1 00:00:00,540 --> 00:00:03,880 So does that name assignment operator name. 2 00:00:04,060 --> 00:00:11,510 OK the start screen assignment operator screen the start keyboard assignment operator keyboard. 3 00:00:11,550 --> 00:00:12,220 OK. 4 00:00:12,600 --> 00:00:15,710 So now it's actually adding some more lines of code here. 5 00:00:15,720 --> 00:00:20,850 So here I'm going to pasting some lines of code and then I'm going to explain to you what's going on 6 00:00:20,850 --> 00:00:21,120 here. 7 00:00:21,120 --> 00:00:21,880 OK. 8 00:00:22,170 --> 00:00:25,930 So here as you can see these are the lines of code that they actually pasted here. 9 00:00:25,950 --> 00:00:31,680 First of all I actually created a get here good name for this unnamed instance variable. 10 00:00:32,070 --> 00:00:36,180 And then I actually created a getter again for this screen instance variable. 11 00:00:36,180 --> 00:00:36,770 OK. 12 00:00:37,110 --> 00:00:43,440 And finally I created a get keyboard Moffit get here for these keyboard instance variable and notice 13 00:00:43,440 --> 00:00:50,250 that I didn't actually create setters for this instance variables because these instance variables are 14 00:00:50,250 --> 00:00:52,830 actually declared as actually final. 15 00:00:53,100 --> 00:00:54,700 And these are constants. 16 00:00:54,730 --> 00:01:01,130 OK so once we assign a value to these instance variables we cannot change that value later. 17 00:01:01,260 --> 00:01:07,950 OK so we don't need to actually create setters for these instance variables that are actually declared 18 00:01:07,980 --> 00:01:08,790 as final. 19 00:01:08,830 --> 00:01:16,070 OK so now let's actually override the two string Meffert that we actually inherit from the Object class. 20 00:01:16,080 --> 00:01:16,460 OK. 21 00:01:16,560 --> 00:01:23,520 So this computer class implicitly inherits all of the features and behaviors that are inside of the 22 00:01:23,610 --> 00:01:24,960 inside of the Object class. 23 00:01:25,050 --> 00:01:31,440 So if we can access the string method here two string and now as you can see we can overwrite these 24 00:01:31,440 --> 00:01:32,220 two string Meffert. 25 00:01:32,220 --> 00:01:32,700 OK. 26 00:01:32,760 --> 00:01:36,310 So let's actually delete this line of code here that says Return a super. 27 00:01:36,300 --> 00:01:37,250 That was strange. 28 00:01:37,470 --> 00:01:41,820 And now we can actually put in our own implementations inside of this method. 29 00:01:41,910 --> 00:01:46,710 So here I'm going to actually paste in a line of code here and then I'm going to explain to you what's 30 00:01:46,710 --> 00:01:47,960 going on here. 31 00:01:48,000 --> 00:01:53,250 So here I am saying that the return string data format and here in say that these double quotes I am 32 00:01:53,250 --> 00:01:58,090 actually specifying the format of my string value OK person s. 33 00:01:58,230 --> 00:02:01,680 So this person is talking is actually referring to this gets named argument. 34 00:02:01,710 --> 00:02:02,380 OK. 35 00:02:02,640 --> 00:02:08,070 And here I have a person and this is actually a newline character space per cent. 36 00:02:08,110 --> 00:02:15,850 It's again this token here dispersant S is actually for this screen Meffert OK and person. 37 00:02:15,840 --> 00:02:18,980 And this is actually a newline character space. 38 00:02:19,200 --> 00:02:24,730 And I have a person here that is actually referring to this keyboard Meffert here. 39 00:02:24,810 --> 00:02:25,550 OK. 40 00:02:26,040 --> 00:02:27,900 So hopefully that makes sense. 41 00:02:27,900 --> 00:02:30,920 And now let's actually create an abstract method. 42 00:02:30,960 --> 00:02:37,080 So as you can see here I actually created this abstract method here and I notice that I actually didn't 43 00:02:37,610 --> 00:02:44,970 are actually putting curly braces after this MF at name in order to put in our own implementations because 44 00:02:45,030 --> 00:02:49,520 abstract methods cannot be actually cannot have body. 45 00:02:49,670 --> 00:02:54,960 OK so if we're actually putting in curly braces here as you can see it's non-chain as an error and it 46 00:02:54,960 --> 00:02:58,340 says that abstract methods can not have a body. 47 00:02:58,430 --> 00:03:03,560 OK so we cannot actually create a body for this abstract Meffert. 48 00:03:03,780 --> 00:03:06,690 And the access modifier of this method is public. 49 00:03:06,900 --> 00:03:12,690 And as you can see it is if it is actually abstract the return type of this Meffert is double and the 50 00:03:12,690 --> 00:03:16,040 name of this method is evaluates per performance. 51 00:03:16,050 --> 00:03:16,750 OK. 52 00:03:17,130 --> 00:03:19,770 And this method actually is an abstract method. 53 00:03:19,950 --> 00:03:28,320 And the other classes that actually inherit from the computer class need to actually create a body for 54 00:03:28,320 --> 00:03:29,100 this method. 55 00:03:29,230 --> 00:03:29,920 OK. 56 00:03:30,160 --> 00:03:36,750 Otherwise with what those classes of would wind up with actually a compilation error and I'll show you 57 00:03:36,780 --> 00:03:40,020 in a second how you can actually use this method. 58 00:03:40,360 --> 00:03:46,250 But because I told you that a computer by itself is actually an abstract concept. 59 00:03:46,290 --> 00:03:47,430 OK. 60 00:03:47,760 --> 00:03:51,610 We declared this class as as an abstract class. 61 00:03:51,630 --> 00:03:52,190 OK. 62 00:03:52,410 --> 00:03:56,960 And this class has actually an abstract method evaluates performance. 63 00:03:57,090 --> 00:04:03,620 If I ask you to evaluate the performance of computer you may ask me that what kind of computer are this 64 00:04:03,870 --> 00:04:08,820 computer or laptop computer or a smart phone computer or a tablet computer. 65 00:04:08,940 --> 00:04:11,800 So this Meffert is actually an abstract benefit. 66 00:04:11,880 --> 00:04:12,420 OK. 67 00:04:12,630 --> 00:04:20,160 And the other classes that are actually called concrete classes such as this thub computer laptop laptop 68 00:04:20,160 --> 00:04:25,920 computer as you can see smartphone computer tablet computer These glasses are concretes glasses. 69 00:04:25,920 --> 00:04:26,430 OK. 70 00:04:26,700 --> 00:04:34,430 And if these glasses actually extend from this computer class as you can see they need to actually they 71 00:04:34,450 --> 00:04:40,530 need to actually create a body for the Smurfit they need to actually override this Meffert and create 72 00:04:40,620 --> 00:04:47,400 a body for this effect and specify what's the evaluate what's the actually performance or how how they 73 00:04:47,400 --> 00:04:51,900 can actually evaluate the performance of two of those specific computers. 74 00:04:51,900 --> 00:04:52,950 OK. 75 00:04:53,340 --> 00:04:55,240 So hopefully that makes sense. 76 00:04:55,260 --> 00:05:00,380 And remember that you cannot create an object from an abstract class OK. 77 00:05:00,440 --> 00:05:06,550 So let's actually go back go inside that inside of this top computer that have a fight here and now 78 00:05:06,800 --> 00:05:17,240 let's actually after the class name just typing here extends OK Computer and now it is now showing us 79 00:05:17,300 --> 00:05:17,960 an error. 80 00:05:18,020 --> 00:05:18,680 OK. 81 00:05:18,950 --> 00:05:23,690 And let's actually hover our mouse pointer over the whole area and see what happens. 82 00:05:23,690 --> 00:05:27,980 Class desktop computer must either be declared up. 83 00:05:28,010 --> 00:05:35,920 Abstract OK or implied or implement abstract method evaluates performance in computer. 84 00:05:36,020 --> 00:05:36,570 OK. 85 00:05:36,990 --> 00:05:46,160 So because you are actually saying that this computer extends computer we either need to actually declare 86 00:05:46,160 --> 00:05:54,430 this class as an abstract class or we must actually override the abstract Meffert that is actually inside 87 00:05:54,760 --> 00:05:57,310 of there are actually computer class. 88 00:05:57,320 --> 00:06:00,170 OK so that is actually putting some lines of code. 89 00:06:00,200 --> 00:06:03,410 And then I explain to you what's going on here. 90 00:06:03,470 --> 00:06:10,480 So first of all let's actually do declare some instance variables here inside of this stop computer. 91 00:06:10,820 --> 00:06:16,790 And as you can see here every desktop computer has a mouse every desktop computer has a super power 92 00:06:17,150 --> 00:06:20,220 and every desktop computer has a ram key. 93 00:06:20,420 --> 00:06:25,270 And as you can see here in my first instance variable is a private stream mouse. 94 00:06:25,490 --> 00:06:29,290 My second instance variable is private double Sibiu power. 95 00:06:29,480 --> 00:06:33,400 And my first instance variable is private double RAM. 96 00:06:33,520 --> 00:06:39,710 OK so now let's actually create a constructor for this desktop computer class. 97 00:06:39,710 --> 00:06:42,570 So here I'm going to actually pasting this constructor here. 98 00:06:42,710 --> 00:06:43,150 OK. 99 00:06:43,250 --> 00:06:49,670 And as you can see this is my constructor for this this computer class and the access modifier of this 100 00:06:49,670 --> 00:06:51,320 constructor is public. 101 00:06:51,440 --> 00:06:54,860 The name of this constructor is desktop computer. 102 00:06:54,860 --> 00:06:57,550 And this construct that actually accepts some arguments. 103 00:06:57,560 --> 00:06:58,070 OK. 104 00:06:58,310 --> 00:07:01,900 And the first argument as against is of type String name. 105 00:07:01,910 --> 00:07:07,910 The second argument against is of types 3 inch screen and the first argument as against C is again of 106 00:07:07,910 --> 00:07:09,630 type String keyboard. 107 00:07:09,710 --> 00:07:16,970 And here this fourth argument is of type String mouse here as you can see this fefe argument is actually 108 00:07:16,970 --> 00:07:19,920 of type double Sibiu CPO power. 109 00:07:20,210 --> 00:07:26,170 And here these six are argument as you can see is after double and the name of this argument is that 110 00:07:26,180 --> 00:07:31,820 I'm so here because we are actually inheriting all of the features and behaviors that are actually inside 111 00:07:31,820 --> 00:07:33,290 of this computer class. 112 00:07:33,290 --> 00:07:37,730 We need to initialize the constructor of the superclass. 113 00:07:37,730 --> 00:07:43,100 So as you can see inside of this computer class we have this constructor here and inside of this desktop 114 00:07:43,100 --> 00:07:50,950 computer I need to initialize the constructor of the superclass by just typing super name screen keyboard. 115 00:07:50,970 --> 00:07:56,270 OK as you can see this computer class as you can see this construct it actually accepts free arguments 116 00:07:56,600 --> 00:08:01,810 name screen keyboard and inside of this desktop computer. 117 00:08:02,510 --> 00:08:05,080 As you can see here these are super. 118 00:08:05,080 --> 00:08:09,400 He actually accepts free arguments name screen keyboard. 119 00:08:09,410 --> 00:08:10,150 OK. 120 00:08:10,530 --> 00:08:17,870 Now and here as you can see I am actually instantiating at my instance variables that I actually declared 121 00:08:17,930 --> 00:08:21,920 in this class the start mouse assignments operator mouse. 122 00:08:22,010 --> 00:08:27,320 Ok this that C-p a power assignment operator CPQ power. 123 00:08:27,430 --> 00:08:30,500 Does that RAM assignment operator. 124 00:08:30,650 --> 00:08:36,830 OK so now I'm going to actually pasting some lines of code here and then I'm going to actually explain 125 00:08:36,830 --> 00:08:38,420 to you what's going on here. 126 00:08:38,420 --> 00:08:39,100 OK. 127 00:08:39,740 --> 00:08:45,060 So as you can see here first of all I actually pasted this line of code here this method. 128 00:08:45,080 --> 00:08:45,660 OK. 129 00:08:46,040 --> 00:08:49,190 And the Axis modifier of this method is public. 130 00:08:49,190 --> 00:08:52,290 The return type of this method is three gets mouse. 131 00:08:52,310 --> 00:08:57,130 OK this is actually to get here for this mouse instance variable. 132 00:08:57,200 --> 00:08:58,170 OK. 133 00:08:58,340 --> 00:09:03,050 And here I actually created a set here for this mouse instance variable. 134 00:09:03,140 --> 00:09:04,800 Ok public it says mouse. 135 00:09:04,850 --> 00:09:05,500 OK. 136 00:09:05,930 --> 00:09:14,390 And then I actually created a getter for a super power instance variable gets you power. 137 00:09:14,660 --> 00:09:19,700 And then I created a setter for the spew power instance variable. 138 00:09:19,730 --> 00:09:26,450 And as you can see here inside of the Smurfette I actually created an if statement if the value of this 139 00:09:26,540 --> 00:09:27,040 argument. 140 00:09:27,050 --> 00:09:33,980 Ok so your power is less than or equal to number 0 then fro new legal argument exception. 141 00:09:34,080 --> 00:09:36,500 So if Sibiu power must be greater than zero. 142 00:09:36,500 --> 00:09:37,100 OK. 143 00:09:37,160 --> 00:09:43,980 And then here I am actually assigning the value of this argument to this spew power instance valuable 144 00:09:44,660 --> 00:09:52,370 and that I created a guitar for this Ahram instance variable and here I created a set here for this 145 00:09:52,590 --> 00:09:53,990 of an instance variable. 146 00:09:53,990 --> 00:10:01,420 And as you can see here inside of the setter I actually created an if statement if the value of this 147 00:10:01,680 --> 00:10:09,500 instance value bet is less than or equal to number zero then fro new illegal X argument exception RAM 148 00:10:09,680 --> 00:10:11,910 must be greater than number zero. 149 00:10:12,080 --> 00:10:18,790 And then here I am assigning the value of this argument to this instance variable does that from an 150 00:10:18,880 --> 00:10:20,430 assignment operator. 151 00:10:20,550 --> 00:10:20,890 OK.