1 00:00:00,450 --> 00:00:05,940 Hire everyone in this theater all I'm going to touch about constructors in Java. 2 00:00:05,970 --> 00:00:13,430 So first when need to create a job or project find new click on Java project and for the project name 3 00:00:13,530 --> 00:00:22,930 just type in here constructors in Java and click on finish. 4 00:00:23,270 --> 00:00:27,800 So as you can see here our Java project is now created. 5 00:00:27,830 --> 00:00:31,550 So now we need a main class for our project. 6 00:00:31,550 --> 00:00:39,770 So just click on this as our See folder here and then click on File New and then click on class. 7 00:00:39,800 --> 00:00:46,950 So for the class name just type in here Main and for the package name we need our reverse domain here. 8 00:00:47,090 --> 00:00:53,000 So just type in here com that your name dot project name constructor's 9 00:00:56,960 --> 00:00:57,470 in Java 10 00:01:00,430 --> 00:01:01,110 OK. 11 00:01:02,630 --> 00:01:08,930 And for the modifiers choose public and here make sure that you check this check box here that says 12 00:01:09,200 --> 00:01:13,240 public static void main method and then click on finish. 13 00:01:13,340 --> 00:01:17,020 So as you can see here our main class is now created. 14 00:01:17,180 --> 00:01:21,620 So now let me actually delete this comment here and then. 15 00:01:21,620 --> 00:01:24,930 Now I want to actually create Tigard objects. 16 00:01:25,190 --> 00:01:32,180 So in order to create a target object I need a class called Tiger in order to actually show me how I 17 00:01:32,180 --> 00:01:35,100 can actually create Piute objects. 18 00:01:35,120 --> 00:01:44,090 So just click on this package here and then click on File New and then click on class OK. 19 00:01:44,520 --> 00:01:47,600 And for the class name just type in here Tiger. 20 00:01:48,210 --> 00:01:52,950 And as you can see it's going to actually put this class inside of this package. 21 00:01:52,950 --> 00:01:58,450 OK and for the modifiers choose publish and click and finish. 22 00:01:58,770 --> 00:02:02,710 So as you can see here are Tiger class is now created. 23 00:02:02,730 --> 00:02:09,920 So now I want to actually specify the characteristics and the behaviors of my tinier objects. 24 00:02:10,170 --> 00:02:13,160 I to actually create some instance variables here. 25 00:02:13,500 --> 00:02:21,900 So that data type of my instance variable is in it and the name of my instance variable is speed. 26 00:02:22,470 --> 00:02:29,130 And then I assign a value to my variable and make sure that you actually put the private access modifier 27 00:02:29,850 --> 00:02:32,020 for your instance variables. 28 00:02:32,040 --> 00:02:32,700 OK. 29 00:02:33,060 --> 00:02:38,520 And here I want to actually create a get here and also turn my head for this instance value. 30 00:02:38,580 --> 00:02:42,870 OK so the access modifier of my get RMF it is public. 31 00:02:43,860 --> 00:02:50,800 And the return type of My guess is in the name of my guess is get speed. 32 00:02:51,260 --> 00:02:52,000 OK. 33 00:02:52,290 --> 00:02:57,380 And then I need to put in a pair of round brackets after my name. 34 00:02:57,510 --> 00:03:01,870 And then I need to open and close my Meffert by using these curly braces. 35 00:03:01,950 --> 00:03:06,010 And then I return the value of this instance variable. 36 00:03:06,180 --> 00:03:09,730 So here I want to create a set here for my instance variable. 37 00:03:09,780 --> 00:03:14,150 You can actually create only a get here for your instance variables. 38 00:03:14,160 --> 00:03:19,920 If you don't want to allow any other classes to change the value of your instance variables. 39 00:03:19,920 --> 00:03:20,600 OK. 40 00:03:20,760 --> 00:03:26,460 For example inside the main class if you want to actually create an object from the Tile class I just 41 00:03:26,460 --> 00:03:36,170 need to type in here Tiger and the name of my object is my tiger I put in an assignment operator here 42 00:03:36,710 --> 00:03:38,560 and there I use this key word here. 43 00:03:38,600 --> 00:03:45,970 New and then again I refer to the name of my class and then I put in a pair of round brackets after 44 00:03:45,970 --> 00:03:47,640 my classmate. 45 00:03:47,680 --> 00:03:48,290 OK. 46 00:03:48,700 --> 00:03:52,280 And then I need to put in a semicolon at the end of my statement. 47 00:03:52,330 --> 00:03:59,610 So now I can actually access the value of my speed instance variable and then output that value to to 48 00:03:59,710 --> 00:04:02,040 the console by using this term. 49 00:04:02,080 --> 00:04:05,260 OK so here I can just type in here. 50 00:04:05,260 --> 00:04:09,670 System that out that princeling. 51 00:04:09,700 --> 00:04:15,760 And then inside the prentices I just need to refer to the name of my object my tiger that gets speed 52 00:04:16,870 --> 00:04:20,530 and then I need to put in a semi-colon at the end of my statement. 53 00:04:20,710 --> 00:04:27,960 So now if I run on my project as you can see this value is the value of this speed instance variable. 54 00:04:27,960 --> 00:04:28,690 OK. 55 00:04:29,020 --> 00:04:36,160 And as you can see I didn't create a search term I felt for my speed instance variable and I can only 56 00:04:36,220 --> 00:04:41,010 access that value in my main class inside the main if all. 57 00:04:41,120 --> 00:04:47,190 I can not change the value of my speed instance value but of does my target object. 58 00:04:47,230 --> 00:04:47,610 OK. 59 00:04:47,620 --> 00:04:52,960 So here I want to actually create a set term I felt for this split instance variable. 60 00:04:53,080 --> 00:04:58,240 So the access modifier of this instance variable is public. 61 00:04:58,240 --> 00:05:01,210 The return type of this method is void. 62 00:05:01,210 --> 00:05:04,120 This means that disbenefit is going to return nothing. 63 00:05:04,630 --> 00:05:11,780 And the name of this method is set speed and that I need to put in a around brackets after my Meffert 64 00:05:11,800 --> 00:05:12,540 name. 65 00:05:12,550 --> 00:05:16,450 And then I want to specify that this method is going to accept an argument. 66 00:05:16,510 --> 00:05:17,090 OK. 67 00:05:17,350 --> 00:05:27,010 So the data type of part of my argument is 8 and the name and the name of my argument is value and then 68 00:05:27,010 --> 00:05:30,890 I need to open and close my method by using these curly braces. 69 00:05:31,030 --> 00:05:37,360 And then I refer to the name of my speed instance variable and then I put in an assignment operator 70 00:05:37,360 --> 00:05:41,610 here and then I refer to the name of my argument value. 71 00:05:41,620 --> 00:05:46,130 Now I want to actually create a behavior for my Tigard objects. 72 00:05:46,210 --> 00:05:48,990 For example of my tired objects can fight. 73 00:05:49,030 --> 00:05:52,050 So the axis modifier of this method is public. 74 00:05:52,420 --> 00:05:56,960 And the return type of this if it is void the name of this method is fight. 75 00:05:57,010 --> 00:06:04,270 And then I need to actually put a pair of round brackets after my Meffert name and then I need to open 76 00:06:04,360 --> 00:06:07,200 and close my if by using these curly braces. 77 00:06:07,240 --> 00:06:15,370 So inside my head I just need to type in a system that out that princeling and that inside Apprentice's 78 00:06:15,430 --> 00:06:24,430 I can just put in two double coats and inside the double coats I can just typing it OK. 79 00:06:24,740 --> 00:06:28,440 And then I need to put in a semicolon at the end of my statement. 80 00:06:28,850 --> 00:06:34,670 And then inside the main class and inside the main method I can just refer to the name of my object 81 00:06:34,700 --> 00:06:37,700 my tiger that fight. 82 00:06:37,740 --> 00:06:42,090 And if I hit on my project as you can see disvalue is now out with it to the console. 83 00:06:42,170 --> 00:06:47,090 OK I want to actually talk about constructors in Java. 84 00:06:47,220 --> 00:06:56,170 OK so what is actually a constructor constructor is a block of code which runs when you use new keyboard 85 00:06:56,480 --> 00:06:58,690 in order to instantiate an object. 86 00:06:58,700 --> 00:06:59,240 OK. 87 00:06:59,420 --> 00:07:06,110 So as you can see here you are actually using this new keyboard in order to instantiate an object from 88 00:07:06,110 --> 00:07:07,220 this tiger class. 89 00:07:07,220 --> 00:07:07,720 OK. 90 00:07:07,730 --> 00:07:09,630 It looks like a method. 91 00:07:09,950 --> 00:07:11,810 A constructor looks like a method. 92 00:07:11,810 --> 00:07:14,090 However it is not a method. 93 00:07:14,120 --> 00:07:21,830 Methods have the return type but constructors don't have any return type how to call a constructor. 94 00:07:21,830 --> 00:07:26,550 The constructor gets called when we create an object of a class. 95 00:07:26,660 --> 00:07:27,170 OK. 96 00:07:27,350 --> 00:07:33,620 So as you can see here in this line of code in line 8 you are creating an an object from this tiger 97 00:07:33,620 --> 00:07:34,010 class. 98 00:07:34,020 --> 00:07:43,060 Ok so here we are calling the constructor actually the default constructor for our tiger class. 99 00:07:43,070 --> 00:07:49,520 Ok so here we are creating an object from the target class and we are calling the default constructor 100 00:07:49,760 --> 00:07:54,620 for our constructor constructs their values. 101 00:07:54,710 --> 00:07:58,130 For example it provides data for the object. 102 00:07:58,220 --> 00:08:01,150 That is why it is known as constructor. 103 00:08:01,190 --> 00:08:05,560 So what are the rules for creating the Java constructor. 104 00:08:05,570 --> 00:08:09,710 There are basically two rules defined for the constructor. 105 00:08:09,710 --> 00:08:15,810 One the first one is constructor name must be same as its class name. 106 00:08:15,860 --> 00:08:16,390 OK. 107 00:08:16,430 --> 00:08:21,790 And the second rule is constructor must have no explicit return type. 108 00:08:21,950 --> 00:08:28,260 OK so now inside the target class you want to create a constructor for this class. 109 00:08:28,460 --> 00:08:33,320 So the first rule is that the constructor name must be the same as its class. 110 00:08:33,430 --> 00:08:38,780 Ok so are the access modifier of my constructor is public. 111 00:08:39,290 --> 00:08:44,780 So it's better to always use the the public access modifier for your constructors because we want to 112 00:08:44,780 --> 00:08:49,300 use this constructor from outside of this target class. 113 00:08:49,310 --> 00:08:53,370 For example inside the main class I want to use this constructor OK. 114 00:08:53,690 --> 00:08:57,460 And the name of my constructor is Tiger. 115 00:08:57,470 --> 00:09:04,040 And then I need to put in a pair of round brackets after my constructor name and then I need to open 116 00:09:04,100 --> 00:09:07,660 and close my constructor by using these curly braces. 117 00:09:07,730 --> 00:09:13,300 So as you can see here this constructor doesn't have any return type so it is not a method. 118 00:09:13,340 --> 00:09:16,260 OK this is called constructor OK. 119 00:09:16,340 --> 00:09:21,860 So inside of this constructor I can actually provide data for my target objects. 120 00:09:21,960 --> 00:09:25,600 OK so what are the types of Java constructors. 121 00:09:25,610 --> 00:09:27,720 There are two types of constructors. 122 00:09:27,800 --> 00:09:31,450 The default constructor which has no argument at all. 123 00:09:31,520 --> 00:09:31,870 OK. 124 00:09:31,890 --> 00:09:34,460 Which is called no argument constructor. 125 00:09:34,610 --> 00:09:40,550 And the second type of constructor in Java is called parametrized constructor. 126 00:09:40,940 --> 00:09:49,100 OK so the Java default constructor or constructors that have no path emitter is known as the default 127 00:09:49,130 --> 00:09:49,940 constructor. 128 00:09:49,940 --> 00:09:53,240 OK so as you can see here this is our default constructor. 129 00:09:53,250 --> 00:09:57,470 OK this type of constructor is called the default constructor. 130 00:09:57,580 --> 00:09:57,920 OK.