1 00:00:00,290 --> 00:00:06,600 Hire everyone in the theater you will I'm going to talk about comments variabilis and primitive data 2 00:00:06,600 --> 00:00:07,220 types. 3 00:00:07,410 --> 00:00:10,490 So first I you to create our Java project. 4 00:00:10,710 --> 00:00:17,660 So first we need to click can find new and click on Java project for the project name. 5 00:00:17,660 --> 00:00:26,920 Just type in variables and I choose the default location for saving my project here and click on finish. 6 00:00:27,270 --> 00:00:29,910 And as you can see here my project is created. 7 00:00:30,070 --> 00:00:30,660 OK. 8 00:00:30,750 --> 00:00:34,060 Now we need to create a Java class for our project. 9 00:00:34,230 --> 00:00:36,470 So first click on this as RC for that. 10 00:00:36,480 --> 00:00:43,690 Or you can click on this variable's project and then click on find Neil and click on class. 11 00:00:44,100 --> 00:00:44,640 OK. 12 00:00:44,700 --> 00:00:48,120 Now we need to actually enter our last name here. 13 00:00:48,300 --> 00:00:53,790 So for the class and just type in variable and make sure that your class name starts with a capital 14 00:00:53,790 --> 00:00:54,610 letter. 15 00:00:54,750 --> 00:01:00,220 Because this is a convention in Java that all your classes should start with a capital letter. 16 00:01:00,280 --> 00:01:02,030 OK so this is really important. 17 00:01:02,290 --> 00:01:08,620 And here for the first time I really don't actually enter a package name for our package. 18 00:01:08,820 --> 00:01:15,610 And as I said earlier in this section that package is just a way to actually organize our Java files. 19 00:01:15,630 --> 00:01:16,120 OK. 20 00:01:16,290 --> 00:01:23,870 So for the package name we just need to actually type in a reverse domain so calm that Mortaza. 21 00:01:24,180 --> 00:01:30,230 OK that's an idea and we just need to actually enter our project name variables. 22 00:01:30,240 --> 00:01:31,840 OK. 23 00:01:32,010 --> 00:01:38,190 And this is a convention in Java that you should actually name your package names. 24 00:01:38,190 --> 00:01:39,190 OK. 25 00:01:39,630 --> 00:01:40,490 Like this. 26 00:01:40,580 --> 00:01:41,250 OK. 27 00:01:41,290 --> 00:01:42,460 A reverse domain. 28 00:01:42,460 --> 00:01:49,790 And at the end just enter your project name and for the modifiers just check it is a public modifier. 29 00:01:49,860 --> 00:01:54,630 And here check this checkbox here that says public is static void main method. 30 00:01:54,630 --> 00:02:00,150 This is a starting point for actually running our Java codes and click on finish. 31 00:02:00,810 --> 00:02:06,240 And here as you can see our class is created and here is our package name. 32 00:02:06,420 --> 00:02:11,290 OK this is our package name as you can see here and in our project directory. 33 00:02:11,670 --> 00:02:18,240 When you open the source folder inside the source folder there is a package and this is the package 34 00:02:18,240 --> 00:02:19,810 name as you can see here. 35 00:02:20,320 --> 00:02:21,790 And here is the same package. 36 00:02:21,830 --> 00:02:22,540 OK. 37 00:02:22,800 --> 00:02:28,380 So the package name of the class is established by the package statement. 38 00:02:28,380 --> 00:02:30,770 Ok this is our package statement. 39 00:02:30,860 --> 00:02:31,570 OK. 40 00:02:31,890 --> 00:02:37,610 Which must be the first line of a Java program when it is used. 41 00:02:37,680 --> 00:02:40,810 OK so that's it for packages. 42 00:02:41,050 --> 00:02:41,520 OK. 43 00:02:41,550 --> 00:02:43,620 Now I'm going to ask you about comments. 44 00:02:43,620 --> 00:02:47,170 So as you can see here are this line of text here is a comment. 45 00:02:47,190 --> 00:02:47,800 OK. 46 00:02:48,060 --> 00:02:55,500 I can create my own comments to for example and putting our two forward slashes and then I can actually 47 00:02:55,510 --> 00:02:56,160 type. 48 00:02:56,260 --> 00:03:00,750 I just enter what ever it takes that I want. 49 00:03:01,500 --> 00:03:06,000 Ok what ever text that I want. 50 00:03:06,170 --> 00:03:09,570 OK so what are comments. 51 00:03:09,600 --> 00:03:17,880 First let me point out that comments are one of the most effective ways to improve our programs readability. 52 00:03:17,910 --> 00:03:18,610 OK. 53 00:03:18,870 --> 00:03:25,670 These are text included in a program that explains what's going on in the code. 54 00:03:25,800 --> 00:03:26,580 OK. 55 00:03:26,580 --> 00:03:33,270 And the Java compiler is going to actually completely ignore these lines of text. 56 00:03:33,270 --> 00:03:34,860 Ok these comments. 57 00:03:34,890 --> 00:03:36,450 So what is a compiler. 58 00:03:36,690 --> 00:03:45,870 As I said in the previous section or compiler is a special software compiler is exclusive software that 59 00:03:45,870 --> 00:03:53,680 actually convert your Java code into a language that the machine can understand. 60 00:03:53,920 --> 00:04:00,880 OK so now I'm going to show you some real examples about using comments in your programs. 61 00:04:00,900 --> 00:04:07,050 So first of all I want to show you how to actually make this editor area wider in order to write our 62 00:04:07,050 --> 00:04:07,830 codes better. 63 00:04:07,860 --> 00:04:08,420 OK. 64 00:04:08,670 --> 00:04:15,770 So in order to make the is actually the editor area wider you just need to double click on this variable 65 00:04:15,770 --> 00:04:21,740 to job hop here which as you can see this little area is much wider now. 66 00:04:22,020 --> 00:04:26,780 And in order to go back to the default screen just DoubleClick is valuable over here. 67 00:04:26,940 --> 00:04:29,330 And as you can see here this is the default screen. 68 00:04:29,330 --> 00:04:29,900 OK. 69 00:04:30,240 --> 00:04:34,830 So now I want to actually out with Dave or hello to the council. 70 00:04:35,010 --> 00:04:42,210 So let's see what happens system that out princeling and inside the Apprentice it's just I just put 71 00:04:42,210 --> 00:04:46,820 in a two level codes and just type in Hello 72 00:04:49,440 --> 00:04:57,370 cake and at the end just up with a semi-colon at the end of your statement here I want to actually use 73 00:04:57,370 --> 00:05:01,630 a comment that explains what this code here is doing. 74 00:05:01,810 --> 00:05:05,190 So let's see what comments are. 75 00:05:05,530 --> 00:05:13,700 As you can see I am the one to actually I am out putting forth 76 00:05:16,430 --> 00:05:19,450 hello to the console. 77 00:05:22,720 --> 00:05:30,400 So here as you can see this comment here is just explaining what this code what this statement here 78 00:05:30,400 --> 00:05:31,200 is doing. 79 00:05:31,390 --> 00:05:31,870 OK. 80 00:05:31,990 --> 00:05:35,930 And the compiler completely ignores these comments. 81 00:05:35,980 --> 00:05:36,900 OK. 82 00:05:37,240 --> 00:05:41,340 So first let me actually run this program and let's see what happens. 83 00:05:41,530 --> 00:05:48,490 So as you can see the vault Halo is out with the console area and these comments are completely ignored 84 00:05:48,520 --> 00:05:49,550 by the compiler. 85 00:05:49,750 --> 00:05:50,250 OK. 86 00:05:50,440 --> 00:05:56,630 So it's really good to actually get into the habit of writing comments in your programs. 87 00:05:56,650 --> 00:06:02,980 It's going to make your programs more meaningful for yourself or other programs that may actually look 88 00:06:03,070 --> 00:06:04,750 at your codes in the future. 89 00:06:04,890 --> 00:06:05,530 OK. 90 00:06:05,800 --> 00:06:09,390 So always use comments in your programs. 91 00:06:09,580 --> 00:06:13,080 And we have three kinds of comments in Java. 92 00:06:13,360 --> 00:06:16,870 So first of all we have got our single line comment. 93 00:06:16,900 --> 00:06:21,250 So as you can see here these comments are called single line comments. 94 00:06:21,250 --> 00:06:21,860 OK. 95 00:06:21,910 --> 00:06:27,100 So in order to create a single line comment just putting two forward slashes and typing your text. 96 00:06:27,100 --> 00:06:32,690 For example this is called This is called a single line comment. 97 00:06:35,560 --> 00:06:41,720 And everything from the slushes forward as you can see here is called the comment and it's going to 98 00:06:41,720 --> 00:06:44,290 be completely ignored by the compiler. 99 00:06:44,300 --> 00:06:44,870 OK. 100 00:06:45,000 --> 00:06:48,050 Another type of comment is a multi-line comment. 101 00:06:48,050 --> 00:06:54,350 So for example if you want to create a multi-line comment in my program I just need to start my multi-line 102 00:06:54,350 --> 00:07:03,320 comment with a forward slash and multiply operator and that I need to actually end my multi-line comment 103 00:07:03,560 --> 00:07:07,080 with the multiply operator and a forward slash. 104 00:07:07,190 --> 00:07:08,540 So this is very important. 105 00:07:08,660 --> 00:07:14,480 You need to actually start your model and comment with a forward slash and then multiply operator or 106 00:07:14,480 --> 00:07:16,560 the star symbol as you can see here. 107 00:07:16,940 --> 00:07:20,470 And then we need to end our multi-line comment. 108 00:07:20,730 --> 00:07:28,580 Multiply operator and forward slash So everything between these two delimiters is considered a comment. 109 00:07:28,670 --> 00:07:34,670 So for example if I just press on the Enter key on my keyboard as you can see here I can actually put 110 00:07:34,670 --> 00:07:37,760 in my text here so I can just type in here. 111 00:07:37,760 --> 00:07:45,240 This is called Amante line comment as you can see here. 112 00:07:45,440 --> 00:07:45,890 OK. 113 00:07:47,590 --> 00:07:55,780 So this text this line of this line of text here is completely ignored by the compiler or the compiler 114 00:07:55,780 --> 00:08:00,920 is going to ignore everything that we hide between these two delimiters. 115 00:08:00,940 --> 00:08:01,650 OK. 116 00:08:01,690 --> 00:08:05,080 The last type of comments is called Javadoc comments. 117 00:08:05,090 --> 00:08:05,620 OK. 118 00:08:05,770 --> 00:08:12,910 For example if I want to create a job with comments in my program first I just need to begin my Java 119 00:08:13,180 --> 00:08:20,440 comment with a forward slash and to multiply operators and then I need to end my job what I comment 120 00:08:20,840 --> 00:08:24,320 with the multiply operator and our forward slash. 121 00:08:24,550 --> 00:08:31,240 So as you can see here everything between these two delimiters is considered a Java like comment. 122 00:08:31,240 --> 00:08:37,720 OK so for example if I again present Enter key on my keyboard as you can see here I can type in here 123 00:08:37,720 --> 00:08:38,620 anything that I want. 124 00:08:38,620 --> 00:08:40,650 For example I can type in here. 125 00:08:40,660 --> 00:08:49,790 This is called Java that comment Java dodge comment. 126 00:08:50,580 --> 00:08:51,560 OK. 127 00:08:51,780 --> 00:08:59,820 But we don't use actually Obstat comments in our programs and Jodo comments are designed to be read 128 00:08:59,880 --> 00:09:04,380 by utilities such as job attach a command line tool. 129 00:09:04,500 --> 00:09:07,180 That's part of Java Development Kit JDK. 130 00:09:07,270 --> 00:09:07,880 OK. 131 00:09:08,100 --> 00:09:15,550 This tool uses official comments to create a set of web pages that document that the functionality of 132 00:09:15,620 --> 00:09:17,280 of a Java class. 133 00:09:17,280 --> 00:09:17,860 OK. 134 00:09:18,240 --> 00:09:20,250 So we don't actually use this. 135 00:09:20,450 --> 00:09:23,790 This Java comment a lot in our programs. 136 00:09:24,000 --> 00:09:24,310 OK. 137 00:09:24,330 --> 00:09:29,390 But later I want to show you more about comments in our programs for example. 138 00:09:29,670 --> 00:09:38,280 If I don't want to actually execute this line of code here for example if I run my program now you can 139 00:09:38,280 --> 00:09:44,160 see that it's going to show me the hello text here but if I don't want to actually execute this line 140 00:09:44,160 --> 00:09:47,550 of code I can easily comment out this line of code. 141 00:09:47,900 --> 00:09:48,560 OK. 142 00:09:48,870 --> 00:09:55,380 Now you can see that if I run my program it's going to show me nothing because this this statement is 143 00:09:55,380 --> 00:09:56,680 now commented out. 144 00:09:56,700 --> 00:09:57,360 OK.