2. Strategy Design Pattern explanation | LLD System Design #1 | Design pattern explanation in Java

Hi, in this video we have covered #strategy #designPattern out of many design pattern which is asked in Low level system design interview.
➡️ Become a Member: / @conceptandcoding

[@swarajshelavale4830]

Best Explanation ever... You simplified 1 design pattern in just 15mins..Worth it Content!!

[@tastaslim]

Thank you for this tutorial. Just to add, The fundamental of every design pattern is to separate out what changes over period of time from what remains constant. As you see in Strategy pattern, we are trying to separate out dependency of drive from the main class as much as possible by making various strategies to inject it dynamically based on client requirement so that in future if new requirement for drive comes, there will be minimal/no changes in existing code(Open closed Principle).

[@niwanshumaheshwari4534]

Favour composition over inheritance. Separate what stays the same from what changes. As we are using a new operator, it's a program to an implementation not to an interface. We can use the factory pattern here. Right?

[@farukhmahammad9374]

@@niwanshumaheshwari4534 using new operator doesn't mean we are programming to an implementation ; it's about how you're using it in relation to abstraction and interfaces. correct me if I'm wrong.

[@tastaslim]

@@niwanshumaheshwari4534 Also you client should be the one who should initialize the class. You can inject your classes using types in static type languages and using type hints in python

[@kalpeshsaubhri]

Bhai the best thing I like about your video is breadth you cover and the language hindi. Please keep these 2 things intact

[@abhishekpattnaik8531]

Great explanation with simple example. Thanks Shrayansh.

[@noobCoder26]

I got rejected in an interview because of the lack of knowledge of design pattern. Going to learn from you next time will make a stronger comeback . 💥💥

[@ConceptandCoding]

thank you, yes let's keep practising.

[@nigyban-theallrounder9016]

Did you make a comeback

[@anuragshukla4260]

😂😂​@@nigyban-theallrounder9016

[@Rahulverma-zt3sx]

bhai comeback hua?

[@Sachin-je7ue]

bhai comeback hua ya nhi ?

[@AKASHSONI21]

Thanks for this. Your way of explaining the concepts is very explanatory

[@siddharthtripathy3964]

Kya gazab channel hai ye. love his explanation.

[@ugempireninjaaaaaahatori6755]

litreally , amazing content , from monday there will be my interviews , if i will get selected than i will defenatly return to this video and comment over this .......amazing one

[@deepanshukumar3943]

That's what we call the way to teach the Patterns. Awesome way to teach with Amazing content. Hats off..

[@ConceptandCoding]

Thanks 👍

[@garvitsingh2593]

this guy deserves a lot of respect please continue it ...a legend

[@ConceptandCoding]

thanks

[@anuragparla4201]

I wish I had this available during my last semester. Design patterns would have been a breeze. Looking forward for more content :)

[@ConceptandCoding]

Thank you. Pls also share it with your connections :)

[@adityarout1276]

If you are looking for C++ code : using namespace std; #include #include using namespace std; class drivestratergy{ public: virtual void drive()=0; }; class normalDrive : public drivestratergy{ public: void drive(){ cout

[@nikhilmeena7258]

nice

[@danishsinghjamwal627]

Thanks

[@RP-qv9sc]

thank you so much bro

[@nishaaa_maurya]

Thanks Bhai ❤

[@nishaaa_maurya]

Bro, do you have code of Observer Design Pattern of this lecture.

[@mannusharma4620]

Just day 2 in your playlist and seriously brother hats off!!! Great work....

[@connectarunkumar]

You are correct. My interview got scheduled for 3 hrs(F2F) but got finished in 15mins. I felt very bad at that moment. Many times I tried but was not able to catch concepts of design patterns. I always use to think in C with classes. Your Design pattern tutorial is helping me a lot to understand. Converting your code from java to C++ to and understanding the concepts of design patterns. Started learning now. Thanks for explanations.

[@neha6000]

Very nice explanation thanks

[@user-og7de8ih4f]

In laymen terms, In Startegy Design pattern we create an interface and it's different implementation based on strategy !! And inject appropriate startegy in client class by creating constructor or any injection of your choice

[@yyajupatel]

Exactly

[@nabajyotimajumdar4511]

Splendid video!

[@mukulkopulwar]

Great Explanation... Thanks for Sharing 🙂

[@ConceptandCoding]

thank you

[@shubhamagarwal1434]

Very well explained...awsome!!!

[@jinendrajain7672]

Awesome Content, I am sure it gonna teach Young Devs alot.

[@ConceptandCoding]

Thanks

[@Sandywf]

nice explanation ... please make a video on UML ,class and sequence diagram

[@abhaytiwari1615]

Awesome video. Thanks for uploading.

[@ConceptandCoding]

thank Abhay

[@umangmalhotra1222]

I have finally started going through your , LLD Playlist, and I will comment something on every video after watching. Not always need to be Praise or Learnings from the video.

[@ConceptandCoding]

Thanks Umang, really appreciate it.

[@AKASHSONI21]

Thanks for this. Your way of explaining the concepts is very well and helpful.

[@ConceptandCoding]

Glad it was helpful!

[@harshinredzone]

Thanks for sharing knowledge, Shrayansh.

[@ConceptandCoding]

Thanks 🙏

[@X_y_zaid]

Such good explanation bro 🙌🏻

[@MrBaaz-do9ny]

aap bhagwan ho... I have seen almost 5 videos on strategy pattern but this is best till now..

[@MrBaaz-do9ny]

Also continue in hindi always... its your USP... loved it

[@ConceptandCoding]

thank you

[@mayursoni346]

Good content - really appreciate your efforts in explaining the concepts. Best wishes,.

[@ConceptandCoding]

Thanks 🙏

[@shubhamrajput37]

It took me more than an hour to understand this while going through the Head First Book for the same design principle. Should have gone through the video first. Now I am going to use this "strategy", in which I will refer to your video first and then will go through the book

[@ConceptandCoding]

:)

[@sameerchoudhary8590]

What a splendid explanation. Thank you

[@ConceptandCoding]

tha

[@RaviBiradar080]

Very well explained with understandable examples👍

[@ConceptandCoding]

thanks Ravi

[@nikkm2000]

wonderful explanation dear. Just one suggestion(pls correct me if I am wrong), I think we have to give different name like myDrive() instead of drive() in Vehicle class. It will implicitly differentiate method used inside DriverStartegy.

[@ShivamSingh-mt4nr]

Thnanks bhaiya

[@neelanshgulati2643]

Great content... Keep making more videos.

[@ConceptandCoding]

thank you

[@arungoyal3795]

This is my first comment on youtube , the way explain is amazing....

[@ConceptandCoding]

thanks a lot

[@arifurlimon4060]

Very clear and detailed explanation. Please make more videos in LLD

[@ConceptandCoding]

Thank you, pls check my LLD playlist Arifur.

[@hariedits1674]

Loved the way explained. Immediately subscribed your channel

[@ConceptandCoding]

thank you

[@iamkdblue]

Jabr jst explanation bro 🎉 - aag laga diya

[@ConceptandCoding]

Thank you

[@AshishGusain17]

Thanks for the video..nice explaination

[@ConceptandCoding]

thanks

[@prajwalmahaveera9346]

This explanation was clear and damn helpful. Thanks!

[@ConceptandCoding]

thank you

[@kartikeyrana3736]

Gold mine! Gold mine! Gold Mine! this playlist is a GOLD MINE !!!

[@ConceptandCoding]

Thank you

[@naveentmyug]

very thanks sir

[@royalfitness6860]

Great explanation but I would suggest to keep interface name start with I so it will be clear to understand more 😊

[@ConceptandCoding]

noted

[@ankushladani496]

Thank you Bhaiya for this awesome explaination....

[@ConceptandCoding]

Thank you

[@rahulgunkar6308]

How come this channel has less subscriber?... You deserve more subs bro.. Nicely explained.

[@ConceptandCoding]

Totally relying on you guys:)

[@ambersinghrok]

bhai bs continue rakhna har cheez...bhut bhu help hojaegi

[@ConceptandCoding]

sure Amber

[@AmanSharma-ht5zq]

Thanks

[@nitishprasadkushwaha]

useful

[@kochu7484]

Hi, @conceptandcoding where is the git repo link for the same?

[@paritoshdadhich2954]

Thank you for the view. Got to know about the when to use and how to use

[@ConceptandCoding]

Thanks

[@sanketneema286]

Thank you so much shrayansh.

[@ConceptandCoding]

Welcome

[@babhijit]

If my application has different payment gateway options, can I use this pattern to implement the working of each payment type or simple factory pattern will suffice ?

[@kashiffiroze5066]

Same can be achieved using @Qualifier annotation of springboot?

[@theritesh973]

Awesome explanation😍

[@ConceptandCoding]

thank you

[@ashishmiglani02]

Why can we not assign NormalDriveStrategy in the Vehicle class, any how if super constructor is called from child class it will be over writing with the drive strategy provided by the child class. This will be useful to have default drive strategy defined. Suggest issue with this approach ?

[@rajdave7357]

❤❤❤❤❤ maza aagaya guru ji

[@ConceptandCoding]

Thank you

[@shreyashachoudhary480]

Super Clear!

[@ConceptandCoding]

Glad it helped!

[@namanjain2488]

Note for my future reference 5:51 -> at the same level children are using same code , code is not reusable solution -> make the common part as interface type

[@DemystifyFrontend]

Great explanation

[@ConceptandCoding]

Thanks

[@sarthakbhatia7639]

We are using strategic design pattern to share common logic in subclass. Why can't we create a util function instead of following strategic design pattern?

[@auroshisray9140]

Thank you for this tutorial.

[@ConceptandCoding]

Thanks

[@paragroy5359]

Great video

[@ConceptandCoding]

Thank you

[@chandankumar-su7ng]

thanks

[@Suraj-tz3oq]

But what if I have a Vehicle class which is interface like or a class which shouldn't be instantiated

[@padmajamahapatra5546]

Very well explained . Also can you please add other design patterns to this list ..

[@ConceptandCoding]

Hi, pld do check my LLD playlist, i have added many patterns and will add more soon

[@Mohd_Rashid_Siddiqui]

well explained.

[@ConceptandCoding]

Thanks

[@elaserph]

Cool!!!!

[@ConceptandCoding]

Thanks

[@anketpatel2312]

Easily understandable.

[@ConceptandCoding]

Thanks

[@shubhamnigam14]

very good explanation ❤

[@ConceptandCoding]

Glad you liked it

[@user-mg9vx5fo4g]

Nice explanation

[@ConceptandCoding]

Thank you

[@bhanusharma7066]

maza aagya

[@vineet4991]

This is basically Dependency Inversion Principle of SOLID?

[@ajaypolicepatil]

Hi Shreyansh, According to Liskov Substitution Principle, Don't we need to implement drive method in Passenger vehicle class as well ?

[@ConceptandCoding]

If passenger Child Class has the same behaviour as Parent class, then it can use Parent class method. If it has to add some additional benefits, then it can override the method

[@ankitkumar-qn3zy]

Is it not similar to dependency injection? Here we are replacing a method with the interface.

[@homestaysandcafes]

Sir From my knowledge we cant create objects of interface. But what I am able to analyse from above example is that we can create a has-a relationship using object of interface but we have to define the functions of interface in the class where object is declare?......Do let me know whether I am correct or not? BTW you are creating some GOD level content❤ Please don't stop, I am ready to help you in every possible way.

[@ConceptandCoding]

let me check the video Hardik and then i will be able to clarify your doubts. But one thing i can tell is this is design pattern video, so pattern defined in this, and class and their relationship will be correct as its well documented.

[@SageXperts]

We are not instantiating the object , but just declaring a variable of that type. And then assigning the value.

[@ShivamVerma02]

Hey, how does construction injection different from dependency inversion (part of SOLID ), that you explained erailer using Macbook example ?

[@ConceptandCoding]

Hi Shivam, Construction injection is the the way of setting the member variable. Dependency Inversion is the design Principle which say class should only depends on high level abstraction class

[@snehilsinha4689]

There are two basic ways of injecting dependencies (we should do this to follow the D - Dependency Inversion principal): 1. Constructor Injection (simplest one) - Where we initialise the member variable through the constructor itself. 2. Field Injection - We Inject directly into the field variables (done using Dagger/Hilt Library in Android Dev). So constructor injection is just a way to implement the Dependency Inversion Principle.

[@nishanthmekala1409]

Hi Shreyansh, Your videos are awesome. But I would like to know the below things 1. which one we should start first hld or lld? 2. In what way we should learn hld and lld? 3. How to practice these and gain hands on experiene? 4. Is it necessary to take a course after watching your videos? 5. Any order, you would reccomment to follow? Please clear my doubts Shreyansh.

[@chiragrajani1606]

Do let me know as well, I have the same doubt :/

[@FusionArcs]

You should always go ahead with the LLD first, even some companies don't have this round explicitly but then it assumed you should know these principles already. Then you go HLD. For both of them see videos on a lot of problem use cases. You will be able to grasp these concepts well

[@AmarjeetKumar-to9ub]

clear :)

[@ConceptandCoding]

Thanks

[@PRANAVMAPPOLI]

Anyone implemented this in javscript? how we can do the interface thing in js since it doesnt have one.

[@aksharbrahm4618]

One concern, Please take a look the arrows in UML diagram while showing parent child relationship arrows are pointing to parent instead of child. I have verified that those should point to child could you please comment on that. Because earlier it was confusing for me..

[@JavaLeetcodeDSA]

i have joined as a member but is not able to get github link for lld videos, how can I access it

[@geekydanish5990]

I am aware of the basics of design pattern and some common principle such (as SOLID, KISS, DRY, etc) as they come into use in writing better code in general but I want to know from an interview perspective how deep one need to go say in my case I have an experience of 1.2 years and going for an interview how low do I need to go and design when it comes to LLD, I was always skeptical about LLD to what extend can we go low, in short, does experience affects the quality of solution or is it just like DSA questions same for everyone. P.S I haven't experienced any such LLD questions so far so if you can clear things here would be really helpful And sorry long explanation 😅

[@ConceptandCoding]

Hi Danish, i can definitely tell you are good in coding and DSA. And regarding LLD, there is no Level (which you can go deep). Level might be there in HLD where you can go deeper n deeper on one part of the design, like DB design, next level is RDBMS or No SQL then next level is Master slave then next level is Partitioning then sharding etc. But for LLD, its all about how good is your understanding with Objects, from the given problem are you able to identify Actors (objects), then what all features(member variables) it should have and then function. And how these different object interact with each others / what would be their relationship. Thats what Design pattern will help and to identify when and where which design pattern need to apply, that comes with experience or practice. Sorry for the long answer 🙂

[@geekydanish5990]

​@@ConceptandCoding Hey Thanks for those kind words, I hear you and it totally make sense specially "identify Actors" and finally relationship , will take those input and start learning/practicing accordingly 🙏

[@chethan4519]

How is drive strategy different from bridge design pattern? We are basically breaking the hierarchy such that we do not have to reuse the code for each possibility rather have it as two different hierarchies, such that they scale better. Is there anything significant which I'm missing?

[@ConceptandCoding]

while both the Bridge and Strategy patterns involve breaking down hierarchies, the Bridge pattern separates abstraction from implementation, allowing them to vary independently, while the Strategy pattern encapsulates a family of algorithms, making them interchangeable. The key difference lies in their intent: Bridge focuses on separating abstraction and implementation, whereas Strategy focuses on encapsulating algorithms.

[@patel5532]

Do we need to have children at the same lever or can we use Strategy pattern between children of different level?

[@anshulgoel1940]

When the child classes directly create the specific instances of Drive Strategy, aren't they violating the Dependency principle. ?

[@vamsi4998]

Great explanation. Can you provide the git hub repo link for our reference

[@ConceptandCoding]

I have shared the gitlab link in my Channel home page only Vamsi.

[@hossainurrahaman]

I have a few queries, maybe it will sound childish but I will ask anyway. We know there are 3 types of design patterns. Creational, structural and behavioral. i) Do we need to use all of these three patterns to make a full end to end application? i) If not then Can a single type of pattern handle all of the basic scenarios (creation, responsibility assignment to object etc. iii) is there any pattern which helps more during the interview.

[@ConceptandCoding]

Hi Rahman, very good question. Let me try to elaborate: - Do we need to use all 3 types of patterns to make an end to end application. Answer is NO. Using Design pattern is not mandatory. You can build system without using any pattern and live with it if system is Readable, Scalable, Manageable etc. You dont need design pattern. Let say for solving one part of the system you need to use some pattern, you can use a pattern from any type not necessary to use pattern from all 3 types. - Single pattern for helping in Interview, thats a tough question, i would say that depend on what question you get in the interview, basics questions can be created through common design patterns like Factory,Structural. But for some specific questions like design logging system, design Notify system we need to know those patterns in advance or come up some clean design during interview itself.

[@hossainurrahaman]

@@ConceptandCoding thank you for clearing the doubts. So basically during the interview for any particular scenario, I need to start with a design pattern which will suit most with the basic requirements. And need to add any additional design pattern for any new type of requirements. Eg: If asked to create a parking lot system, and if the basic requirements are can have multiple types of cars Can have multiple floor Can have multiple entry exit I can start with something like an abstract factory or factory pattern. If by any chance we need to log these events, we can use singleton pattern. Correct me if I am wrong. Thank you once again for prompt reply.

[@namansaraswat9691]

Good video for strategy design pattern, can you please make a video where you solve a complete lld problem and show usage of strategy design pattern in the solution. If there is any solution you created in lld design that has usage of strategy design please let me know.

[@ConceptandCoding]

Hi Naman, check Design Parking Lot LLD video, i have used strategy pattern there

[@namansaraswat9691]

@@ConceptandCoding thanks for reply I am just going through that video only😄😀

[@runtime379]

OP content

[@ConceptandCoding]

Thank you

[@ijazhaider6072]

Brother, Normal Drive Strategy class would implement Drive Strategy that means it has-a relationship but in diagram it is-a relationship. Implements are always has-a and extends are is-a. Am i right or missing something?

[@preetiirrothi744]

Thanks!

[@ConceptandCoding]

Welcome!

[@ConceptandCoding]

And thank you for super thanks

[@shrutiiyyer2783]

any questions available on this strategy to practice?

[@your_name96]

Sir can you tell the topics in core java I need to cover before starting this playlist since I am coming from C++ background and want to learn real life advanced oops in java

[@ConceptandCoding]

C++ is good for learning LLD as its Object oriented language only.

[@ConceptandCoding]

but if you want to learn java, then till thread topic comes in Core java

[@your_name96]

Okay thank you sir,I asked for java as majority companies prefer having java experience

[@Mmmmmkoogfssdvbhvggg]

Why are we not creating an interface for Vehicle?

[@kashishkukreja7582]

Why don't we create Vehicle as an interface and then create 2 more interfaces SprecialCapabilitiesVehicle and NormalCapabilitiesVehicle which extends Vehicle and has default implementation for drive respectively? Now the PassengerCar implements NormalCapabilitiesVehicle and SportsCar and PassengerCar implements SpecialCapabilitiesVehicle.

[@amlanroutray288]

this is because, lets assume, later on another functionality like display() will be added and it would be same for sport cars and passenger car and not in off road car, then we can create similar strategy for display and inject them in vehicle constructor. Adding more interfaces will not be a good scalable option with increase in features.

[@tanujarora4906]

As you update and add new features, how many interfaces you will add and how many interfaces you will refactor? That is the reason we should not opt for this.

[@anookimmidisetty2939]

@Concept can you share the source code as well ? seems like in your gitlab, there is no code for Strategy design pattern one..

[@ConceptandCoding]

I haven't added that, will add it soon

[@AmanSharma-vb5jl]

Love u 3000 bro

[@ConceptandCoding]

thank you

[@karankaira]

if base class has many functions then it is violatiing S of SOLID principles ? am i correct

[@ConceptandCoding]

No, for everyone function we can not create a new class. Else we will create another problem called class explosion. We can keep related functions in one class.

[@rajaryan7566]

Hello bhaiya 🙏, I need one advice, is it okay to use Python for LLD in an interview? do you think it gives us a setback if we use python?

[@ConceptandCoding]

No impact buddy, it's an OOPs language, it can be used.

[@abhinavkumar7730]

Where can i find the github repo for reference?