1
00:00:01,280 --> 00:00:05,910
And this lecture, I will explain every single word in the code we wrote in the previous video.

2
00:00:06,350 --> 00:00:09,470
So this code is to display may the force be with you.

3
00:00:09,830 --> 00:00:15,260
OK, so first we created a class, then we added the main method to it.

4
00:00:15,560 --> 00:00:19,640
And last we added a command that printed out this sentence.

5
00:00:20,120 --> 00:00:22,890
Now, let's start with some main parts of the code.

6
00:00:23,510 --> 00:00:27,230
First of all, keywords, Java has many keywords.

7
00:00:27,230 --> 00:00:31,260
And A.J., they are highlighted with the style of Scientology.

8
00:00:31,400 --> 00:00:32,410
They are orange.

9
00:00:32,900 --> 00:00:35,400
They must be used in a specific order.

10
00:00:35,720 --> 00:00:37,850
Also, they are case sensitive.

11
00:00:38,000 --> 00:00:44,090
So public with lower case doesn't equal to public, starting with an uppercase.

12
00:00:44,660 --> 00:00:47,080
OK, let's move from the top to the bottom.

13
00:00:47,540 --> 00:00:55,250
So public public is an access modifier, which defines how other parts of the code can use this code

14
00:00:55,250 --> 00:00:56,970
block besides public.

15
00:00:56,990 --> 00:01:02,600
There are other access modifiers to like private, protected and packaged private.

16
00:01:03,200 --> 00:01:04,500
But more on this later.

17
00:01:05,000 --> 00:01:07,130
The next keyword is Klasky word.

18
00:01:07,760 --> 00:01:10,280
It is just used to define a class.

19
00:01:11,190 --> 00:01:17,940
After that, the name of the class, which is the same as the name of the file after the class name

20
00:01:18,420 --> 00:01:26,130
Curly Braces, defines the scope, the area, the territory of the class or the code inside the curly

21
00:01:26,130 --> 00:01:28,270
braces belongs to the class.

22
00:01:28,710 --> 00:01:35,760
So just to summarize this, to define a class, you need to have an X modifier, which is optional then

23
00:01:35,910 --> 00:01:38,460
the class keyword, which is mandatory.

24
00:01:38,670 --> 00:01:42,180
And finally, the name of the class with the curly braces.

25
00:01:43,110 --> 00:01:45,020
Now let's move on to the main method.

26
00:01:45,120 --> 00:01:52,050
So what our methods methods are used to group together operations connected to each other.

27
00:01:52,770 --> 00:01:54,630
Methods also have a name.

28
00:01:54,930 --> 00:02:01,850
And by using that name, you can run the operations in the method from several different places.

29
00:02:02,340 --> 00:02:05,950
So it is a very good tool to make your code reusable.

30
00:02:06,720 --> 00:02:13,620
Also, they make your code more readable because the operations connected to each other grouped into

31
00:02:13,620 --> 00:02:20,400
one single unit in other programming languages, methods, maybe court procedures or functions.

32
00:02:21,180 --> 00:02:23,520
Now let's move on to the main method.

33
00:02:24,150 --> 00:02:25,650
It is a special method.

34
00:02:25,770 --> 00:02:28,700
It is a starting point for running Java programs.

35
00:02:28,980 --> 00:02:36,240
So when you run your Java code, it starts from the main method and runs and uses code that is written

36
00:02:36,240 --> 00:02:39,200
here and used to other classes.

37
00:02:39,840 --> 00:02:42,700
So let's go into some details public.

38
00:02:42,720 --> 00:02:44,340
As I said, it is an axis.

39
00:02:44,340 --> 00:02:51,810
Modifier static shows that this method belongs to the class rather than the object that you can create

40
00:02:51,810 --> 00:02:52,890
from this class.

41
00:02:53,520 --> 00:02:54,640
To understand this.

42
00:02:54,840 --> 00:02:59,910
First you need to know classes and objects and the difference between the two concepts.

43
00:03:00,210 --> 00:03:02,280
Don't worry, it is not rocket science.

44
00:03:02,590 --> 00:03:05,320
I will make it all clear later in the course.

45
00:03:06,030 --> 00:03:08,610
Now let's move on to the next keyword void.

46
00:03:09,210 --> 00:03:17,520
Void means that this main method doesn't return anything, a number or text or something else.

47
00:03:17,950 --> 00:03:19,710
It simply runs an action.

48
00:03:19,710 --> 00:03:22,740
Like here a text is printed out to the screen.

49
00:03:23,490 --> 00:03:31,380
OK, the next one is Main, which is the name of the function then to parentheses, which shows Java

50
00:03:31,710 --> 00:03:33,390
that it is a function.

51
00:03:33,750 --> 00:03:42,150
And in the parentheses there are parameters like here string square brackets, args string square brackets,

52
00:03:42,150 --> 00:03:48,230
which is an array, a list of text and ARGs is the name of that list.

53
00:03:48,720 --> 00:03:54,110
Here you can see how it would look like if we would store values in the args array.

54
00:03:54,780 --> 00:04:03,150
We use the name and then square brackets than a number in the square brackets to get the element of

55
00:04:03,150 --> 00:04:03,920
this array.

56
00:04:04,590 --> 00:04:11,430
We will look more into this later in the arrays lectures and lost the curly braces that belong to the

57
00:04:11,430 --> 00:04:15,110
main method which shows the scope of the main method.

58
00:04:15,300 --> 00:04:19,830
So every command between these curly braces belongs to the main method.

59
00:04:20,340 --> 00:04:26,250
OK, so the last part of this code is the system that ordered print online and the text.

60
00:04:26,790 --> 00:04:28,380
So what is system?

61
00:04:28,380 --> 00:04:30,180
What is out and what is print?

62
00:04:30,180 --> 00:04:36,380
Alarm system is an inbuilt class of Java and it represents your computer system.

63
00:04:36,810 --> 00:04:43,230
Then out is a field, an attribute in a system which is responsible for the outputs.

64
00:04:43,920 --> 00:04:52,110
For example, to show something on the screen and print plan or print line is a method or function of

65
00:04:52,110 --> 00:04:52,590
out.

66
00:04:53,310 --> 00:04:55,560
It prints out one single line.

67
00:04:56,160 --> 00:05:03,060
The parentheses show that this is a function and its parameter is the text we would like to print out

68
00:05:03,060 --> 00:05:04,560
between two double quotes.

69
00:05:05,100 --> 00:05:08,820
One last thing here is the semicolon at the end of the line.

70
00:05:09,150 --> 00:05:15,570
It is a must for every single command, but you don't have to use it at the definition of classes or

71
00:05:15,570 --> 00:05:16,230
methods.

72
00:05:16,680 --> 00:05:22,230
If you miss it, Java will warn you that the semicolon is missing from the end of the line.

73
00:05:22,570 --> 00:05:23,880
Let's give it a try now.

74
00:05:23,880 --> 00:05:28,260
I'm going to delete this semicolon here and let's run the code.

75
00:05:32,660 --> 00:05:38,270
And as you can see, a semicolon is missing from the end of the line, and Java expected a semicolon

76
00:05:38,270 --> 00:05:38,600
there.

77
00:05:38,940 --> 00:05:46,550
If you click somewhere else and you click on this error message here, the cursor will jump right to

78
00:05:46,550 --> 00:05:49,010
the place where the semicolon should be.

79
00:05:49,760 --> 00:05:54,440
And if I add a semicolon again and I run the code again.

80
00:05:58,890 --> 00:06:06,690
You can see it is running again and we got zero exit code, so what I suggest you to do here is to print

81
00:06:06,690 --> 00:06:13,680
out something else and also change the order of the key words just to explore what air or message you

82
00:06:13,680 --> 00:06:14,310
can get.

83
00:06:14,520 --> 00:06:16,720
Don't worry, you cannot do any harm.

84
00:06:16,740 --> 00:06:17,700
It is just code.

85
00:06:18,000 --> 00:06:23,310
You can always find the code of the lecture next to the lectures title as a resource.

86
00:06:24,150 --> 00:06:24,890
All right.

87
00:06:24,900 --> 00:06:25,510
That's it.

88
00:06:25,680 --> 00:06:27,090
See you in the next lecture.