1 00:00:00,210 --> 00:00:01,890 This video is for Windows. 2 00:00:01,890 --> 00:00:05,430 If you're using a mac computer, please go to the previous lesson. 3 00:00:06,710 --> 00:00:07,340 So far. 4 00:00:07,340 --> 00:00:13,370 You installed Visual Studio Code, a text editor where you can write code and you installed Java inside 5 00:00:13,370 --> 00:00:14,120 your computer. 6 00:00:14,120 --> 00:00:16,309 So now you can run Java code. 7 00:00:17,040 --> 00:00:17,850 In this lesson. 8 00:00:17,850 --> 00:00:19,800 That's exactly what you're going to do. 9 00:00:19,830 --> 00:00:22,770 You will write and run your first Java code. 10 00:00:24,710 --> 00:00:26,750 Step one is to create a folder. 11 00:00:28,950 --> 00:00:31,170 Simple enough inside of your desktop. 12 00:00:31,170 --> 00:00:32,970 Make a new folder. 13 00:00:33,840 --> 00:00:36,270 And call the folder section. 14 00:00:37,820 --> 00:00:38,540 One. 15 00:00:40,310 --> 00:00:43,280 This folder is going to contain your Java file. 16 00:00:45,450 --> 00:00:48,930 Step two is to launch the folder from Visual Studio Code. 17 00:00:49,350 --> 00:00:51,090 Here I have Visual Studio code. 18 00:00:51,090 --> 00:00:51,660 Open. 19 00:00:51,690 --> 00:00:54,750 Go to file open folder. 20 00:00:55,830 --> 00:00:58,230 Find the section one folder that you just created. 21 00:00:58,230 --> 00:01:03,480 Mine is inside of desktop and here select the folder section one. 22 00:01:03,480 --> 00:01:07,080 Once you select it, press select folder in order to launch it. 23 00:01:16,090 --> 00:01:18,400 Step three is to create a Java file. 24 00:01:20,540 --> 00:01:25,730 When creating your Java file, you must name it using the camel case format where the first letter of 25 00:01:25,730 --> 00:01:29,840 every word is capitalized and the words themselves are joined together. 26 00:01:30,830 --> 00:01:31,670 And your file. 27 00:01:31,670 --> 00:01:36,770 For it to be considered a Java file, it needs to end with the extension Java. 28 00:01:38,730 --> 00:01:39,750 Let's do just that. 29 00:01:39,750 --> 00:01:46,170 I'm going to create a new file by pressing the plus icon, and the file is going to be called Hello 30 00:01:46,170 --> 00:01:52,530 Java again using Camel case, where the first letter of every word is capitalized, followed by the 31 00:01:52,530 --> 00:01:54,210 DOT Java extension. 32 00:01:54,870 --> 00:01:57,330 And here we've created a hello Java file. 33 00:01:57,330 --> 00:01:58,050 Beautiful. 34 00:02:00,420 --> 00:02:04,020 Step four is to create a Java class inside the Java file. 35 00:02:05,480 --> 00:02:06,080 In Java. 36 00:02:06,080 --> 00:02:08,780 You will write all of your code in a class. 37 00:02:10,930 --> 00:02:13,810 And there are two parts to a class the class keyword. 38 00:02:15,030 --> 00:02:16,680 Followed by the class name. 39 00:02:18,170 --> 00:02:20,750 Inside brackets is where you would write your code. 40 00:02:23,160 --> 00:02:27,330 And furthermore, the class name needs to always match the file name that it's in. 41 00:02:28,650 --> 00:02:34,440 So if the file name is called Hello, Java and Java, the corresponding class is Hello, Java. 42 00:02:36,750 --> 00:02:39,630 Inside your Java file, you can create your Java class. 43 00:02:39,630 --> 00:02:41,610 So start with the class keyword. 44 00:02:42,390 --> 00:02:44,150 Followed by the class name itself. 45 00:02:44,160 --> 00:02:45,390 Hello, Java. 46 00:02:47,000 --> 00:02:50,270 And inside brackets is where you're going to write all of your code. 47 00:02:51,030 --> 00:02:51,530 Perfect. 48 00:02:51,540 --> 00:02:53,000 We made a lot of progress. 49 00:02:53,010 --> 00:02:54,840 Let us delete all of our progress. 50 00:02:54,840 --> 00:02:56,640 We're going to delete our Java file. 51 00:02:56,640 --> 00:02:57,630 But wait a second. 52 00:02:57,630 --> 00:02:58,080 Ran. 53 00:02:58,080 --> 00:03:01,170 We made all of this progress, and now we're just going to delete it. 54 00:03:01,260 --> 00:03:02,310 Just trust me. 55 00:03:02,310 --> 00:03:04,620 So go here, delete your file. 56 00:03:13,200 --> 00:03:15,470 Because we already created a Java file. 57 00:03:15,480 --> 00:03:19,860 Now these code knows that this workspace is meant for Java development. 58 00:03:19,860 --> 00:03:24,090 So the second time we create a Java file, remember to use camel case. 59 00:03:24,630 --> 00:03:30,150 Now VS code is ready and it's going to auto generate the class for you by default. 60 00:03:30,150 --> 00:03:36,960 It adds a public keyword which makes our Hello Java class publicly accessible to other classes that 61 00:03:36,960 --> 00:03:39,240 may exist inside of this workspace. 62 00:03:39,690 --> 00:03:44,340 But there are no other classes in this workspace, so public is not really doing anything. 63 00:03:44,580 --> 00:03:46,680 You can keep it, you can remove it. 64 00:03:46,680 --> 00:03:47,700 It doesn't really matter. 65 00:03:47,700 --> 00:03:48,570 It's up to you. 66 00:03:48,750 --> 00:03:50,190 I'm just going to keep it. 67 00:03:53,540 --> 00:03:56,570 Step five Your class needs a main method. 68 00:03:58,550 --> 00:04:01,300 Maine is the entry point of a Java application. 69 00:04:01,310 --> 00:04:04,800 This is where Java starts running your code when you run your application. 70 00:04:04,820 --> 00:04:09,680 Java starts by looking for the main method so inside of your class. 71 00:04:10,370 --> 00:04:15,770 Press enter after the first bracket to get proper indentation and then right main. 72 00:04:16,339 --> 00:04:17,779 Choose the first option. 73 00:04:18,829 --> 00:04:23,390 And by clicking this option, the code automatically writes the main method for you. 74 00:04:23,780 --> 00:04:28,880 Now, this might look like a lot of code and it might look a bit scary, but rest assured, the main 75 00:04:28,880 --> 00:04:30,860 method always looks like this. 76 00:04:30,980 --> 00:04:33,850 All you need to know is that this is the entry point. 77 00:04:33,860 --> 00:04:36,290 This is where Java starts running your code. 78 00:04:36,590 --> 00:04:41,800 Inside of Main, we're going to print a message and you can do this using the print line function. 79 00:04:41,810 --> 00:04:42,950 So system. 80 00:04:43,660 --> 00:04:46,420 Dot out dot print line. 81 00:04:48,120 --> 00:04:50,710 Instead of double quotes, I'm going to write. 82 00:04:50,730 --> 00:04:52,650 Hello, Java. 83 00:04:57,290 --> 00:05:00,410 Before we do anything else, let's break this line of code down. 84 00:05:00,440 --> 00:05:03,710 Print line is a function that prints a message to the console. 85 00:05:05,420 --> 00:05:08,900 In parentheses is where you place the message that you want to print. 86 00:05:10,550 --> 00:05:13,010 And the semi-colon is very important. 87 00:05:13,100 --> 00:05:15,740 The semicolon means end of statement. 88 00:05:15,770 --> 00:05:20,120 Every statement in Java, every line of code needs a semicolon at the end. 89 00:05:21,840 --> 00:05:23,790 If you forget your semicolon. 90 00:05:25,880 --> 00:05:28,400 Java is going to throw a big red error. 91 00:05:28,400 --> 00:05:33,050 If you hover on the error, it tells you that you forgot a semicolon, so you need to insert it. 92 00:05:35,510 --> 00:05:36,860 On the topic of errors. 93 00:05:36,860 --> 00:05:40,130 If you misspell the function, you're going to get an error. 94 00:05:40,340 --> 00:05:42,680 Java has no idea what function this is. 95 00:05:42,680 --> 00:05:44,750 It has no idea what you're talking about. 96 00:05:48,560 --> 00:05:53,150 And last but not least, code in any programming language is sensitive. 97 00:05:55,390 --> 00:06:00,160 If you capitalize a letter that shouldn't be capitalized, you're also going to get an error. 98 00:06:00,190 --> 00:06:04,900 Java does not recognize the print capital T function, so please be careful. 99 00:06:04,900 --> 00:06:07,420 Your syntax needs to always be exact. 100 00:06:07,420 --> 00:06:09,220 It needs to always be perfect. 101 00:06:10,820 --> 00:06:14,510 And you'll remember that the class name needs to always match the file name. 102 00:06:14,900 --> 00:06:21,110 So if I were to misspell the class by capitalizing a random letter that I shouldn't here, Java tells 103 00:06:21,110 --> 00:06:26,540 us that this class name does not match the file name that it's in, so we need to fix it. 104 00:06:31,270 --> 00:06:34,720 So please make sure that your syntax is always exact. 105 00:06:35,850 --> 00:06:38,310 Step six is to turn on autosave. 106 00:06:39,530 --> 00:06:42,500 The white dot means that you have unsaved changes. 107 00:06:42,500 --> 00:06:45,080 So what you would do is go to file. 108 00:06:45,860 --> 00:06:47,420 And then press save. 109 00:06:48,230 --> 00:06:50,000 Now your file is saved. 110 00:06:50,000 --> 00:06:54,830 And if I were to change the string, for example, if I were to add a bunch of exclamation marks. 111 00:06:58,100 --> 00:06:59,810 The white dot reappears. 112 00:07:02,600 --> 00:07:04,880 And now I have to save my code again. 113 00:07:05,120 --> 00:07:08,570 Now, this can be a bit annoying, so just turn on autosave. 114 00:07:09,910 --> 00:07:14,200 And now every time I make changes, the application saves by itself. 115 00:07:16,200 --> 00:07:18,270 The final step is to run your application. 116 00:07:18,270 --> 00:07:24,090 So once you're certain that your code is good, there are no syntax errors, there are no red underlines. 117 00:07:24,090 --> 00:07:26,970 You can execute it the run button. 118 00:07:26,970 --> 00:07:28,110 Execute your code. 119 00:07:34,850 --> 00:07:35,610 And there you go. 120 00:07:35,630 --> 00:07:37,160 It prints out our message. 121 00:07:39,970 --> 00:07:45,160 When you execute your code, Java looks for the entry point, it looks for main tries to find it, and 122 00:07:45,160 --> 00:07:47,920 once it does, it's going to run the code inside. 123 00:07:48,100 --> 00:07:50,580 The first line of code inside main prints. 124 00:07:50,590 --> 00:07:51,650 Hello Java. 125 00:07:51,670 --> 00:07:56,440 Then it looks for more code inside main, but there isn't any, so it reaches the end. 126 00:08:00,550 --> 00:08:05,440 If you have any syntax errors, your code is not going to run. 127 00:08:10,700 --> 00:08:10,970 Here. 128 00:08:10,970 --> 00:08:15,950 It's telling me that I have an error inside of line number four and I need to fix it. 129 00:08:18,780 --> 00:08:20,370 If I rerun my code now. 130 00:08:21,870 --> 00:08:23,310 It works beautifully. 131 00:08:23,310 --> 00:08:26,910 And now I can keep running my code to my heart's content. 132 00:08:28,390 --> 00:08:29,320 All right. 133 00:08:35,530 --> 00:08:37,570 With that being said, congratulations. 134 00:08:37,570 --> 00:08:40,360 You wrote and ran your first Java code. 135 00:08:41,880 --> 00:08:46,130 In this lesson, you learn that all of your code must exist in a Java class. 136 00:08:46,140 --> 00:08:47,790 You created a class called Hello. 137 00:08:47,790 --> 00:08:50,360 Java Main is the entry point. 138 00:08:50,370 --> 00:08:52,950 This is where Java starts running your code.