1 00:00:00,450 --> 00:00:08,370 So as you can see here in this line of code I just declared this valuable and here I referred to the 2 00:00:08,370 --> 00:00:12,900 name of my valuable and I assigned a value to my value. 3 00:00:13,050 --> 00:00:16,700 And here I referred to this now free variable. 4 00:00:16,830 --> 00:00:20,430 And I just create the value of this variable. 5 00:00:20,520 --> 00:00:21,200 OK. 6 00:00:21,510 --> 00:00:29,790 But if I for example want to refer to this are now very valuable here as you can see here now free. 7 00:00:29,830 --> 00:00:30,250 OK. 8 00:00:30,390 --> 00:00:32,360 As you can see it's not showing me an error. 9 00:00:32,400 --> 00:00:33,780 So let's see what's this error. 10 00:00:33,990 --> 00:00:38,040 Now free cannot be resolved as you can see here. 11 00:00:38,280 --> 00:00:41,180 It's not recognizing there are no free variable. 12 00:00:41,420 --> 00:00:42,010 OK. 13 00:00:42,090 --> 00:00:46,510 Because I declared this now free variable in line 52. 14 00:00:46,560 --> 00:00:47,030 OK. 15 00:00:47,130 --> 00:00:51,450 And I am referring to this not everybody but in line 50. 16 00:00:51,570 --> 00:00:58,010 So you must actually refer to a variable that was created before. 17 00:00:58,140 --> 00:00:58,810 OK. 18 00:00:59,070 --> 00:01:05,440 For example if I created this variable here I just can't refer to this the name of this variable here. 19 00:01:05,580 --> 00:01:08,410 All the lines after the creation of this variable. 20 00:01:08,430 --> 00:01:09,080 OK. 21 00:01:09,330 --> 00:01:13,940 You can't refer to a variable before the creation of that variable. 22 00:01:14,010 --> 00:01:18,380 Ok this is very important and I'll touch more about this concept later. 23 00:01:18,800 --> 00:01:19,550 OK. 24 00:01:19,770 --> 00:01:23,770 Now I'm going to talk about naming variables in Java. 25 00:01:23,880 --> 00:01:24,500 OK. 26 00:01:24,720 --> 00:01:31,400 So first let me comment about this line of code because I don't want to execute this statement any more. 27 00:01:31,410 --> 00:01:40,020 First of all let me point out that in Java all variable names must start with a letter and underscore 28 00:01:40,020 --> 00:01:42,000 character at the other side. 29 00:01:41,990 --> 00:01:42,610 OK. 30 00:01:42,870 --> 00:01:49,440 Variable names can not start with a number you cannot start your variable names with a number. 31 00:01:49,440 --> 00:01:56,550 This is a very important point in name and your valuables after the first character variable names can 32 00:01:56,550 --> 00:02:02,450 include any combination of letters numbers underscore characters or Dollar Signs. 33 00:02:02,530 --> 00:02:10,560 OK now let me show you some real examples about naming variables in Java to make this concept more clear 34 00:02:10,560 --> 00:02:11,070 for you. 35 00:02:11,070 --> 00:02:18,400 OK so as you can see here I'm going to declare a variable here so the data type of my variable is int. 36 00:02:18,420 --> 00:02:19,950 This ain't data type. 37 00:02:19,950 --> 00:02:25,530 Here means that my variable holds an integer or a whole number. 38 00:02:25,550 --> 00:02:28,860 OK so now I'm going to actually name my value. 39 00:02:29,130 --> 00:02:38,520 So as I said earlier variable names in Java must start with the letter and underscore character or a 40 00:02:38,520 --> 00:02:39,220 dollar sign. 41 00:02:39,270 --> 00:02:43,740 OK so now I am going to actually start my variable name with the letter. 42 00:02:44,070 --> 00:02:47,570 So for example a valuable. 43 00:02:48,030 --> 00:02:53,350 Ok now I'm going to assign a value to my variable for example not per number 30. 44 00:02:53,570 --> 00:03:00,150 OK so as you can see here I start at my variable name with a lowercase letter. 45 00:03:00,330 --> 00:03:07,470 As you can see so this is a convention in Java that you should actually start your variable names with 46 00:03:07,470 --> 00:03:08,620 a lowercase letter. 47 00:03:08,670 --> 00:03:15,420 OK you can actually start your variable name with the uppercase letter as you can see here but it's 48 00:03:15,420 --> 00:03:19,900 better to actually declare your variable names with a lower case letter. 49 00:03:19,930 --> 00:03:26,680 OK because this is a convention in Java that you should always start your variable names with a lowercase 50 00:03:26,690 --> 00:03:28,150 Slidder OK. 51 00:03:28,440 --> 00:03:35,340 And as you can see here my variable name here starts with a lowercase letter. 52 00:03:35,580 --> 00:03:40,220 So the first letter of the variable name is lowercase. 53 00:03:40,230 --> 00:03:40,930 OK. 54 00:03:41,370 --> 00:03:47,870 And each successive forth in the variable name begins with a capital letter. 55 00:03:47,880 --> 00:03:55,560 So as you can see here this valuable vote here starts with a capital V OK and if I want to for example 56 00:03:56,010 --> 00:03:57,890 add another vote here. 57 00:03:58,110 --> 00:04:00,950 For example a variable name. 58 00:04:01,360 --> 00:04:03,790 OK so let's see what happens. 59 00:04:04,380 --> 00:04:13,410 As you can see I started this vort this and then vote here with a capital N. and all other letters are 60 00:04:13,560 --> 00:04:14,960 lowercase. 61 00:04:14,970 --> 00:04:21,760 So to recap as you can see here the first letter of the variable name is lowercase. 62 00:04:22,050 --> 00:04:24,770 So this a letter is lowercase OK. 63 00:04:25,320 --> 00:04:32,310 And each successive board in the variable name begins with a capital letter. 64 00:04:32,360 --> 00:04:37,360 It is valuable word and this name vord begins with a capital letter. 65 00:04:37,380 --> 00:04:43,130 As you can see here and all other letters are lower case. 66 00:04:43,140 --> 00:04:45,240 So let me show you another example. 67 00:04:45,610 --> 00:04:51,270 Again the data type is int and the variable name would be another 68 00:04:54,590 --> 00:04:58,380 is declared here. 69 00:04:58,940 --> 00:05:00,130 As you can see here. 70 00:05:00,230 --> 00:05:02,840 This variable name is a very long name. 71 00:05:03,020 --> 00:05:08,730 OK it is acceptable in Java that you actually write Longueval names. 72 00:05:08,750 --> 00:05:10,210 If it is it is OK. 73 00:05:10,340 --> 00:05:15,400 There is no problem about it and that I can't assign a value to my variable. 74 00:05:15,500 --> 00:05:26,570 For example 23 and here are the first letter of my variable name begins with a lowercase letter and 75 00:05:26,690 --> 00:05:32,820 each successive vote in the variable name begins with a capital letter. 76 00:05:32,840 --> 00:05:38,020 OK this variable is declared here as you can see these. 77 00:05:38,600 --> 00:05:41,980 Start with a capital letter OK. 78 00:05:42,170 --> 00:05:45,530 And all other letters are lowercase. 79 00:05:45,530 --> 00:05:51,650 OK this is a convention in Java that you should always actually name your valuables this way. 80 00:05:51,720 --> 00:06:01,940 OK and let me show you another examples this time again the data type would be int here. 81 00:06:01,940 --> 00:06:06,680 I'm going to start my variable name with the underscore character. 82 00:06:07,190 --> 00:06:11,420 And again I need to actually start my other votes. 83 00:06:11,450 --> 00:06:15,710 Each successive vote in the variable name with a capital letter. 84 00:06:15,830 --> 00:06:19,040 Ok for example are there 85 00:06:23,100 --> 00:06:26,350 and again I can't assign a value to my value. 86 00:06:26,980 --> 00:06:32,190 It is OK to actually start your variable names with the underscore character. 87 00:06:32,740 --> 00:06:40,050 And again I'm going to actually show you another example this time the data type is again integer Int. 88 00:06:40,240 --> 00:06:44,500 And does that mean we're going to start my variable name with a dollar sign. 89 00:06:44,590 --> 00:06:45,660 OK. 90 00:06:46,090 --> 00:06:52,100 I can actually type in here other words for example dollar sign value. 91 00:06:54,880 --> 00:06:58,120 And again I can assign values to my variable. 92 00:06:58,150 --> 00:06:59,470 For example for free. 93 00:06:59,530 --> 00:07:00,170 OK. 94 00:07:00,430 --> 00:07:05,030 So as you can see here this variable name here starts with a dollar sign. 95 00:07:05,200 --> 00:07:11,130 And each successive word in the value of a name begins with the uppercase letter. 96 00:07:11,200 --> 00:07:11,950 OK. 97 00:07:12,340 --> 00:07:19,360 So this is how you actually declare actually your variable names in Java and you should always as I 98 00:07:19,360 --> 00:07:28,180 said before all your variable names must start with the letter and underscore character or a dollar 99 00:07:28,170 --> 00:07:28,500 sign. 100 00:07:28,540 --> 00:07:28,780 OK. 101 00:07:28,780 --> 00:07:33,150 You can't actually start your variable name with the number. 102 00:07:33,280 --> 00:07:36,210 So let me show you what's what's the problem with that. 103 00:07:36,290 --> 00:07:43,000 With actually naming your valuables like that as you can see the data type is int and I'm going to actually 104 00:07:43,000 --> 00:07:46,430 declare my variable name here. 105 00:07:46,630 --> 00:07:52,770 For example 21 variable name J. 106 00:07:53,050 --> 00:07:59,590 And then I can assign a value to my variable and then I just need to put a semicolon at the end of her 107 00:07:59,590 --> 00:08:00,610 statement. 108 00:08:00,610 --> 00:08:08,830 So let's actually run our project and here as you can see it says errors exist in required projects. 109 00:08:08,980 --> 00:08:10,410 This project variables. 110 00:08:10,600 --> 00:08:13,610 So we can't actually launch our project now. 111 00:08:13,660 --> 00:08:14,660 There must be an error. 112 00:08:14,680 --> 00:08:15,260 OK. 113 00:08:15,460 --> 00:08:24,040 So as you can see here if I hover over my mouse pointer over the error area here as you can see it says 114 00:08:24,160 --> 00:08:27,240 syntax error on token 21. 115 00:08:27,280 --> 00:08:28,640 Delete this token. 116 00:08:29,080 --> 00:08:36,380 So as you can see here it asks us to actually delete this number 21 at the start of our variable name. 117 00:08:36,490 --> 00:08:44,650 So now let's just actually delete this number 21 at the start of our variable name and let's see what 118 00:08:44,650 --> 00:08:45,800 happens. 119 00:08:46,360 --> 00:08:49,680 And as you can see here now the error is gone. 120 00:08:49,990 --> 00:08:53,160 And now I can actually run my project. 121 00:08:53,170 --> 00:08:53,790 OK. 122 00:08:54,100 --> 00:09:01,330 So if I for example want to output the value of this variable name to the canso I can just type in system 123 00:09:02,560 --> 00:09:05,110 that out that print line. 124 00:09:05,710 --> 00:09:07,430 And that inside the parenthesis. 125 00:09:07,510 --> 00:09:11,580 I just need to refer to this variable name here. 126 00:09:12,110 --> 00:09:12,950 Variable name 127 00:09:16,950 --> 00:09:21,590 and that I just need to put a semi-colon at the end of our Actually statement. 128 00:09:21,600 --> 00:09:22,350 OK. 129 00:09:23,010 --> 00:09:32,600 So here I just need to run my project as you can see it's now actually showing us the number 42 on the 130 00:09:32,610 --> 00:09:33,920 console here. 131 00:09:34,230 --> 00:09:38,160 So the number 42 is the value of this variable name. 132 00:09:38,330 --> 00:09:39,120 OK. 133 00:09:39,750 --> 00:09:42,020 So that's it for variables. 134 00:09:42,030 --> 00:09:45,530 I think that's enough for valuables.