1 00:00:00,930 --> 00:00:06,300 Well discussing your neighbors B-ble if you discuss tactic with him as a no let alone little bit more 2 00:00:06,300 --> 00:00:07,400 about them. 3 00:00:07,680 --> 00:00:12,900 We not only shut them all very relaxed and our student class to incorporate static variables. 4 00:00:14,590 --> 00:00:20,510 Like startlement that's to clear the books are also declared with the key word stocktake and it means 5 00:00:20,510 --> 00:00:28,890 that there's a topic to the class that is there independent of any instances of the class like Instance 6 00:00:28,890 --> 00:00:35,340 variables static variables are also declared directly with the necklace that is a class level. 7 00:00:35,340 --> 00:00:40,290 So you can declare them and methods and you will get compiler dollars if you declare them and Mather's 8 00:00:42,230 --> 00:00:46,370 also like Instance variables they get initialized with a default value. 9 00:00:46,430 --> 00:00:54,090 If they are not explicitly initialised not the static variable is declared with a public access modifier 10 00:00:54,480 --> 00:00:57,810 then any code that is external to the class can access it. 11 00:00:57,810 --> 00:01:03,870 We are that class in of course code inside the class can access it directly. 12 00:01:03,870 --> 00:01:09,180 Also if it has default access level we know that only classes within the same package can access that 13 00:01:09,180 --> 00:01:16,460 variable so just ecstatic my first class name followed by dot operator is used to access and this topic 14 00:01:16,460 --> 00:01:23,930 really was declared in that class since I think we're able to start a class they're also referred to 15 00:01:23,930 --> 00:01:25,530 as class variables. 16 00:01:26,590 --> 00:01:29,100 So there is only one copy of a static variable. 17 00:01:29,160 --> 00:01:38,020 But class that copy is shared across all objects of the class what this means is if one object updates 18 00:01:38,030 --> 00:01:43,610 the value of a static variable then all other objects will see the same object value. 19 00:01:44,360 --> 00:01:51,040 On the other hand with Instance variables we know that every object of the class gets its own copy of 20 00:01:51,130 --> 00:01:57,390 every instance variable declared in the class so instance variables hold values unique to each object 21 00:01:57,840 --> 00:02:00,020 but does nothing but the spirit of the object. 22 00:02:01,620 --> 00:02:07,290 Here's a simple example here we have the Student class with the static variable called Con which is 23 00:02:07,290 --> 00:02:08,740 initialized to zero. 24 00:02:09,240 --> 00:02:13,940 There are also three instances of the Student class named S1 S2 S3. 25 00:02:14,040 --> 00:02:21,730 So as one increments can then count will be 1 and 2 and 3 will see the same or better value 1. 26 00:02:21,740 --> 00:02:28,480 Now if S2 increments can then convert increment or to do an as one industry will also see the contract 27 00:02:28,500 --> 00:02:35,930 us to not count is declared with public modifier then any court extended to the Student class can also 28 00:02:35,930 --> 00:02:42,680 include incremented and that a better value will once again be visible to any court that is able to 29 00:02:42,680 --> 00:02:47,990 access the and variable so static variable values are truly global. 30 00:02:48,180 --> 00:02:55,470 That is there is only one copy of the static variable per class not come into accessibility of static 31 00:02:55,470 --> 00:03:00,910 variables within the class in which they are declared they're accessible from static method to defining 32 00:03:00,930 --> 00:03:07,300 the class as both of them are started with a class but since they're also shared across objects of the 33 00:03:07,300 --> 00:03:13,440 class they are also accessible from instance methods as well as concepts of the class. 34 00:03:15,200 --> 00:03:20,390 Although we discussed accessibility of instance and static variables from the different kinds of methods 35 00:03:20,690 --> 00:03:24,650 like static on instance then must all be some confusion. 36 00:03:24,670 --> 00:03:26,140 So to be 100 percent sure. 37 00:03:26,180 --> 00:03:32,260 Let's look at this example had the class to start degradable and one instance variable. 38 00:03:32,340 --> 00:03:38,760 We also have two methods one instance method and one static method an instance mother can access anything 39 00:03:38,820 --> 00:03:41,400 that is topic for instance. 40 00:03:41,430 --> 00:03:47,310 So as you can see the instance method can access the instance really the static variable and also the 41 00:03:47,310 --> 00:03:48,910 static method. 42 00:03:48,930 --> 00:03:54,970 So basically there is no restriction when it comes to instance methods nobody comes to a static method 43 00:03:55,300 --> 00:04:01,620 we know that it needs to stay away from anything to do with objects that so as you can see it can access 44 00:04:01,620 --> 00:04:08,310 the static variable as it is not object specific but we get a compiler error when it Kreiss to access 45 00:04:08,550 --> 00:04:15,860 either the instance variable or the instance method as their object specific however the final statement 46 00:04:15,860 --> 00:04:22,430 shows that it can access an instance method or even an instance variable enough object to that object 47 00:04:22,430 --> 00:04:25,550 reference that is perfectly fine. 48 00:04:25,550 --> 00:04:31,810 Like we see here the object can be an object of the same class in a static matter it is different. 49 00:04:32,930 --> 00:04:38,690 It is just that the static method cannot directly access any data related stuff declared in the scene 50 00:04:38,690 --> 00:04:46,250 class let's make a small enhancement below a student class example to this topic really both in action 51 00:04:47,150 --> 00:04:54,260 you can also find the biggest quote in the resources section let's in enhance our student example a 52 00:04:54,260 --> 00:04:55,480 bit more. 53 00:04:55,490 --> 00:05:00,220 Let's say we want to keep track of the number of student objects getting created. 54 00:05:00,710 --> 00:05:06,050 So there should be a counter which gets incremented every time a student object is created. 55 00:05:06,950 --> 00:05:10,590 Begin create the counter as a static variable. 56 00:05:10,640 --> 00:05:13,640 So let's create a static variable call student called 57 00:05:16,410 --> 00:05:29,020 Write topic and that's just naming does student count and let the default be zero and here in the constructor 58 00:05:29,790 --> 00:05:39,050 let's just say student called less bliss unlist just hard to get there for the student called 59 00:05:42,430 --> 00:05:43,370 does get student 60 00:05:46,610 --> 00:05:48,190 can actually make it static 61 00:05:54,190 --> 00:05:59,410 and let's just go into the Student class method and let's say 62 00:06:02,400 --> 00:06:14,720 number of students created so far and you can simply do this to that class name and get student 63 00:06:17,350 --> 00:06:24,960 which is a static method static methods can be worked directly with the class name. 64 00:06:25,050 --> 00:06:27,420 We already know that said. 65 00:06:27,840 --> 00:06:38,810 So let's just go ahead and compain her on it and it says number of students created so far is three 66 00:06:40,180 --> 00:06:49,990 and that's said Now can you guess what happens if it if we remove the static keyword Yes and also make 67 00:06:49,990 --> 00:06:51,500 this this. 68 00:06:51,790 --> 00:06:54,450 In this case it's an instance variable. 69 00:06:54,460 --> 00:06:56,680 So it is specific to the object. 70 00:06:57,010 --> 00:07:04,570 And when we increment it for each student object it just gets incremented from 0 to 1 and that's about 71 00:07:04,570 --> 00:07:04,930 it. 72 00:07:05,080 --> 00:07:11,230 So it is incorrect right so it's not going to keep track of the total number of students that are getting 73 00:07:11,230 --> 00:07:12,240 created. 74 00:07:12,670 --> 00:07:17,210 So it just keeps on incrementing from 0 to 1 and that's incorrect. 75 00:07:17,350 --> 00:07:24,850 So it has to be static and it's true we started and that's about it.