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Hello everyone.



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So in the last video we started discussing about whoops we learned what is whoops.



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Object Oriented Programming Baghdad object and how we can create glasses.



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So in this video we will see how to create objects and how to access its properties so in the last video



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we created this class.



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And we know how to create glasses.



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So now let's see how to create object of this class



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so when we write so when we write in a is the name of the variable and a is of type in digit.



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Now we have a class student



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this student has two properties age and William.



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But now I want to create object S1.



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Now I want to create a student or I can say I want to create a variable S1 of type student.



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How can we say that because glasses nothing but a user defined data type



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that another name of glasses user defined data type for example and double floored.



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These all are built into the types building types whereas class is a user defined data type okay.



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So when we write in a is the name of the variable but when we write student S1 S1 is the name of the



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object here.



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We will call it a variable.



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And here we will call it the object a is of type in digit S1 is of type student.



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Okay.



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So a student.



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Class glasses nothing but the user defined data type.



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So let's see when we write in into what will happen we will get four blocks of memory space and the



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name of this block is a.



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Okay.



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And there will be random values random garbage value so when we write student S1 we will get a memory



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block the name of this block is S1 and virtual boot size so student contain two integers.



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Rule number and age both our 44 bytes.



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So in total eight bytes so the size of this block will be approximately eight bytes not exactly.



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It byte because there are many other things also we do not need to understand them yet.



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Okay so this is nearly eight bytes approximately eight bytes but not exactly it bytes.



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So S1 will contain H and it will have rule number and garbage values.



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Okay.



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Similarly when we write in day there was garbage values.



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So similarly when we create an object there will be garbage values.



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Similarly we can create an understood end student as to again we will get approximately eight bites



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of memory space name is as to age and a number.



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And similarly garbage value Okay so till now we have created objects statically below we are creating



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objects strategically but we can also create objects dynamically



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so in the static how we create objects practically in.



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Okay.



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Student S1 student S2



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So what will happen.



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Like student s when is it s containing age and rule number garbage values so why garbage values.



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Because we are not setting the properties ourself below that's why garbage values.



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Similarly for Sudan to age rule number garbage values



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Okay now let's see how we can create objects dynamically so for creating an integer dynamically the



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same indexes into start a new and



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the.



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So this is this index for creating an integer.



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Benny Michaeli.



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So what will happen in the heap memory we will get for bytes of memory space and in the static memory.



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This is the name of the variable e and efforts.



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This is handed down and it will be here.



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Okay so this is static memory



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and this one is he similarly if we want to create an object dynamically the syntax will be similar to



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this one we will write student



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then start as t is new keyword and then the data type which is student So what will happen in the heap



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memory.



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We will get nearly eight bytes and this will have each rule number garbage value and in the state in



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the static memory we will get eight bytes of memory space because as TS a point.



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Similarly the size of A's eared bytes because it's a pointer and let's say for there this is 300.



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So this will contain 300.



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Okay this will contently entered



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okay.



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So what we used to do with the variables we can also do with objects.



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Now let's sing called



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so let's create object statically



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so we can create many object student as to similarly we can create many objects in one line like we



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used to do with variables so as tree as food as 5 and so on.



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Now let's create object dynamically so creating objects dynamically



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so this index is quite similar.



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So student start as six as new keyword and then later type which is student



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now let's see how we can set the property of an object.



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Okay so we have an object S1 S1 contain H.



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And rule number



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and garbage of ideas.



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Similarly we have object as to age rule number garbage value.



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And let's take one dynamic object.



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So this is s.t..



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Now this is our heat memory and here we have each and William but which contain garbage values.



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Okay so when we write and a word will happen we will get four bytes of memory space.



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Now if we want to put something inside this box what we will do we will write a equals five so five



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will come here.



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Now similarly if I want to write something here what I can do is one equals.



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24 now is it right or wrong it is wrong because S1 one contain multiple properties if I want to set



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each this index will be as one dot each equals 24.



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Now this is right.



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So 24 will come here.



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This value will become 24.



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Similarly I can central number s one dot rule number is let's say a hundred.



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So this value will become a hundred.



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Okay so syntax is very simple so what we have to right this is object name dot property name.



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Okay.



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Object name dot property name.



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Now let's see in code



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as one dot age let's say 24 S1 DOT rule number let's say a hundred and similarly we can also print c



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out as rendered age



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C out as one dot.



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Rule number.



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Okay so this is a very simple index to access the properties of an object.



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Now let us talk about how to access properties of our dynamically created object.



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So we have object S6 which is dynamically created sorry.



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Wait a second



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so if we have an integer variable which is dynamically created.



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So what will be the situation and star.



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A is new and so this is it bytes pointer and this is our 4 bytes memory space so we cannot write simply



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equals 5.



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This is wrong.



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The right way to do is first we have to reach in this box now for reaching this box.



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We will use R to start R D defense operator.



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So start is five now five will come here.



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Similarly in case of dynamic created object we will do something similar to this.



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So we have object S6 which is dynamically created.



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So S6 is new student Okay so this is a pointer of eight bytes and now this box contain H and lumber



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which are garbage initially.



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Okay so we cannot write a six dot age.



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This is wrong.



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What it will do is it will go to a six and inside a six.



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It will try to find each but it is present in this box.



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Age is present in this box.



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So we have to reach this box for it in this box.



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We will use data fence operator.



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So start S6 by doing statistics.



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We have reached this at this box dot age let's say 5 now 5 will come here.



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Similarly star as 6 Dato number let's add 200 so two hundred will come here.



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Okay so in case of four dynamically created objects we have to use data fence operator to reach this



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box okay so let's good



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we have to use star operator so start A6



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last age twenty three



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is six Natali numbers



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let's say 30 okay.



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Now this is.



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Now we have all.



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Now we also have a shortcut to do this.



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We will write a six and a each is 23 A6 and orderly number is 30.



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Okay so these two lines and these two lines that exactly seem uh exactly same means uh if we will right



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start Essex dot age and we will write a six note age ethics arrow age.



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So these two are exactly same



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this arrow is a shortcut.



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Okay this is a shortcut they will exactly Wuxi.



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But this is a shortcut.



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Many people use it.



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Instead of using stored and then dart and then brackets and all that stuff it is much simpler to use



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ETL okay.



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Now



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if we will run this file we will get a lot of errors.



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Let's see why



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okay.



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So I am telling you if we will run this file we will get a lot of errors.



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So let's see so we are getting a completion edit and let's see that ID.



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So this is dated ages private roll number is private.



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Age is private.



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Again age is private.



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So we are getting something.



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So we are getting an error which is telling us that age.



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Roland but these are private.



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Now let's see what is private.



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So there is a concept in Opes called access modifiers excess modifiers so excess modifiers is who all



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can access the properties and functions of a class.



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Okay.



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So there are two types of excess modifier public private and the third one is predicted



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so we will not discuss about protected yet.



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We will discuss about public and private.



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So what private uses private will say you can access properties of a class inside the class only.



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Okay.



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So I would say as you can access the properties only inside the class what we are doing here is C H.



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Andrew Lambert can only be accessed within student class letters is between this bracket and this record



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private will say this to fields.



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Rule number and age can only be accessed within the student class that is between this bracket and this



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bracket.



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Okay



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what public says is if the access modified is public then you can use the properties of the class anywhere



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anywhere in your program.



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You can use the properties of the class.



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Whereas if the access modified is private you can use the properties inside the class only.



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So here we are when we created these two variables these two properties we have not defined any access



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modifier so by default the access modifier is private.



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Okay so default access modifier is private if you will not specify the access modify it.



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Default will be private.



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So here rule number n h by default they are private.



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And what I'm doing here is C I am using excess I am using each and lumber outside the class in the main



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function I am using each and number.



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That's why we are getting a compilation error which is saying that rule number n h are private and you



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cannot use them outside the class.



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Similarly we are using a general number here.



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Okay.



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So what we have to do if we will if I want to use the properties of the class outside the class we have



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to make them public.



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So for public work we will do.



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There is a very simple index.



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We just have to write the keyword public so we will use.



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We will write the keyword public and then column.



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So after writing public column what will happen



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so after writing public everything everything below public will become public.



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So now rule number and age they are public and now this line is correct this line is correct.



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Basically we will not get any uh any compulsion at it.



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Okay.



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Now let's see how come by lament program so we are getting ahead.



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So what is the idea.



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Okay.



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This Beckett it's right now



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see how program is running



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okay.



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Now what if



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I make in Deja each private.



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So private.



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Now what will happen now



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so when you write public everything inside public will become public.



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So this rule number is public.



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But now we have defined and another access modifier which is private.



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So now age is private.



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So it can only be used between this and this blanket that is each can only be used inside.



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Class and the but can be used any weird



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so as one dot age is 24.



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This line is correct because.



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Sorry.



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This line is wrong because age is private but this line is correct.



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Why.



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Because it is public.



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Rule number is public.



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Age is private.



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So we will get compilation error wherever we have used each and outside the class.



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Let's come bilateral program.



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Now this time if you will see that ad that it will be only due to age ages private ages private ages



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private there will be no added regarding the roll number.



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Okay.



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So this way we can use like we can define multiple access modifiers.



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Okay.



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Now I want to show you one more thing.



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Let's remove this called okay.



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Uh let's remove everything else



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okay.



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So what I did it is I uh I'm creating a lot I care to file student do you start CPB.



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And this is I want all the class which is containing the class only.



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Now why I am doing this is



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see these are concept in software development which is called isolation of logic so overt isolation



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of logic seizes whenever you want to create a class create a class in a separate file.



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So we will have a file.



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Now this file will create the class and we will have another file in this file.



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We will use this class use class here okay.



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So it's like best practice in the software in the software industry.



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Because the logic is different.



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Here we are here we will just define the class.



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And here we will use class.



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So I did exactly the same.



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Okay.



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So I have a class which is student and I have entered the class and I have another file student.



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You start TPB here.



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We are using the student class.



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Now if I will run this program it will to me and added model with data.



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It will say I don't know what is student why.



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Because student is defined in a separate file.



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So if I want to use student in this file right what I have to use I have to include that file in this



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in this current file.



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So hashing glued downloaded commas name of the file student art CPB okay.



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Now this is correct.



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Now let's start.



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Now let's turn our program



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okay.



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So this is training me at it.



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Uh what is the error.



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Let me see.



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And funds in danger.



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Private.



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Oh I have to run this class also.



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Now this.



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Now this will be correct see it is running now.



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Okay.



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So always this is a good practice.



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Make glass and separate file and use data class in your current file.



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Now.



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Now when we included I use gym class I used this ad was for I use string but then I used but when I



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included student file I used the downloaded data commas because for Ford built in files the files which



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are already present we have to use these arrows.



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But if we create a fly file on our own that is user file the file that we have created we have to use



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devil records.



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Okay.



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This is just a syntax.



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Nothing else.



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Okay.



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So thank you.