
00:06:57,200 --> 00:07:00,200
Data type and double, which is a 64 bit data type.

98
00:07:00,680 --> 00:07:06,650
Now here I'm assigning one three or thirteen point thirty seven to my flawed variable, which I called

99
00:07:06,650 --> 00:07:08,960
my flawed, but it's still complaining.

100
00:07:09,200 --> 00:07:10,310
So what's wrong here?

101
00:07:10,670 --> 00:07:17,360
Well, if I assign a floating point value, it usually assumes that I want to assign a double.

102
00:07:17,600 --> 00:07:26,030
As you can see here, but if I explicitly only want to use a float which has a lower range, so which

103
00:07:26,420 --> 00:07:28,550
just can't be as long as that of a number?

104
00:07:28,910 --> 00:07:34,160
Then I have to explicitly state that by adding an f at the end, this f stands for float.

105
00:07:34,430 --> 00:07:39,140
So I'm just saying, okay, this variable should be of type float or this value that I'm assigning here.

106
00:07:39,500 --> 00:07:47,180
So if I should get rid of this, for example, and I now check my float, you will see that it is a

107
00:07:47,180 --> 00:07:47,540
float.

108
00:07:48,380 --> 00:07:48,860
All right.

109
00:07:48,890 --> 00:07:54,140
So if I get rid of this f and I check what my float is, you can see now it's a double.

110
00:07:54,670 --> 00:08:01,730
And that has to do with me assigning this f to it and explicitly stating that it should be a float.

111
00:08:03,700 --> 00:08:07,330
So if you really need to save space, you can use floats.

112
00:08:07,540 --> 00:08:15,070
If the numbers are not going to be huge, but if you need flexibility, long numbers or you just don't

113
00:08:15,070 --> 00:08:16,960
care about space, then you can use doubles.

114
00:08:17,230 --> 00:08:22,960
And generally speaking, doubles are preferred by Scotland, or they will be most of the time use if

115
00:08:22,960 --> 00:08:25,480
you don't explicitly state that it's going to be a float.

116
00:08:26,950 --> 00:08:32,559
Using floats is important, for example, when you develop video games and you want to calculate the

117
00:08:32,559 --> 00:08:39,669
physics, then having as fast as possible calculations will be more important than having super duper

118
00:08:39,669 --> 00:08:40,270
precision.

119
00:08:40,630 --> 00:08:42,549
So that's where flood comes into play.

120
00:08:42,970 --> 00:08:45,790
But most of the time, stubble will be your way to go.

121
00:08:46,270 --> 00:08:46,570
All right.

122
00:08:46,570 --> 00:08:49,660
So these are the number types, but there are other types as well.