1

00:00:00,140 --> 00:00:06,330

So at the first instance variable is going to be of type string and the name of this instance variable



2

00:00:06,420 --> 00:00:12,530

is computer computer name semicolon.



3

00:00:12,860 --> 00:00:15,310

And then let me show you the emulator here.



4

00:00:15,560 --> 00:00:18,530

So the first one is computer name as you can see here.



5

00:00:18,800 --> 00:00:23,500

And then we need to actually create another instance variable which is for computer power.



6

00:00:23,540 --> 00:00:31,210

So this instance variable is going to be our third integer computer power semicolon.



7

00:00:31,850 --> 00:00:34,080

And here we have computer speed.



8

00:00:34,100 --> 00:00:41,810

So here I can say ain't computer speed semicolon.



9

00:00:42,350 --> 00:00:46,600

And make sure to also declare them and declare them as private.



10

00:00:46,730 --> 00:00:50,780

So use this private access modifier for this instance variables.



11

00:00:51,290 --> 00:00:59,390

So private stream computer name private int a computer power private in a computer speed and an instance



12

00:00:59,390 --> 00:01:01,980

variable is for this one computer run.



13

00:01:02,060 --> 00:01:09,830

So here I can say private in computer ram semi-colon.



14

00:01:10,220 --> 00:01:12,870

And the next one is computer screen.



15

00:01:12,920 --> 00:01:14,990

So private



16

00:01:19,080 --> 00:01:25,270

strange computer screen semi-colon.



17

00:01:25,680 --> 00:01:28,040

The next one is keyboard computer keyboard.



18

00:01:28,050 --> 00:01:40,760

So private strange computer keyboard semicolon and the next one is computer CPQ.



19

00:01:40,980 --> 00:01:51,390

So here I can say again private strange computer CPQ semicolon.



20

00:01:51,750 --> 00:01:54,260

So now we have this instance variables.



21

00:01:54,330 --> 00:01:59,270

So let's actually create an empty constructor for this class because we need it.



22

00:01:59,340 --> 00:02:06,090

If you want to actually use it inside of an activity class because of you want to store our values to



23

00:02:06,090 --> 00:02:12,120

these instance variables and we want to actually just send these values to the firebase.



24

00:02:12,130 --> 00:02:16,390

So let's actually create an empty constructor so public.



25

00:02:16,890 --> 00:02:20,660

And again the name of the constructor must be the same as the name of the class.



26

00:02:20,910 --> 00:02:22,600

Public computer.



27

00:02:22,980 --> 00:02:27,820

And then here I just need to put up a pair of Prentice's here.



28

00:02:28,000 --> 00:02:29,830

I should be an empty parenthesis.



29

00:02:30,000 --> 00:02:33,600

And then I need to open and close this constructed by using these curly braces.



30

00:02:33,600 --> 00:02:35,760

So this is going to be an empty constructor.



31

00:02:35,790 --> 00:02:36,350

Right.



32

00:02:36,750 --> 00:02:44,250

And now let's actually create another constructor so that we can actually initialize our instance variables



33

00:02:44,250 --> 00:02:45,760

inside our constructor.



34

00:02:45,780 --> 00:02:53,430

So here inside this class inside this computer class just right click here and then click on generate



35

00:02:54,330 --> 00:03:01,890

and then click on constructor and here select all these instance variables just press the shift key



36

00:03:01,890 --> 00:03:08,470

on your keyboard and just select all these instance variables and then click on OK.



37

00:03:08,640 --> 00:03:15,180

So now as you can see we have actually a constructor here that is created automatically by yantra studio



38

00:03:15,180 --> 00:03:15,990

for us.



39

00:03:15,990 --> 00:03:21,210

So let me actually create a newline character here so that you can see these values here.



40

00:03:21,240 --> 00:03:25,920

So we have actually a constructor and this construction accepts some arguments.



41

00:03:25,920 --> 00:03:28,580

The first one is computer name which is of type string.



42

00:03:28,830 --> 00:03:32,760

The second argument is actually of the integer and is computer power.



43

00:03:32,760 --> 00:03:36,680

The first argument is computer speed which is an integer.



44

00:03:36,990 --> 00:03:43,720

And we have this computer RAM which is of type integer computer screen screen and computer keyboards



45

00:03:43,810 --> 00:03:44,170

training.



46

00:03:44,190 --> 00:03:47,560

And finally we have this computer Sibiu which is of type string.



47

00:03:47,730 --> 00:03:52,370

And inside the curly braces of this constructed as you can see here we are actually initialising which



48

00:03:52,650 --> 00:03:54,180

are instance variables.



49

00:03:54,270 --> 00:03:58,500

So this computer name refers to this computer name here right.



50

00:03:58,500 --> 00:04:03,920

Assignment operator computer name this computer power assignment operator computer power.



51

00:04:04,230 --> 00:04:08,790

And here T-stat computer speed assignment operator computer speed.



52

00:04:08,790 --> 00:04:15,310

So he had this current data computer the refers to these computers here that we have and this that computer



53

00:04:15,310 --> 00:04:18,480

ram time assignment operator computer ram as you can see here.



54

00:04:18,480 --> 00:04:25,020

This computer screen assignment operator computer screen this that computer keyboard assignment operator



55

00:04:25,020 --> 00:04:26,970

computer keyboard as you can see.



56

00:04:26,970 --> 00:04:30,590

And these computers Sibiu you assignment operator computer spew.



57

00:04:30,900 --> 00:04:38,430

So here this keyword actually refers to an instance that we are going to create from this computer class.



58

00:04:38,460 --> 00:04:38,750

Right.



59

00:04:38,760 --> 00:04:46,040

When I say these computer name refers to an instance of this class that actually has this computer in



60

00:04:46,040 --> 00:04:47,320

an instance variable.



61

00:04:47,400 --> 00:04:50,570

So that's why it is called instance variable right.



62

00:04:50,580 --> 00:04:57,060

So this computer name is actually adding to the instance variable assignment operator computer name



63

00:04:57,210 --> 00:04:59,320

refers to this argument.



64

00:04:59,400 --> 00:05:00,370

Right.



65

00:05:00,390 --> 00:05:02,470

So hopefully that makes sense.



66

00:05:02,530 --> 00:05:09,630

And now this actually creates the getters and they get this that we need for these instance variables.



67

00:05:09,630 --> 00:05:17,340

So again before the end in calibrates of this class and inside this class just right click here and



68

00:05:17,340 --> 00:05:21,580

then we can generate and he can get it right.



69

00:05:21,750 --> 00:05:24,810

And he had against select all these instance variables.



70

00:05:24,810 --> 00:05:30,390

So just hold the shift key on your keyboard and select all these instance variables and then click on



71

00:05:30,420 --> 00:05:31,070

OK.



72

00:05:31,370 --> 00:05:36,690

So now as you can see here all these getters are actually the generators for us automatically by the



73

00:05:36,690 --> 00:05:37,860

Android studio.



74

00:05:37,920 --> 00:05:38,550

Right.



75

00:05:38,550 --> 00:05:42,550

So we have actually get help for the computer name public screen.



76

00:05:42,780 --> 00:05:45,370

Gates can actually see you.



77

00:05:45,600 --> 00:05:50,480

So as you can see here the order is not actually important here.



78

00:05:50,610 --> 00:05:53,240

So the first Gittel is for the computer Sibiu.



79

00:05:53,310 --> 00:06:00,360

So publics can get computers is actually a method that is going to return the value of the compute computer



80

00:06:00,390 --> 00:06:02,250

Sibiu instance variable.



81

00:06:02,640 --> 00:06:07,980

And here we have public street get a computer name that is going to return the value of the computer



82

00:06:07,980 --> 00:06:12,410

name public end gets computer power.



83

00:06:12,420 --> 00:06:19,080

As you can see here returned computer power public integrates computer speed written computer speed



84

00:06:19,410 --> 00:06:27,300

public interface computer ram written computer ram public street kids computer screen right hand computer



85

00:06:27,300 --> 00:06:27,820

screen.



86

00:06:27,930 --> 00:06:34,070

And finally we have this method public is three jet's computer keyboard written computer keyboard.



87

00:06:34,140 --> 00:06:36,510

So this is our computer class right.



88

00:06:36,510 --> 00:06:44,190

So let's go back to our main activity the job right here and now let's actually just declare some objects



89

00:06:44,190 --> 00:06:44,510

here.



90

00:06:44,520 --> 00:06:50,790

The first object that we need to declare here is actually firebase database and the name of our Optik



91

00:06:50,790 --> 00:06:53,410

is going to be firebase database semi-colon.



92

00:06:53,700 --> 00:06:59,430

And the second object is of type database reference and the name of this object is database reference.



93

00:06:59,430 --> 00:07:00,110

Right.



94

00:07:00,300 --> 00:07:06,690

So this Firebrace database here is going to actually help us to actually get the firebase instance.



95

00:07:06,690 --> 00:07:09,030

So let me show you the other browser.



96

00:07:09,030 --> 00:07:15,770

So as you can see here this is our web browser and this is actually a database instance right.



97

00:07:15,810 --> 00:07:22,230

So now as you can see here we have this instance and we have this database reference that can actually



98

00:07:22,230 --> 00:07:24,250

help us to find the reference.



99

00:07:24,330 --> 00:07:32,190

And actually we can actually work on our references and we can add references and work on our database.



100

00:07:32,310 --> 00:07:34,410

So let's go back to our Android studio.



101

00:07:34,410 --> 00:07:36,940

So the first object is firebase database.



102

00:07:37,110 --> 00:07:39,500

And the second object is database reference.



103

00:07:39,540 --> 00:07:44,730

So here inside is uncreate Mefford Let's actually initialize these objects that we declared here in



104

00:07:44,730 --> 00:07:46,890

line number 28 and 29.



105

00:07:47,190 --> 00:07:49,280

So the first object is firebase database.



106

00:07:49,350 --> 00:07:54,510

Inside this uncreate my feet I can say firebase database assignment operator.



107

00:07:54,720 --> 00:07:59,310

And here I can say firebase database that gets instance semicolon.



108

00:07:59,850 --> 00:08:05,520

In fact let's actually change the name of this variable which is of type firebase database.



109

00:08:05,520 --> 00:08:10,640

So here inside this class as you can see in line number 28 we actually created this value right.



110

00:08:10,650 --> 00:08:12,170

We declared this variable.



111

00:08:12,540 --> 00:08:14,810

And we named it firebase database.



112

00:08:14,820 --> 00:08:19,330

So let's actually just name it firebase database instance right.



113

00:08:19,410 --> 00:08:24,090

It's more meaningful firebase database instance and inside is uncreate unfaith.



114

00:08:24,260 --> 00:08:27,680

There's actually just type in firebase database instance.



115

00:08:27,690 --> 00:08:33,930

So now I have to firebase database instance right by calling this method we get the firebase database



116

00:08:33,930 --> 00:08:34,620

instance.



117

00:08:34,890 --> 00:08:41,580

And now let's say actually initialize this database reference here.



118

00:08:41,580 --> 00:08:47,390

So now here after this line of code I can't say databased or France assignment operator.



119

00:08:47,520 --> 00:08:53,220

And then I need to refer to the name of this instance firebase database instance so Firebrace database



120

00:08:53,280 --> 00:08:57,780

instance it get the reference as you can see here.



121

00:08:57,870 --> 00:09:00,890

Choose this one with this argument which is of type string.



122

00:09:01,260 --> 00:09:04,120

And now I need to provide an argument of types 3.



123

00:09:04,150 --> 00:09:11,470

So inside Apprentice's just put two double quotes and you want to get to instance to computers category.



124

00:09:11,850 --> 00:09:16,620

So here all you want to actually create reference to our computer.



125

00:09:16,620 --> 00:09:19,290

The computers category so I want to create.



126

00:09:19,290 --> 00:09:20,120

So let's go back.



127

00:09:20,220 --> 00:09:22,120

Let's go to our web browser here.



128

00:09:22,140 --> 00:09:29,220

So as you can see here when I say unable to actually just create a category here I can just click on



129

00:09:29,220 --> 00:09:36,870

this child here and here I can say for example computers light computers and because I want to create



130

00:09:36,870 --> 00:09:41,430

a category we do not actually provide a value for this value here.



131

00:09:41,430 --> 00:09:42,060

Right.



132

00:09:42,090 --> 00:09:48,810

So we just again click on these I tried here and now as you can see these computers is actually a category



133

00:09:48,810 --> 00:09:51,420

that can contain other types.



134

00:09:51,480 --> 00:09:52,160

Right.



135

00:09:52,170 --> 00:09:54,880

So that's what you want to do with the code.



136

00:09:54,960 --> 00:09:59,970

So let's go back to what Android studio when I actually just referred to this database reference here



137

00:10:00,450 --> 00:10:03,300

I am actually just referring to this instance.



138

00:10:03,300 --> 00:10:03,730

Right.



139

00:10:03,780 --> 00:10:10,070

So this instance firebase database instance is has the inside has the database instance right.



140

00:10:10,180 --> 00:10:15,400

These firebase database instance already has the database instance.



141

00:10:15,630 --> 00:10:18,040

So what do I mean by database instance.



142

00:10:18,090 --> 00:10:22,550

This means that we already have access to this instance.



143

00:10:22,680 --> 00:10:23,610

As you can see here.



144

00:10:23,910 --> 00:10:30,050

But now because I want to actually create a category by using Java codes as you can see here in line



145

00:10:30,060 --> 00:10:38,580

number 58 I just referred to the name of this database reference so that we can actually just hold the



146

00:10:38,580 --> 00:10:44,940

database reference inside this variable and then I put an assignment operator here and then I'll refer



147

00:10:45,000 --> 00:10:52,050

to the name of this firebase database instance and then I want to actually create a reference to our



148

00:10:52,050 --> 00:10:56,970

category and then after this we can actually add children to this category.



149

00:10:57,120 --> 00:11:00,500

So firebase database instance that reference computers.



150

00:11:00,540 --> 00:11:05,890

So this line of code here is like this one here as you can see we created a category computer.



151

00:11:06,060 --> 00:11:12,570

And now this database defense has a reference to the computers category inside our database.



152

00:11:12,570 --> 00:11:14,480

Not this one but this one.



153

00:11:14,640 --> 00:11:17,040

So let's you delete this one here.



154

00:11:17,070 --> 00:11:19,170

Let's go back to our Android studio and what.



155

00:11:19,180 --> 00:11:21,390

Now I want to show you that how this works.



156

00:11:21,390 --> 00:11:25,960

So here for example I can say database reference dots tied.



157

00:11:26,220 --> 00:11:34,350

And now I can actually provide the child so the child could be for example key and he or dot set value



158

00:11:34,620 --> 00:11:39,420

and the value could be for example value added with a semicolon at the end of my statement.



159

00:11:39,420 --> 00:11:39,930

Right.



160

00:11:40,020 --> 00:11:46,440

So now let's run our project and now let me show you the web browser and the emulator



161

00:11:48,960 --> 00:11:54,140

so as you can see here now we have these computers category as you can see here.



162

00:11:54,420 --> 00:12:00,390

And inside these computers tactically we have these key and value so that that's how you can actually



163

00:12:00,390 --> 00:12:05,310

create a category by using your double quotes by you writing double quotes.



164

00:12:05,310 --> 00:12:08,340

You can also create categories and children here.



165

00:12:08,640 --> 00:12:09,750

So that's how you do it.



166

00:12:09,810 --> 00:12:15,330

So now in line number six the list actually deletes this line of code here and now you know that we



167

00:12:15,420 --> 00:12:18,780

have actually our reference to these computers category.



168

00:12:18,780 --> 00:12:25,500

So if I had on my project nothing happens let's actually go back to our Web browser and see if we actually



169

00:12:25,500 --> 00:12:29,530

did it this instance here this category.



170

00:12:29,640 --> 00:12:34,230

As you can see here now that I am actually running this project as as you can see here nothing happens.



171

00:12:34,230 --> 00:12:34,880

Why.



172

00:12:34,890 --> 00:12:39,820

Because it in line number 58 inside and inside our Android studio.



173

00:12:39,880 --> 00:12:46,230

You're saying that we are going to have a category that is actually computers but but because we haven't



174

00:12:46,230 --> 00:12:50,810

still provided tights for this category the database is not going to show us.



175

00:12:50,880 --> 00:12:55,400

So that for us because this chatter doesn't have children.



176

00:12:55,410 --> 00:13:01,680

So first we need to provide the children and then we can see these computers category inside our database.



177

00:13:01,800 --> 00:13:02,450

As you can see here.



178

00:13:02,460 --> 00:13:05,750

But for now nothing just happens here.



179

00:13:05,820 --> 00:13:07,380

So let's go back to what I understood you.



180

00:13:07,470 --> 00:13:12,820

So now you know that this database of friends has a reference to the computers category.



181

00:13:12,840 --> 00:13:13,950

So now.