1 00:00:00,090 --> 00:00:01,390 This video is for Mac. 2 00:00:01,410 --> 00:00:04,800 If you're using a Windows computer, please go to the next lesson. 3 00:00:06,650 --> 00:00:09,410 Every developer should know how to use their terminal. 4 00:00:11,730 --> 00:00:14,820 So far, you learned how to run your code using the run button. 5 00:00:15,060 --> 00:00:19,530 Now, the run button is nice, but it's really important that you learn how to use your terminal. 6 00:00:22,380 --> 00:00:26,250 So in this lesson, you will run your code using terminal commands. 7 00:00:28,790 --> 00:00:31,640 Java C means Java compiler. 8 00:00:33,800 --> 00:00:39,890 So in step one, the Terminal command Java C is going to compile your Java code into bytecode. 9 00:00:43,710 --> 00:00:47,670 Specifically, we want to compile the code inside of Helo Java Java. 10 00:00:50,990 --> 00:00:57,380 So tell your terminal we want the Java compiler Java C to compile the code inside of Hello, Java. 11 00:00:57,650 --> 00:00:58,310 Java. 12 00:01:01,090 --> 00:01:07,420 By doing so, the Java compiler will compile all of the Java code into a format called Bytecode. 13 00:01:09,420 --> 00:01:13,140 The compiled bytecode is going to live inside of a dot class file. 14 00:01:16,330 --> 00:01:17,230 From Vsco. 15 00:01:17,230 --> 00:01:20,290 You can open up a new terminal by going over to terminal. 16 00:01:20,440 --> 00:01:21,430 New terminal. 17 00:01:22,750 --> 00:01:26,230 If the debug console shows up for you, feel free to dismiss it. 18 00:01:27,000 --> 00:01:34,680 And your terminal should automatically point to section one the Hello Java Java file that lives inside 19 00:01:34,680 --> 00:01:35,550 of Section one. 20 00:01:35,550 --> 00:01:38,420 So over here we can compile the code inside of it. 21 00:01:38,430 --> 00:01:40,380 Java Compiler and Java C. 22 00:01:41,590 --> 00:01:43,330 And now press tab. 23 00:01:44,000 --> 00:01:45,140 By pressing tab. 24 00:01:45,140 --> 00:01:49,810 It guesses the file that I'm trying to compile by looking inside of the folder Section one. 25 00:01:49,820 --> 00:01:53,110 There's only one file inside of section one so it auto completes. 26 00:01:53,120 --> 00:01:53,450 Hello. 27 00:01:53,450 --> 00:01:53,930 Java. 28 00:01:53,930 --> 00:01:54,500 Java. 29 00:01:55,940 --> 00:01:58,460 And now you can compile your Java code. 30 00:02:04,990 --> 00:02:11,740 But anyways, by applying the Java Command on our Java file, the Java compiler compiled all of its 31 00:02:11,740 --> 00:02:16,720 Java code into byte code, and the byte code lives inside of a dot class file. 32 00:02:20,250 --> 00:02:25,440 In step number two, the Terminal command Java executes the compiled code. 33 00:02:28,940 --> 00:02:33,020 So to summarize, the Java Sea Command compiles your code. 34 00:02:34,680 --> 00:02:39,020 And the Java Command executes the compiled code by design. 35 00:02:39,030 --> 00:02:42,290 The Java Sea Command includes the Java extension. 36 00:02:42,300 --> 00:02:44,460 The Java Command does not. 37 00:02:44,490 --> 00:02:48,120 So please be very careful when writing your commands. 38 00:02:48,780 --> 00:02:50,400 All right, Back to our project. 39 00:02:50,400 --> 00:02:53,880 We will write Java and then press tab. 40 00:02:53,910 --> 00:02:57,720 It's going to autocomplete based on what it finds inside of Section one. 41 00:02:57,750 --> 00:03:00,900 Do not add a Java extension at the end. 42 00:03:02,000 --> 00:03:05,300 Just like that, it's able to run the compiled code. 43 00:03:07,080 --> 00:03:12,210 What these two commands are doing is pretty much what the run button was doing for us behind the scenes. 44 00:03:12,210 --> 00:03:16,950 But I want you to be comfortable running terminal commands, so I'm going to keep using terminal commands 45 00:03:16,950 --> 00:03:18,210 throughout this course. 46 00:03:18,420 --> 00:03:23,960 Now, let's say I want to re execute the compiled code instead of rewriting this command. 47 00:03:23,970 --> 00:03:26,070 What I can do is press the up key. 48 00:03:26,310 --> 00:03:31,560 The up key remembers previous terminal commands and we can use it to re execute the compiled code as 49 00:03:31,560 --> 00:03:33,120 many times as we want. 50 00:03:33,980 --> 00:03:34,700 Awesome. 51 00:03:37,210 --> 00:03:42,850 Remember that when you execute your code, Java looks for the entry point main, it tries to find it 52 00:03:42,850 --> 00:03:48,360 and once it finds main, it runs the code inside the first line of code inside main prints. 53 00:03:48,370 --> 00:03:49,480 Hello Java. 54 00:03:49,930 --> 00:03:54,670 Then it looks for more code inside main, but there isn't any so it reaches the end. 55 00:03:55,600 --> 00:03:56,130 All right. 56 00:03:56,140 --> 00:04:00,520 With that being said, I need to warn you to always compile your code first. 57 00:04:01,190 --> 00:04:07,670 When you make changes to your code, compile it first using Java C and then run the compiled code using 58 00:04:07,670 --> 00:04:08,960 the Java Command. 59 00:04:09,590 --> 00:04:16,190 Let's look at an example where I don't do that, so I'm going to change the message to Greetings Java. 60 00:04:18,459 --> 00:04:23,050 And now I would expect that by running this code, it should print this message. 61 00:04:23,290 --> 00:04:26,440 So just run the code without compiling Java. 62 00:04:26,470 --> 00:04:26,830 Hello? 63 00:04:26,830 --> 00:04:27,490 Java. 64 00:04:30,710 --> 00:04:31,640 And it still prints. 65 00:04:31,640 --> 00:04:32,450 Hello, Java. 66 00:04:32,450 --> 00:04:35,870 And that's because you're running the old compiled code. 67 00:04:36,720 --> 00:04:41,430 When you make changes to your code, you need to recompile it using Java Sea. 68 00:04:41,850 --> 00:04:42,650 Java Sea. 69 00:04:42,720 --> 00:04:43,140 Hello? 70 00:04:43,140 --> 00:04:43,500 Java. 71 00:04:43,710 --> 00:04:44,370 Java. 72 00:04:47,970 --> 00:04:51,840 And then execute the newly compiled code with the Java Command. 73 00:04:52,050 --> 00:04:52,680 Java. 74 00:04:52,680 --> 00:04:53,730 Hello, Java. 75 00:04:54,300 --> 00:04:57,210 And once you do that, it executes the new code. 76 00:04:58,500 --> 00:05:00,330 With that being said, congratulations. 77 00:05:00,330 --> 00:05:03,150 You executed your code using Java commands. 78 00:05:03,240 --> 00:05:07,080 So far you learn that all of your code must exist in a Java class. 79 00:05:07,470 --> 00:05:09,840 You created a class called Hello Java. 80 00:05:10,690 --> 00:05:12,070 Manage the entry point. 81 00:05:12,070 --> 00:05:14,230 This is where Java starts running your code. 82 00:05:19,190 --> 00:05:25,250 And finally, you can use the Java Sea Command to compile your code and the Java Command to execute 83 00:05:25,250 --> 00:05:26,420 the compiled code.