Getting Started with OOP Step by Step Guide | GeeksforGeeks

Key Takeaways

Geeks for geeks has a challenge for you the 390 challenge choose what you want to learn in 2024 and aim to complete at least 90% of the course in the next 90 days and if you do that you get back 90% of what you paid for the course we believe you can do that now all you got to do is commit to your success commit with geeks for geeks Geeks for geeks has a challenge for you the 390 challenge choose what you want to learn in 2024 and aim to complete at least 90% of the course in the next 90 days and if you do that you get back 90% of what you paid for the course we believe you can do that now all you got to do is commit to your success commit with geeks for geeks okay so uh hi everyone uh very good evening to all of you uh please let me know if you can hear me clearly uh or not and my screen is visible okay so then we'll be starting off with the session let me just check the audio quality as wellar me clearly or not yeah I think my audio is fine everyone can give me a plus one if you can hear me clearly and I'm clearly visible to everyone as well okay so that we can start off uh hi tamur everyone please hit the like button as well uh as an acknowledgement and then we'll be starting off with the discussion so today since sart is not present so that is why what we'll be having is we'll be having a discussion on objectoriented programming why is it important for interviews and how you can prepare it okay so I'll walk you through uh all the concepts of objectoriented programming that are there like classes objects inheritance polymorphism and others so if you are as excited as I am for today's session so please uh give me a plus one for that okay and you can hit the like button also and we'll be starting within a minute after that okay so please make please ensure that you're liking hitting the like button and then we'll be starting off okay so yeah just let me open a whiteboard as well so that we can uh whatever I have to draw we can draw it easily as well okay so yeah will you implement in Java or C++ uh mostly I will keep it as a mix right uh like I I can I know in in both but uh I'll tell you what are the advantages which language you should be using if you want to do oops right so that also from interview perspective and my personal perspective Al I'll give you like which one I use basically I use Java for object oriented programming uh because there is lldd also that's there right so I'll discuss about these things but uh everyone uh can tell me if we can start right so yeah thanks a lot tamur and thanks a lot suar everyone is excited so yeah let me start off now okay so guys uh today what we are going to discuss is today we are going to discuss about objectoriented programming okay so today we are going to have a session on objectoriented programming like uh how you can get better in in object oriented programming or if you're someone who is uh planning to start with objectoriented programming then why you should uh learn object oriented programming what are the type of questions that you should cover okay and inside see firstly in object-oriented programming there is some theory part to it right there is some theory for that theory you should also see how you have to code that theory up in any of the languages that you use and then after that the advanced level objectoriented programming that is also known as objectoriented design or you can say lowlevel design is based on top of objectoriented programming only in this uh like in lld you have Concepts like solid solid principle dry kiss and then you have other things like uh designing splitwise and other applications so I'll walk you through everything like and also interview questions based on oops are there so we'll walk uh we'll walk uh throughout uh this thing that from the beginner perspective till the advanced level uh starting from oops that can be asked to a first year student till somebody who is working and who is planning to switch and how it is indirectly used in system designs as well okay basically lowlevel designs so everyone is ready uh plus one and hit the like button and let's move forward now okay so yes I hope that everyone can uh see uh this clearly all right so yeah guys uh let's get ahead now with the session okay uh right so yeah let's get ahead now and let us discuss some basic concepts so there are B basically some pillars in oops first of all what is a class right what is a class right what is a class in oops that is what we need to understand so before understanding class in objectoriented programming we need to understand that why do we basically need a class and if you must have learned about programming right so I will ask you what are data types first of all okay what is like what kind of data types are there you might tell me that int is there then Boolean is there and a lot of other data types are there like double and character and others right so primarily in data types you have two kind of data types can you tell me you have the primitive data type okay in data type what do you have you have got the primitive data type I will be teaching everything uh sir nowadays lldd is asked in interviews yes it is asked in interviews even to an sd1 you can be asked in interviews uh companies like Anan and others are asking these days okay so I'll tell everything in terms of uh implementation basis okay suppose even if I'm teaching class I'll teach you uh in terms of code and I'll teach you in a way that you uh understand like uh how it is implemented and practically in terms of code everything will be explained whatever will will be explained everything will be explained in terms of code only okay so if you have primitive data type there are two kinds of data types right there is one primitive data type and there is another one that is non- primitive data type please write plus two in the chat everyone is clear there are two types of uh data type primitive and non-primitive data type now what happens with primitive and non-primitive data type so in primitive data type you have got what you have got int then you can say that you have also got Boolean okay then you can say that you have got int bite then you uh like uh uh then you can say that you have got double and uh then you can say that you have got character as well right these are the inbuilt data types that are there agree with me everyone right now what is non-primitive data type for non-primitive data type we have a term that is uh that is it is user defined okay user defined so it is defined by the user as per the requirement okay it is defined by the user as per the requirement and why am I teaching this data type thing because I will explain what is a class and then I'll explain how that is used to implement the non-primitive data types okay so plus one in the chat if everyone is on the same page so far and then we'll proceed further guys everyone is clear so far okay everyone is in sync so far then we'll proceed uh you should be very interactive here okay we don't want it to be a monologue you should interact in the chat con constantly okay guys now moving on with this part so if you will see what is a Class A Class can be said as a blueprint right normally if you see the definition of class right so if I write uh class uh object oriented programming and then I'll search gfg okay then you will uh get uh like if you'll see introduction to oops then class is uh referred to as a user data type it consists of data members and functions which can be accessed uh and used to create an instance of the class okay object of the class so I'll explain object and all those things here if you will see what is a class right right so maybe suppose that if I want what if I want a data structure suppose that my requirement is what if I want a data structure so basically you can say class is a blueprint okay class is basically what class is a blueprint okay you can say that it is a blueprint right for example if you have to make your house right so whenever a builder has to build uh make a building or flat or something so there's always a blueprint right there's a proposal there's a draft that is there so class can be considered as a blueprint or a draft now how suppose that I have a requirement that I want a data type I want a custom data type where for every student what I want is I want to store the name of that student okay then I want to store the role number of that student and let's say I want to store the section of that student so tell me guys is there any data structure which allows me to store these three uh things is there any data structure that is there by default that allows me to store these three things differently definitely there is no data structure now is there any data structure in build that can help me to store let's say a string that is name then integer role number and section no you can write no in the chat there is no data structure as such now which can allow me to do that so since there is no data structure so I can do what using a class I can make a blueprint of this student requirement okay and then I can make objects uh of this uh class which I can use okay so I'll like these things will be clear as I keep on moving further so if you will see here right what I what I will do here is uh so far everyone is clear now you can uh just let me know guys now now if you will see if I wanted a student right so as I said I wanted a student uh so as class is basically a blueprint okay and if you wanted a student data type okay where every student for every student you want to store the name role number and section name is what data name is what name is in string okay role number is integer then section is what section you can say is character section a section B section c c and all that right so you can see here that for that I can define a blueprint that is I can define a class here right so what I can do is basically I can say that let's say I will define a class of a student okay and then here what I will do is I will Define let's say in uh role number okay that is the role number of the student would be in integer then I will Define what let's say I'll Define string name here okay and then I will Define what let's say I'll Define car section so let me just do it uh so what I will do is uh here I will Define car section here okay let's say car section here right so this is how I will Define it is that clear to everyone guys please write plus one in the chat now what will happen is this is a blueprint that we are making and also I will uh like what I will do is I will make a Constructor here what is Constructor I will tell you just uh just bear with me for a second okay then what I will do is let's say I will do in R then I am passing here let's say string na let's say and then I'm doing what let's say car SEC section okay so whatever role number I'll be passing that will be updated in the role number variable let's say role number will be R then name will be updated to whatever na I have passed okay then section would be updated to what whatever section I am passing here right now what is going to happen okay so tala chabi what does that mean I don't know okay so yeah if you will see here what I've done here is uh okay so what I've done here is uh so far I have declared a student class okay here you here I've decided that I'll be having a role number for it name section uh and like what I will do is I'll this is called a Constructor this section that I I have written okay this is basically what this is basically a Constructor that I have written okay Constructor this is Constructor now what is a Constructor Constructor is a function which has the same name as the class name so if you will see here guys so basically like if you will see here Constructor has the same name as the class name so the class name is student and here you can see that the function name is student so when the when the class name and function name are same that is known as Constructor here now what will happen is if I like this is basically a blueprint this class is what it is a blueprint print now how will I use it so I will Define I will tell you everything in terms of code also so I'll say that student and then let's say I will make a object let's say St is equal to new student okay so I'll write new student here and then after that let's say if I have to pass role number so let's say pass role number 79 uh which was my role number in my college then I'll pass the name as yes okay and then what I will do is I'll pass the section as let's say C because my section was see uh in my uh school days okay so if I'll pass this thing then what will happen the student object that is made no so in the student object in this particular student object the role number would be 79 the name will be Shoring yes and the SE section will be what C is that clear to everyone please write yes in the chat is this part clear okay so far everyone is clear okay so object is what object is basically an instance of the class right so I'll explain this you can see that basically class is what class is a blueprint okay class is a blueprint means what class is kind of a road map okay class is basically what class is kind of nothing but a road map that is there okay a road map or blueprint you can say uh or a draft you can say on which the object like on top of which the object is made okay so you can see here that if class has these data types right if I had the requirement for a student I wanted to store role number then I wanted to store name then I wanted to store section so I don't have a by default I don't have any data type for it so I can define a class I can define a blueprint and as many objects as I want I can have right so I can have student one student two and like that or I can declare AR of student okay so you can see if I will declare a student SC suppose and I'm having its name role number as 79 passing the name as yes and having the section is C then this is how this object when I will access the st. name then I'll get yes when I will access st. R number okay then I will get what then I will get the role number as 79 and when I'll access St do section then I'll get the section as C is everyone clear with this please write plus one and hit the like button guys if everyone is clear so far and then I will implement this also so that you can understand okay so if you will see here uh what is an object so it is basically a unit uh like uh it is it represents a unit it is real life identity okay class is basically what see if I will tell you uh if if I'm showing a building right if I'm showing the draft or a map of a building okay that is going to be made so is does it exist in real life no please write no class does not exist in real life if I'm showing you the draft or the paper for a if if I'm showing you the draft CFT or paper for a particular uh like building that is going to be made so it is just hypothetical it is not real life but when that building is made that building is a real life entity so similarly class is what class is basically class does not take any space okay class does not take any space class is just a blueprint whereas on the other hand the student takes a space a student or the object of the class basically that I'm saying okay St object that I have made of this student class that will take space is that clear to everyone please write yes in the chat okay after class and object please uh explain instance yeah I I I'll one by one I'll try to bifurcate everything is that clear to everyone guys so far okay that object takes a space many of times this question is asked in an interview that whether class takes space or object so class does not take space here because class is basically a blueprint okay on top of which the object is built so basically if you have a draft so that does not take actual land space but when you have a building made so when you have an object made so object does have some properties and some functions and some Behavior okay is that clear please write plus one and hit the like button guys and I'll proceed further also does that make sense to everyone okay so yeah uh everyone is clear so far right so you can see object is basically what it is uh like object is an instance of class instance means you can say it is it is made out of class only when a class is defined no memory is allocated okay this is very important when a class is defined no memory is allocated this is very important people get confused so class is what by it is it is just a road map right it is just it is just a it is just a draft it does not take any space whereas when an instance instance means what object okay so basically when an object is created out of the class then it takes memory because for storing this student object which has uh the uh role number as 79 okay and which has the name as yes and then section s c this will take memory inside uh in like this will take some memory inside your computer system system right inside your servers so that is why object takes a space whereas class is just a blueprint makes sense each object has a data of its own okay and you can manipulate that data if you want okay and it has functions also so these things are clear to everyone you can tell me guys instance of a class basically instance is nothing but object okay so you can say object is basically a real life entity you can say make sense uh guys okay so far everyone is clear instance means basically object only instance means like it's it's uh it's uh it's a real life entity object is a real life entity that is it you don't need to get confused basically you can say that uh when you are when you are having a particular like when when there is a particular entity now that is existing in real life that is an instance or an object you can say Mak sense code words others are also clear please uh tell me in the chat guys and then I'll proceed further with the code part here okay so I I'll tell you a bit of code also here so that you can understand everything clearly okay clear instance of an object where they have said instance of an object uh is there anywhere written instance of an object uh an instance of an object is an instance of class so object is basically like made out of class now so like there is nothing like instance of an object if there if it is mentioned somewhere you can tell me but I don't think that it is mentioned anywhere right so what I will do here is suppose that if I will like uh if I have opened the ID first of all and let's say I will select Java uh I'm selecting Java uh because uh like uh just not not any specific reason it's just that uh I need one language to code so either I could have coded in C++ or Java but here I'm using Java okay because I guess major majorly people use Java okay so if you see here what I will do is I'll make a student class here okay guys and then after that what I'll do is I'll have the int RO number defined here and then I'll say that I'll have string let's say s okay and then what I like sorry string name and then after that what I'll will have is I will have let's say car section here okay so SEC Tio n will be there now what I will do is uh in this I will have a student object that will be made and then let's say int R is the role number that I'm passing then uh what I'm doing is string na is the name that I'll be passing and then uh car section uh is what I'll be passing here right so whatever role number I'll be passing so role number is equal to R then what I'll say is name is equal to na okay and then what I do here is I'll say that section will be equal to what SEC that I'm that I'm passing here okay now what will happen here is inside like so this I have made as the class please write plus one in the chat is everyone clear with the student class that I have made uh guys please let me know everyone is able to I hope that everyone is able to obviously see it clearly but if everyone is clear now just let me know guys in the chat okay everyone is clear so far with the student class that I have made guys okay plus one in the chat and hit the like button also if you're understanding so far the number of people watching are more compared to the number of likes that that is something that I don't want so please uh ensure that you are uh if you're clear then you uh hit the like button as well okay makes sense guys very good now moving on if uh like once this is made right so what I will do here is if I will just uh scroll a bit down okay then what I will do is if I will just do what if I'll just do if I'll just declare a student object now okay student let's say what uh student object let's say St is equal to what uh let's say new student so this is how you can make an object of the class and here what I will pass is let's say inside the role number I'm passing 79 then in the name I'm passing y yes okay that is my name me say plus one okay uh very good thanks a lot so let's say section is what C okay my section was C uh right then after that if I use some print statements in order to print okay so s system.out do print Ln if I will do here okay and then what I will do is I'll let's say do what I'll do St do R number okay so first of all let's say I'll try to print the role number and then what I will do is I'll also do system.out do uh uh print Ln okay then what I will do is St do uh name uh so I'll print the name here then after that what I'll do is I'll have system.out do uh print LM then what I'll print is st. section here okay now once that is done here right so let's uh escape and let me just decrease the font here okay so what I've done is I have initialized this thing now if you if you will see if I'll run this code and you will see that role number name and section will be displayed here okay you can see clearly that the role number was 79 the name has been displayed and and the uh this thing has also been displayed c section oops start shalu you should start oops when uh like when you are in your first or second year only because that is the best time yeah I'll start like I'll keep on continuing right just after the basic yeah so if you see here uh like let's say if I have had to declare another student s two kinds of Constructors also so you can see here that whatever value I am passing okay that that like that I can pass like this when I'm making the object of the class this is the step when I'm making the object of the class and that is when this Constructor is called but this is like basically when I have made a Constructor like this now guys so basically this kind of Constructor that I have made okay it is uh uh it is known as what it is known as uh diff parameterized Constructor okay because I'm passing parameter here okay please write p in the chat uh is everyone clear this kind of uh way in which we initialize the object is known as parameterized Constructor so when we make a Constructor like this and when we like when we make an object like this where we pass uh parameters right so where we have passed role number and then name and section so this when this kind of Constructor is called it is this Constructor is known as parameterized Constructor is that clear please write plus one in the chat guys is everyone able to hear me okay then after that there is a default Constructor as well like what you can do is by default like if you just make a student class let's say St Dent student okay then what you do is you just open close it right so this will be a default Constructor and now what I will do is let's say I will declare another student object let's say student let's say st2 is equal to uh new student okay and then I'll open close it so now this student uh object has been made so st2 student object has been made here okay now let me zoom in a bit okay so this st2 student object has been made here uh and I hope that screen is clearly visible okay now if I want to update it on the go so what I can do is I can say that St do. name is equal to what let's say anit okay then after that let's say if I had to update section so st2 do uh let's say I'll update the section as what let's say something like uh B okay and then what I will do is let's say st2 do roll number I'll update as what let's say I'll update this as uh anything but 54 okay anything let's say as 54 and then when I'll print uh this thing so let's let me just copy the print state M and let me use them again suppose I'm copying this and I will now print st2 do R number st2 do name st2 do section so now this when I'm making the st2 object so default Constructor is being called uh in which I was not passing anything and here I can update the object like this uh okay so when I'll run this code so you will see that the second output will also be there okay for okay so I sorry I have given it in characters I should give 54 in integer only okay now let's try and run this code also and see how it's working okay so yeah you can uh okay now it's okay so I need to give this as 54 now let's try and run it again okay so you can clearly uh okay st2 do section okay I've used Double C here let me just remove it now I guess it would uh run properly okay let's see so yeah you can see that for the second object I had given the role number as 454 name as anit and section as B so is everyone clear so far you can write clear in the chat is everyone clear what are objects and what are uh like uh this thing uh what is object what is Constructor what is class blueprint and everything okay so this is how I like to teach and this is how I want to introduce you to objectoriented programming because see you come across like everyone would agree with me everyone will agree with me I know that that we all come across this non-primitive data type okay everyone comes across this thing that is nonprimitive data type but when do we use it for example if you have a tree also right so my question is why do we have to create a Constructor and instance why you just do the print value directly from class like example you declared RO number name but see the thing is that if I want see the thing is that I might want to store an array of student suppose for every student I want to store so I will declare what can I say that in that case I will declare an ARR of student so student let's say I will make a St object because if I need a all lot of students so I will make a uh make a array of student St is equal to new and then I then I will pass what student here right normally in AR what do you pass you pass int ARR okay uh is equal to new in um then what you do is you declare the size as n okay here suppose you have to store the data for n students okay so for the student zero you can store the name role number and section then student at index one also you'll be able to store so these things if you want to do efficiently now when the thing is you need to understand that uh in complicated systems right uh Whenever You're Building a large scale system so it like as of now you are an individual so you are only thinking that uh you will only need one or two uh one or two element so why not print them directly but later on when your uh when your application will be used on scale then you need to take care of all these things also now that is why okay so you cannot you just should not directly print because if I ask you to print for second student or third student or something so how you will do that now so those things are there and you will use the data for them also so so you can see when you will make the student object now so now there will be a lot of student objects that will be there okay and they will be storing the name role number and everything clear with this uh okay uh so everyone is clear so far you can tell me guys and then we can proceed further okay uh yeah so uh great I guess everyone is clear so far right so now coming to this uh next thing that is encapsulation right so I'll explain encapsulation what is encapsulation so what happens is if I have to check uh whether uh like if suppose that what I do is uh like if you will see so what is encapsulation basically what is encapsulation so encapsulation is nothing but it is the wrapping of data into a single unit okay so data and functions also right so if you will see here guys can I say that I have encapsulated if you will see a capsule right have you ever seen a normal capsule if you have seen a capsule guys can I say that maybe in one part something is filled and in another part some other color some other medicine is filled have you seen that in real life where yes or no I guess you must have seen it have you filled this thing in one part there's something else filled and in a capsule in another part there's something else filled right so similarly what I'm saying is uh basically objectoriented programming is also encapsulation right class making a class object is also encap encapsulated because here you have the name okay in the same entity then you have the role number also then let's say you have what you have the section as well right so you have encapsulated all the data types into a single entity so that is clear why this is called encapsulation and what is the concept of encapsulation is that clear to everyone guys yes or no please tell me okay I hope that encapsulation part is clear now basically there are two things right there is like for every object like like uh you can have functions also right suppose that if I will include for every like I will include a parameter as a let's say marks okay so I'll let's say for every student I will also score marks of a particular subject let's say that can be mathematics so for every student if I include marks as well now then then what I then what I need to do is let's say I will make a function here okay and the function will be what let's say pass or fail let's say that function will determine if a student is passing or fail okay so pass or fail is a function that I will call here suppose and here what we will do is uh let's say it will be Boolean type okay so let's type it as boan here okay so I can make a function pass or fail okay and then what I can do is if I have the mark so suppose that if the marks if the marks of the student is what guys if the uh like if I want to check pass or fail kind of thing so what I can do I can say that if the marks is what uh if the marks is greater than equal to 40 then then I might return a true from this function okay indicating that the student has passed right so TR r u e okay else what I can do is I can return false here okay that the student is not passing so suppose what I'll do is I'll create another parameter let's say uh M uh okay then I'll update the marks as M so marks is equal to M here right now this is basically functions are also like you you can make functions out of it out of it as well right so if I want to check whether the student is passing or failing here right so now what I'll do is in marks let's say for the first student I'm passing the passing the marks as how much let's say as 35 uh let's say 36 okay and for the second student let's say what I'll do is st2 do marks I'll update as what guys I'll update for the second student I'll update the marks as uh something like uh let's say 71 okay now uh if you will see here instead of printing these things now what I will do is I'll print for the first student student so let's say system do out. print Len okay and then what I'll do is st. name uh then plus okay so I'll check whether it is passing or failing so st2 like I'll call for st2 do pass or fail so I'm calling the function for this guy and it will be checked whether this guy is passing or not okay the student the first student then after that I will again do this for the second one so that you can clearly understand so okay so then I'll do st2 do name I'll check like I'll print the name of this guy and then I will also do what uh St dot st2 dot I'll call this function pass or fail for this guy as well okay so this is what I'm planning to do here now uh if I will run this code so I hope that I not made any any uh syntax mistakes if I if I haven't then it will give for First Student it will give fail and for second it will give uh okay I should have added a plus now I'll try to recompile it okay let me just do it again yeah so you can see here that for yes I'll try to compile it again for you uh you can see that again okay so you can see for yes it is returning false and for anit it is returning true because if you will see here guys what have I done like see all of you understand the pass or fail function logic okay because in this function what I've done is if the marks is greater than equal to 40 then I'm returning a true otherwise I'm returning a false right so uh like I have see encapsulation is not only encapsulation is not only that you have uh uh you have collected all the different data types that are there okay that is for a student you can have name role number marks and all those things but also you can have behaviors that you can have different functions so it is encapsulated inside the same class right that is what encapsulation is that you have the different different data members and you have different different functions also for that student let's say there might be a function for calculating average or something like that so these things can be there and you can see for First Student I had given the marks as 36 and for second student I had given the marks as how much I had given the marks as 71 so you can see that yes is going to fail so when I'll call the function it will tell me that it is failing and for the next student that is for anit that is st2 when I'm calling the pass or fail function so it is returning true that it it will pass is that clear to everyone guys please write plus one so this is also uh encapsulation and is this much part clear so far everyone you can tell me okay so just let me know if you are clear so far or not are you getting getting this point yes or no let me just check in the chat uh K says yes if you have understood this please hit the like button and give me a plus one in the chat as well guys okay you should be interactive everyone should be interactive enough inside the chat uh okay so far everyone is clear so encapsulation is not only for data members right so you might have thought that we just encapsulate the name role number and section no we encapsulated the behavior also right so basically the values the behavior behavior is what functions right so you can see pass or fail function was there now that also was there inside the class then uh like you can say name was there then role number was there right and section was there obviously so does this make sense to everyone you can tell me guys and then we will uh proceed further okay so plus one uh in the chat guys and then I'll be moving forward okay so I guess this much part is clear right so now uh moving on to data abstraction right so what is data abstraction here so if you will see data abstraction is basically see uh data abstraction is one of the most efficient and essential features in object orated programming where you provide essential information about data to the like where you are only providing the essential information to the uh to the outside world okay and hiding the background details so suppose that see suppose that what you want to do is if you if you if you go to an any ATM right if you go to any ATM right if you go to any at ATM right so let's say you have your ATM card here right now when you will when you will uh let's say when you will use your like when you will use your ATM card inside the ATM then it will help you to withdraw the money right it will help you to withdraw the money right let's say it will help you to withdraw the money uh or something or anything that you want to do but it will NE like you never see what is happening behind the scenes right agree with me how the ATM machine how the software is functioning what is the code written behind the scenes how the ATM machine whatever lowlevel design code objectoriented code or whatever logical code has been written behind the scenes you don't get to see that agree with me everyone right so that is how you do abstraction there so similarly if suppose that I just I don't want to tell whether a student is getting how many number okay I just want to uh like I I just want the user suppose that uh suppose that user didn't have any idea I'm like user is only having students okay uh and the thing is that user can only call an object that so I can use abstraction here suppose that by default I had given the values to the student and this was not shown to the like by default I had given the values for the student object okay and the user is only allowed uh to check whe whether the student is passing or not and I don't want to show him the marks then I will only allow him to use the pass or fail function okay so and I will not allow him to access the marks okay uh suppose so in that case if he will only use a pass or fail function so he'll only get to know that whether the student student is passing a feeling I will hide the uh name of that like I'll hide the uh number that marks that are code by that student okay similarly if there is AAR card information like Suppose there is information about date of birth so if I just want to tell whether that person is eligible or not okay somebody can call a function okay that like is eligible or is eligible to vote I don't want to show the age of that person okay then what I will do I will do this kind of abstraction that I'll just give a function to use it and I'll not allow him to access the database behind to access the data or the Cod code base behind the scenes is that clear what is abstraction is that clear to everyone please write yes in the chat does that make sense everyone you can tell me guys uh does that make sense to you uh okay that how abstraction will be built you can see this is one basic example suppose the data was already filled in all the students object and I only allow you to use the function that is pass or fail okay then in that case the uh in that case someone will not be able to access the marks and if I want to uh hide parameters like let's say age right uh age of a person or date of birth or AAR card information then I'll not display it I'll only allow you to use the information now makes sense shalu says yes what about others so this is basically what data abstraction is all about so you can see in objectoriented programming there were several things as I already told you right there was classes then there was object data abstraction and capsulation so so far everyone is clear right with these points everyone is clear you can let me know yes or no everyone is clear so far or not guys okay so in objectoriented programming so far we discuss class then we discuss the objects then we also discussed what we discussed what is encapsulation right and then we discussed what is uh the next thing that is abstraction okay so if you don't want the user uh to uh access something right so you can just allow him to use a function and all those things makes sense Amit badw triple mut I guess yeah so yeah it reminds me about my college I I haven't still taken the degree okay makes sense okay uh right so yeah now uh What uh actually uh these things are there right but what has happened these days apart from Thea companies are also asking you lowlevel design okay so basically after this you have the inheritance and other things but obviously as of now today I will not be teaching those things okay uh because uh because I can understand the students encapsulation abstraction yeah I hope that this part is clear right so you also have inheritance right inheritance is also there so let me explain inherit inheritance by the way okay what do you mean by inheritance okay or where can you see it so that see in every organization do you agree with me like why do we need it first of all first of all you should always be scientific in nature that why do you need a certain thing okay so why do you need inheritance in the first place okay why because see if suppose that uh there is a there's an organization like let's say there is Geeks for geeks only okay there's an organization like Geeks for geeks only now what will happen in the organization is uh let's say in this organization there will be some students also right then let me use some different and then I will explain okay property of someone yeah I'll like I'll tell you I'll tell you further just give me a second let me draw some diagrams okay let's say uh I'll draw some boxes let's say three or four boxes only I'll draw here okay now the thing is guys if you will see here right suppose that there is Geeks for Geeks so obviously there will be employee of Geeks for geeks right some people would be the employee right then you will have student also there then let's say you will have someone who is class manager suppose someone like class manager is there then some someone is a mentor also at geeko Geeks right so basically uh Mentor is someone who might be from some other company but they are mentoring here right so basically for like for every employee can I say that there will be a name then there will be an age Also let's say they will be like they will be an age also right let's say there will be a name then there will be an age then there will be address also right ad SS then for uh student also if you will see so they will be what there will be a name then they will be age then there will be address okay I'm just giving a basic example then for class manager also there will be a name let's say age also will be there then his permanent address his or her permanent address for Mentor also there will be a name there will be an age right and there will be a permanent address that will be there so do like and then there will be a lot of other things written for employee student and class manager and Mentor right but do you want uh do you want to write code again and again no in an organization you don't want to rewrite the code code again and again okay so one of the purposes of inheritance is that it helps you it allows you to use the functionality okay is that clear so will you write it or not please write yes or no in the chat would you like for every see if you're make suppose that if you're making class so for employee class also would you like to have name age and address for student also would you like to have name and and address no for class manager would you like to have name address and age no for everybody you will not like to have it agree with me in in every class will you make this thing no what you can do is you can say that on the outer surface level you can make a person class okay and in that person class you can have the name then you can have what you can have the age and let's say you can have the address and some other things that you might require okay and then uh what you will do is you'll use the concept of inheritance and basically what will happen now the employee that is there okay it will inherit okay it will extend the property it will inherit the property of person so now in employee whatever logic you want wanted to write okay so in employee what do you want let's say you want employee ID right so for every employee there will be an ID okay so uh that that you can now you don't need to write the Redundant code you only need to write whatever logic is required for employees and whatever functions are there for employees okay then for similarly for student also right so for student let's say you can store what what is the College of that student and uh what is the performance and all those things right then the because it will inherit so basically you will write what let's say you will write class student then you will write extends uh extend person so basically uh what will happen is from the person class the all these other classes can inherit okay then class manager can also inherit okay then you can say that uh other person like Mentor can also inherit okay so Mentor is from which company that that you need to know and functions of Mentor let's say he's teaching something something some Java uh something like Java or he might be teaching object oriented programming or something so that is why you don't want to write the redundant code also so these are one of the examples where inheritance is used is that clear to everyone uh okay code worse uh is that clear to you others are also clear please write plus one and please hit the like button if you clear so far guys okay I hope you have understood The Inheritance also this is something I'm talking in real terms uh okay not just theoretical in nature and this is used a lot okay clear so far everyone you can just hit the like button and let me know if you're clear or not okay so yeah I guess people are saying that they are clear very good now yeah lastly uh you can see that there's one more thing that is left that is polymorphism so I'll explain polymorphism as well okay obviously there's a very basic example that is there so basically polymorphism is what suppose that uh like polymorphism is what having the same name and using it at various places right so maybe I have a function area now suppose that if I have function area so in uh in terms of area function let's say I have int s so for square the area would be what I can simply return side into side obviously I'm giving a very basic example here okay then uh let's say I might have a area function where I might be given a rectangle so for rectangle the area would be what for that I need length and breadth okay so so same function name I can use and parameters would be different here then I can return what then I can return length into breadth okay because for area the for area uh it will be nothing but for rectangle it will be length into breadth then if I want to calculate area of a circle okay then let's say I'll be given the double uh radius okay then for uh I can use the same function name here and I can return what I can return Pi R square that is 3.14 into radius into radius correct makes sense guys okay so that is what polymorphism is about uh obviously I'm not going into much of the details there there are a lot of things that lie underneath but uh this is one basic example which I'm giving so that I can make a class and like I can make like if I have some if I have some redundant operation So based on the parameters whatever parameter I'm passing so that function will be called if if inside the if inside the area function if I'm calling 5 comma four so it will understand that you have to calculate the area of a rectangle so it will return length into bread if I'm calling inside the area function if I'm passing 10 so it will calculate area of square that is 10 into 10 would be 100 and if I'm passing inside the area function if I'm passing 5.5 so it will calculate 3.14 into 5.5 into 5.5 is that clear to everyone guys uh you can just let me know if that makes sense okay so this is uh about polymorphism polymorphism can be of two types right so they can be a Dynam like polymorphism is also of two types but uh today if I'll explain it it will take a lot of time okay polymorphism is also like you can say static polymorphism is there and then Dynamic polymorphism is also there okay so like the thing that I explained about area right that is that comes under static polymorphism Dy Dynamic polymorphism is basically uh static poly polymorphism you can say say is also know known as compile time polymorphism it comes under the category of function overloading okay and then Dynamic polymorphism is there which is basically function overriding okay overriding so if like static polymorphism is clear okay so far yes or no static polymorphism or you can say function overloading part is clear then I will just explain the dynamic polymorphism to everyone as well before wrapping up okay starting is is clear please write yes in the chat and then I'll explain one example of U dynamic polymorphism as well okay so suppose that if I am making a class of toy okay suppose that what is dynamic polymorphism so dynamic means what dynamic means when you uh like when you want things to happen whenever you call them so basically suppose that if I'm making a class of toy okay inside that what I will do is let's say let's say I will make a move uh like how that uh that how that toy is going to move let's say I'll make a function move but when I'm making a class toy now so I might not know that uh what it will do exactly so I I might declare it as as abstract or as an interface here okay and then later on let's say what I will do is uh so suppose that if I have a toy toy uh as I say okay and I don't know how it will be moving how that toy will move okay as of now I don't know because it depends on the kind of toy then after that obviously toy will have a name of it and all those things other things will be there there will be a size of toy and there will be a price of the toy now suppose that I am doing what I am having let's say later on what I will have is if I will have a robot robot toy okay then how will it like how will it move can I say that it will like it will move like this understanding it will be moving in a strict fashion let's say let's say let then inside that when I will Define the move for it so I'll say that it will move in a strict fashion and all those things right it will it will move by having its hands up and down and like that okay whereas suppose that if I have another toy let's say as teddy bear okay uh t d d y Teddy beer toy if I'll have a Teddy beer toy then in the teddy beer toy how will the teddy beer move Teddy beer will uh uh how will the teddy beer move right so Teddy me will move uh like let's say slowly and let's say how the Ted whe will move it will move very slowly and not in a strict fashion it will move like an animal are you getting my point so these things are there okay for example if you have have something like let's say a vehicle uh let's say if you have bike only okay so in bike you can say that uh like you can make a function of speed okay and you might not know what you have to Define so later on uh when you will make the function out of this bike when you will do what uh when you will inherit it as a sports bike okay sports bike or you can say normal bike okay so in in those the the speed limit would be the speed would be different the gears would be different okay or let's say I know that in bikes there would be gears but in sports bike there would be a different mechanism for gear and in normal mic there will be a different mechanism so when I just want to define the function and uh I just want to I I know that there will be a gear fun gear function that will be there but it will depend on the kind of bike that I'm building okay then I will def like I will just declare the function here gear and then I will Define the gear function inside the children classes so that is what is known as Dynamic polymorphism uh okay Dynamic inheritance are you getting my point is everyone clear with this please write clear in the chat guys code words has said clear what about others others are also clear you can hit the like button guys if you're clear with this okay this is uh this is another interesting example that I just explained so we understood all the topics throughout okay so is everyone clear with all the things that I've explained so far you can tell me guys okay uh if you will see so we have discussed about classes in object oriented programming then we also discussed about objects right in terms of code only then we also discussed about uh encapsulation right then data hiding that if you don't want to show which person is passing or fa like what is the exact Max but if you just want to check whether it is passing or not okay okay so that is abstraction basically then after that what you have uh after abstraction I explained uh to you about polymorphism right now okay polymorphism can be two types Dynamic polymorphism like when uh when I gave the example of toy and area function examples where you already know so that is compile time polymorphism or static polymorphism then I also explained about inheritance right uh where the person example I give so is that clear everyone so far like did you enjoyed this session or not you can you can give me a session a rating for the session out of five what's what do you think uh out of five or out of 10 let's give a rating out of 10 okay uh give a rating to this session out of 10 okay let's see what uh how much you rate this session out of 10 just give me a rating out of 10 on this session let's see uh how you'll rate this okay sir explain interface yeah like that will be that can be covered like as I said like you can just take suras just take this as an example that whenever I I declare an interface basically when I know that there will be suppose that there will be a in bike I know there will be gear okay so I declare an interface gear but it depends if I'm building a sports bike then there I will decide there I will write all the function of the gear okay the whole functionality of gear so that is what uh is uh interface understanding my point that when the child class will decide what you have to write there all those things so that is an example of interface I hope you have got an idea in the direction in which you should think make sense okay others can also give me a quick rating and uh please hit the like button guys if you're clear so far okay because I've put in a lot of effort to explain the basic things in the simplest way possible okay and uh so before we end the session just uh let me know how this explanation was and just uh hitting the like button uh would help a lot okay so everyone is clear so far okay so yeah this was all about the session okay and I hope that everyone who's watching it please make sure to hit the like button and uh I hope that you enjoyed this session okay make sure to check out the link that is given in the description that okay so you can do what guys you can commit with gfg you can be consistent and you can do what you can commit uh with geeko geeks and basically you can be consistent uh if you do uh if you do n uh if you do a course if you do 90% of the course within 90 days okay then you will get 90% refund on Geeks for geeks courses so just in case if you want to check them out so I guess you'll find the link for them in the description okay and if there are any questions you can tell me else we are good to go for the for today okay so I guess that uh that is it okay so yeah thanks a lot everyone for uh joining for this particular session and I'll see you all in any other session today Sadat was not there so I thought let's have a handson object oriented oop session okay thank you and let me know which topics you would like me to cover would you like me to cover some interview questions on object oriented programming and things like that okay that you can tell me and that is it for today uh thank you and bye-bye guys take care all the very best thank you