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| (piano music) |
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| 2 |
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| -: Now once we have our setup done, it's time |
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| to write our first code. |
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| 4 |
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| That's right. |
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| 5 |
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| So finally we are going |
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| to run our first Java code here. |
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| Now for that we have to open our editor. |
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| So of course in the last video we have discussed |
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| that we are going to use VS code. |
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| So let's open VS code here. |
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| 11 |
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| So I will say code. |
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| 12 |
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| Okay, so our VS code is all set to write our first code. |
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| 13 |
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| You can see it, it will give you a welcome screen |
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| 14 |
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| when you do it and then it will ask the preference, |
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| do you want a light color, dark color, dark, high contrast |
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| or light high contrast. |
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| I would say go for dark because it's good for development. |
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| It will not strain your eyes at least. |
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| So let's close this. |
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| Get started and this is how your VS code will look like. |
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| 21 |
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| Okay, simple stuff. |
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| 22 |
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| Right now what we'll do is first of all |
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| where you will get your folder. |
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| So you will see your folders on the left hand side. |
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| So this is where you will get your project, |
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| all the files which you want to work with. |
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| So you'll be having that here. |
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| 28 |
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| Now of course in the upcoming tutorials, |
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| we'll be using a different IDE |
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| and I want you to get used |
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| to different IDs when you work with. |
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| So on the left hand side we can see we have an explorer here |
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| and then we, if you want |
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| to search something, we have it here. |
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| If you want to add some extensions, which we are going |
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| to do later, we will add certain extensions to work with. |
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| At this point, we don't need any extension, |
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| so just keep it blank. |
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| 39 |
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| I mean, no need, no need to install anything here. |
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| In my machine I already have something |
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| on some other accounts, |
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| but on this account I don't think so. |
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| Anyway. |
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| 44 |
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| And then if you want to run |
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| and debug it, you debug, you will find the option here. |
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| Now why do we run of, of course we know what |
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| to, why to run, right? |
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| 48 |
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| But why do we debug the application? |
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| 49 |
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| Yeah, we'll see that later. |
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| 50 |
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| At this point, |
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| 51 |
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| let's open our files of explorer here. |
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| 52 |
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| And this is where I want to create my first project. |
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| 53 |
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| Now, how do we create a project? |
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| 54 |
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| Now project will be a very broad term at this point. |
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| What we are going to do is we will create some files |
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| and of course when you merge these files |
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| and libraries, you create a project. |
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| At this point we do, we are not working |
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| with any external libraries. |
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| At this point, |
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| we are just going for a simple files, okay? |
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| Hello world, right? |
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| So for that |
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| what we'll do is we'll click on open folder |
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| because all these files will be part |
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| of one particular folder. |
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| So we'll click on Open Folder |
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| and it'll give you certain options |
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| where you want to save this. |
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| So I will save this in my desktop itself. |
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| In fact, on my desktop I want to create one more folder. |
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| So I will say open folder again, inside desktop I will, |
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| I want to create a folder here. |
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| We'll say, this is, I will have a short name, |
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| we'll say, Course, Create and Open. |
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| So you can see we got our course folder here. |
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| What I will do is I will zoom in in inside my VS code so |
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| that you can see everything properly. |
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| 79 |
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| And again, the recommendation would be |
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| to watch this on a bigger screen so |
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| that you know you can actually |
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| 82 |
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| understand each and every line. |
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| 83 |
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| Because in mobile, sometime you will be seeing a font size |
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| and a small font. |
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| I don't want to see this page every time I open my VS codes, |
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| so I will just uncheck this and click on close here |
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| 87 |
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| and let's create our first file. |
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| 88 |
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| And this is where you are going |
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| to write our first code, right? |
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| 90 |
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| So we have already seen how do we install JDK, how do we |
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| check the version on the terminal? |
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| 92 |
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| Can you do that in this? |
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| 93 |
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| So VS code itself has a terminal here, so you don't have |
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| to open the external terminal. |
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| 95 |
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| Of course if you're using Windows, |
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| 96 |
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| you'll be having an option of command prompt. |
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| 97 |
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| But let's click on terminal here |
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| and you can see we have an option |
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| of terminal, click on this one. |
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| This is where you can enter your commands. |
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| Whatever commands you have. |
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| The same command we'll write here. |
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| 103 |
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| So we'll say Java version |
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| 104 |
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| and you can see I have Java 17 in this machine |
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| and Java 18 is already released. |
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| 106 |
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| But then Java 17 is the LTS version. |
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| 107 |
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| So when you say LTS, it means long-term support, right? |
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| 108 |
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| So we'll use that and we'll also check if my |
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| Java C is working. |
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| You can see Java C is also there. |
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| 111 |
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| Now Java C basically stands |
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| for Java compile as we discussed before. |
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| 113 |
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| So we need both. |
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| We need Java to run the application, we need Java C |
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| to compile the code, right? |
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| 116 |
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| Okay, cool. |
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| 117 |
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| So we got the number as well, |
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| 118 |
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| I will just minimize this a bit. |
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| 119 |
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| Okay, so now let's create our first file. |
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| 120 |
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| So what we are going to do is we'll click on this particular |
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| file here and we'll name this as hello.java. |
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| 122 |
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| Now there is something you have to remember, |
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| 123 |
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| whenever you create a Java project, you have to make sure |
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| that you give an extension or Java files. |
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| 125 |
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| Basically you have to give an extension with dot Java. |
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| 126 |
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| Now different languages have different extension. |
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| 127 |
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| When you talk about C, we say dot C, |
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| 128 |
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| when you say C plus plus language, we say dot CPP. |
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| 129 |
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| When you say Java script, we use dot JS. |
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| 130 |
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| In the same way, |
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| 131 |
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| in Java we say.java, simple stuff, right? |
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| 132 |
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| So you've got our file here. |
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| 133 |
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| Now VS code will give you some suggestions. |
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| 134 |
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| We'll ask you to install some extensions for Java |
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| 135 |
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| and we'll click on recommendation. |
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| 136 |
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| Okay, it is asking us extension pack for Java, |
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| 137 |
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| which will help us, |
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| 138 |
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| it will give you some options and extra stuff. |
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| 139 |
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| Again, this is just an advantage which you get from VS |
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| 140 |
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| code, again, not required. |
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| 141 |
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| If you don't want to install this extension, |
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| 142 |
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| I think I should go for it. |
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| 143 |
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| We also have intelli code for AI assistance. |
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| 144 |
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| But yeah, we'll stick to this extension. |
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| 145 |
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| Again, in your machine, you don't have |
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| 146 |
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| to install this, there's no compulsion. |
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| 147 |
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| You can still write your Java code, |
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| 148 |
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| but maybe it will give you some |
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| 149 |
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| suggestions and stuff in between. |
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| 150 |
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| Let's see, let's close this and let's write our code. |
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| 151 |
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| So extension will be installing behind the scene. |
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| 152 |
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| You don't have to worry about it. |
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| 153 |
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| So basically how do we write our Java code? |
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| 154 |
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| It's very simple actually. |
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| 155 |
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| First of all, the question is |
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| 156 |
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| what do you wanna do in this code? |
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| 157 |
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| Do you want to create a game |
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| 158 |
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| or do you want to build a rocket which will go to mass? |
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| 159 |
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| I'll not be doing those extra stuff. |
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| 160 |
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| What I will do now is I will create a very simple file which |
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| 161 |
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| will print hello world. |
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| 162 |
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| I know, that's how you start a programming language, right? |
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| 163 |
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| It is irrespective of which language you're learning, |
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| 164 |
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| the first thing you do is you print hello world. |
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| 165 |
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| So here I want to print hello world. |
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| 166 |
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| Now how do we do that? |
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| 167 |
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| See if you, in case if you are coming from other languages, |
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| 168 |
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| let's say Python, right? |
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| 169 |
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| So what you do is if you want |
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| 170 |
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| to print hello world in Python, you can write only one line |
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| 171 |
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| and maybe Java is not that famous |
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| 172 |
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| for simplicity at the start. |
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| 173 |
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| Of course when you build a bigger project, |
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| 174 |
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| Java is much more structured compared to the languages. |
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| 175 |
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| But then to start with, it's not that easy. |
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| 176 |
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| So just bear with me. |
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| 177 |
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| So what we are gonna do now is |
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| 178 |
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| if you want to just experiment |
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| 179 |
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| with Java, if you want to play some, if you want |
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| 180 |
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| to test some code or stuff, |
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| 181 |
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| we have an option which was introduced in Java nine. |
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| 182 |
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| So basically you can write your code, in one line |
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| 183 |
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| you can get the output example. |
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| 184 |
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| So even before we jump to hello |
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| 185 |
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| world, let me show you something. |
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| 186 |
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| So we have a op, we have a concept of J shell in Java. |
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| 187 |
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| So it was introduced in Java nine as I mentioned. |
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| 188 |
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| So you can open your terminal |
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| 189 |
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| and here let me just increase the size a bit. |
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| 190 |
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| So what I will do is I will click on J shell |
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| 191 |
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| or I will type J shell and it will give you a |
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| 192 |
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| J shell prompt. |
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| 193 |
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| Now J in this case is Java. |
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| 194 |
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| So you can it make, it should make sense now, okay? |
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| 195 |
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| So what you can do in Jshell is if you want |
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| 196 |
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| to experiment something, example, why do we write code? |
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| 197 |
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| Why do we build application? |
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| 198 |
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| So to solve problems right, now it can be a |
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| 199 |
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| very simple problem as well. |
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| 200 |
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| Example, if you want to add two numbers, it's very simple. |
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| 201 |
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| You can say two plus three. |
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| 202 |
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| And if I say enter, you can say we got five, right? |
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| 203 |
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| So we got the answer which is five, what if you want |
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| 204 |
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| to do a subtraction, you can do that. |
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| 205 |
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| So nine minus six, and you can see we got three. |
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| 206 |
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| So this is working, but what if you want to print something? |
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| 207 |
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| So in this case what you can do is when you were in Java, |
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| 208 |
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| if you want to do something, |
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| 209 |
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| we use something called methods. |
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| 210 |
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| At this point, you don't have to remember methods on |
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| 211 |
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| what the definition is. |
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| 212 |
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| Just remember that there's a concept called methods |
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| 213 |
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| using which you can do something. |
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| 214 |
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| The only thing you have to remember is if you want |
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| 215 |
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| to do something, you need methods. |
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| 216 |
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| In the same way, if you want to do something here, |
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| 217 |
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| I want to print something, right? |
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| 218 |
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| So we have to use a method called print. |
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| 219 |
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| It is a inbuilt method in Java so you don't have |
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| 220 |
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| to worry about it, just use it, it will work. |
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| 221 |
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| So whenever you call methods, you have to parse the values. |
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| 222 |
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| So I want to say, hey print, |
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| 223 |
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| but then it will say okay, I will print, |
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| 224 |
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| but what you want me to print? |
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| 225 |
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| So you can mention that in this bracket. |
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| 226 |
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| So in this round brackets, you can mention I want |
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| 227 |
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| to print hello world. |
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| 228 |
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| Now if you want to just print a number, |
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| 229 |
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| let's start with that first. |
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| 230 |
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| So let me just print a number, which is six. |
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| 231 |
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| And in Java there's one more thing. |
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| 232 |
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| You have to put a semicolon at the |
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| 233 |
| 00:07:47,000 |
| end, it should work in this. |
|
|
| 234 |
| 00:07:48,000 |
| But then living with this, at the end put a semicolon. |
|
|
| 235 |
| 00:07:51,000 |
| That's how you mentioned, hey, something is getting ended. |
|
|
| 236 |
| 00:07:54,000 |
| So we've got a semicolon there. |
|
|
| 237 |
| 00:07:55,000 |
| And now what you can do is let's try to run this code. |
|
|
| 238 |
| 00:08:00,000 |
| Now errors, right? |
|
|
| 239 |
| 00:08:01,000 |
| Error are very important in your life, |
|
|
| 240 |
| 00:08:02,000 |
| in your programming life, |
|
|
| 241 |
| 00:08:03,000 |
| basically you see you got the error. |
|
|
| 242 |
| 00:08:04,000 |
| It says cannot find a simple call print, it's not working. |
|
|
| 243 |
| 00:08:08,000 |
| Okay, cool, no problem. |
|
|
| 244 |
| 00:08:09,000 |
| So let me just clear the screen. |
|
|
| 245 |
| 00:08:11,000 |
| A clear comment is not working, ignore that. |
|
|
| 246 |
| 00:08:13,000 |
| So let me open Jshell once again and let's, |
|
|
| 247 |
| 00:08:15,000 |
| because I just want to keep it on top. |
|
|
| 248 |
| 00:08:17,000 |
| So what I will do now is if I want to print something |
|
|
| 249 |
| 00:08:19,000 |
| and I want to print a value six at the end, |
|
|
| 250 |
| 00:08:23,000 |
| I want a semi colon as well. |
|
|
| 251 |
| 00:08:25,000 |
| Now Java says if you want to call print, |
|
|
| 252 |
| 00:08:27,000 |
| print belongs to something, right? |
|
|
| 253 |
| 00:08:29,000 |
| So it it when I say it is available inside Java. |
|
|
| 254 |
| 00:08:31,000 |
| So the statement you have |
|
|
| 255 |
| 00:08:33,000 |
| to always mention is system.out.print again. |
|
|
| 256 |
| 00:08:36,000 |
| See there will be a point where you, I will, will talk about |
|
|
| 257 |
| 00:08:38,000 |
| what is system, what is out. |
|
|
| 258 |
| 00:08:40,000 |
| At this point it's very difficult to understand. |
|
|
| 259 |
| 00:08:41,000 |
| So just bear with me. |
|
|
| 260 |
| 00:08:43,000 |
| This is a statement which you have |
|
|
| 261 |
| 00:08:45,000 |
| to use if you want to print something on the console. |
|
|
| 262 |
| 00:08:49,000 |
| So if I want to print something here, |
|
|
| 263 |
| 00:08:51,000 |
| just say system.out.print |
|
|
| 264 |
| 00:08:53,000 |
| and whatever value you want to pass, say enter. |
|
|
| 265 |
| 00:08:56,000 |
| You can say we got six, |
|
|
| 266 |
| 00:08:57,000 |
| but what if you want to print hello world, |
|
|
| 267 |
| 00:08:59,000 |
| I don't want to print six. |
|
|
| 268 |
| 00:09:01,000 |
| So if you want to repeat the same statement, |
|
|
| 269 |
| 00:09:03,000 |
| of course you can type or you can click on the up arrow, |
|
|
| 270 |
| 00:09:06,000 |
| it will give you the option. |
|
|
| 271 |
| 00:09:07,000 |
| Now here if you want to print hello world, you have to put |
|
|
| 272 |
| 00:09:09,000 |
| that in double codes. |
|
|
| 273 |
| 00:09:10,000 |
| So whenever you want to do something with text, |
|
|
| 274 |
| 00:09:13,000 |
| see numbers are easy to use, you can simply say six. |
|
|
| 275 |
| 00:09:16,000 |
| But if you want to work with a text, you have to put |
|
|
| 276 |
| 00:09:19,000 |
| that in double codes the way I've done it here. |
|
|
| 277 |
| 00:09:21,000 |
| So in this double codes you have |
|
|
| 278 |
| 00:09:22,000 |
| to mention hello world, right? |
|
|
| 279 |
| 00:09:24,000 |
| That's how you start a programming, |
|
|
| 280 |
| 00:09:26,000 |
| programming journey, right? |
|
|
| 281 |
| 00:09:27,000 |
| I will say enter and you can say we got hello world, |
|
|
| 282 |
| 00:09:29,000 |
| what if I want to print something |
|
|
| 283 |
| 00:09:30,000 |
| else, which is very simple. |
|
|
| 284 |
| 00:09:32,000 |
| You can say double codes, not being ready, Telusko. |
|
|
| 285 |
| 00:09:35,000 |
| And if I say enter, you can say we got the text. |
|
|
| 286 |
| 00:09:37,000 |
| So whatever you want to print, just put that in double codes |
|
|
| 287 |
| 00:09:40,000 |
| and it should work. |
|
|
| 288 |
| 00:09:41,000 |
| And you can see we are getting the output as well, so cool. |
|
|
| 289 |
| 00:09:44,000 |
| So we are able to do this with the help of J shell, |
|
|
| 290 |
| 00:09:47,000 |
| but will it work in this? |
|
|
| 291 |
| 00:09:49,000 |
| If I try to copy this, in fact why |
|
|
| 292 |
| 00:09:51,000 |
| to copy it, we can type it. |
|
|
| 293 |
| 00:09:53,000 |
| So let's type system.out.print.ln, |
|
|
| 294 |
| 00:09:57,000 |
| and here we'll say hello world |
|
|
| 295 |
| 00:10:00,000 |
| and let's give a semi colon |
|
|
| 296 |
| 00:10:01,000 |
| at the end, it was working on J shell. |
|
|
| 297 |
| 00:10:04,000 |
| But when you work with Java files, |
|
|
| 298 |
| 00:10:06,000 |
| because this is how you build a project, right? |
|
|
| 299 |
| 00:10:07,000 |
| J shell is not to build projects, |
|
|
| 300 |
| 00:10:09,000 |
| it's just for the experiment. |
|
|
| 301 |
| 00:10:10,000 |
| If you are learning a language, it is good, |
|
|
| 302 |
| 00:10:12,000 |
| but if you want to build a big application, |
|
|
| 303 |
| 00:10:15,000 |
| say dot java file and write your code there. |
|
|
| 304 |
| 00:10:16,000 |
| So let's compile this code. |
|
|
| 305 |
| 00:10:17,000 |
| Now how do we compile? |
|
|
| 306 |
| 00:10:18,000 |
| Okay, so there, there are two steps you have to follow. |
|
|
| 307 |
| 00:10:20,000 |
| First, when you write a code, you have to compile the code |
|
|
| 308 |
| 00:10:23,000 |
| and then you can run the code. |
|
|
| 309 |
| 00:10:24,000 |
| So to compile the code, you can say Java C in the terminal, |
|
|
| 310 |
| 00:10:27,000 |
| and let me just increase the font a bit. |
|
|
| 311 |
| 00:10:29,000 |
| So you have to say Java C |
|
|
| 312 |
| 00:10:31,000 |
| and then you have to mention the file name. |
|
|
| 313 |
| 00:10:32,000 |
| So first you have to be make sure |
|
|
| 314 |
| 00:10:33,000 |
| that you are in a correct folder, which is close. |
|
|
| 315 |
| 00:10:36,000 |
| You can see that this is a folder we have |
|
|
| 316 |
| 00:10:38,000 |
| and then you have to mention Java C. |
|
|
| 317 |
| 00:10:39,000 |
| And then the file name. |
|
|
| 318 |
| 00:10:40,000 |
| The file name in this case is hello.Java, click on enter. |
|
|
| 319 |
| 00:10:44,000 |
| Oh, we got an error. |
|
|
| 320 |
| 00:10:46,000 |
| Okay, so it says something is missing, you know, |
|
|
| 321 |
| 00:10:48,000 |
| something else was expected |
|
|
| 322 |
| 00:10:50,000 |
| and you are giving this, this is not working. |
|
|
| 323 |
| 00:10:53,000 |
| So this is not how you write applications |
|
|
| 324 |
| 00:10:55,000 |
| or code in Java file. |
|
|
| 325 |
| 00:10:56,000 |
| We have to do something else. |
|
|
| 326 |
| 00:10:58,000 |
| But at this point we have understood right? |
|
|
| 327 |
| 00:10:59,000 |
| How do you work with Jshell? |
|
|
| 328 |
| 00:11:00,000 |
| So you can, if you want to do something with Jshell, |
|
|
| 329 |
| 00:11:01,000 |
| just write a code, it will work. |
|
|
| 330 |
| 00:11:04,000 |
| If you want to add two numbers, it will work. |
|
|
| 331 |
| 00:11:05,000 |
| You can't do that here. |
|
|
| 332 |
| 00:11:06,000 |
| We have to do something extra, and what is that something, |
|
|
| 333 |
| 00:11:10,000 |
| that we'll see in the next video. |
|
|
|
|
