📅Week-4 (Day-2) - Simplifying Design: Facade Pattern with Real-World Code and Use Case

NOTE: - I started my 8-week system design journey with Coder Army. I will be journaling every day, recording what I learn, reflecting on it, and sharing it with my network to help newcomers to system design.

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💠 What is the Facade Design Pattern?

The Facade Pattern provides a simplified, unified interface to a set of complex subsystems. It hides system complexity and only exposes what's necessary.

(Hindi: Facade Pattern ek simplified aur unified interface provide karta hai jo kai complex subsystems ke upar kaam karta hai. Ye system ki complexity ko chhupa deta hai aur sirf wahi cheezein dikhata hai jo zaroori hoti hain.)

💠Facade vs Adapter

• Facade: Hides complexity

• Adapter: Bridges two incompatible interfaces

💠Real-Life Analogy

💻 Booting up a computer When you press the power button on your laptop, you don’t manually:

• Start the power supply 🔋

• Cool the system ❄️

• Load the BIOS ⚙️

• Spin up the hard disk 💽

• Boot the OS 💻

➡️ Instead, the power button does all that for you. That's Facade Pattern in real life — it hides complexity behind a simple interface!

💠 Principle of Least Knowledge (Law of Demeter)

"Talk only to your immediate friends." A class should only call methods of:

• Itself (this object)

• Objects passed in as parameters

• Objects it creates inside

• Its direct components (HAS-A relationship)

💡 This reduces dependency and keeps the system loosely coupled.

💠Subsystems in Our Example:

1. PowerSupply 🔋

2. CoolingSystem ❄️

3. BIOS ⚙️

4. HardDrive 💽

5. OperatingSystem 🖥️

These components work together to boot up a computer.

// Subsystems
class PowerSupply {
    public void providePower() {
        System.out.println("Power Supply: Providing power...");
    }
}

class CoolingSystem {
    public void startFans() {
        System.out.println("Cooling System: Fans started...");
    }
}

class CPU {
    public void initialize() {
        System.out.println("CPU: Initialization started...");
    }
}

class Memory {
    public void selfTest() {
        System.out.println("Memory: Self-test passed...");
    }
}

class HardDrive {
    public void spinUp() {
        System.out.println("Hard Drive: Spinning up...");
    }
}

class BIOS {
    public void boot(CPU cpu, Memory memory) {
        System.out.println("BIOS: Booting CPU and Memory checks...");
        cpu.initialize();
        memory.selfTest();
    }
}

class OperatingSystem {
    public void load() {
        System.out.println("Operating System: Loading into memory...");
    }
}

// Facade
class ComputerFacade {
    private PowerSupply powerSupply = new PowerSupply();
    private CoolingSystem coolingSystem = new CoolingSystem();
    private CPU cpu = new CPU();
    private Memory memory = new Memory();
    private HardDrive hardDrive = new HardDrive();
    private BIOS bios = new BIOS();
    private OperatingSystem os = new OperatingSystem();

    public void startComputer() {
        System.out.println("----- Starting Computer -----");
        powerSupply.providePower();
        coolingSystem.startFans();
        bios.boot(cpu, memory);
        hardDrive.spinUp();
        os.load();
        System.out.println("Computer Booted Successfully!");
    }
}

// Client
public class FacadePattern {
    public static void main(String[] args) {
        ComputerFacade computer = new ComputerFacade();
        computer.startComputer();
    }
}

💠Real-Life Facade Examples:

• 🏠 Home Automation: One button to turn off lights, lock doors, and activate security.

• 🎮 Game Console: One button powers on the screen, audio, and console.

• 🎬 Media Player: One button to load movie, subtitles, and audio settings.

📚 Summary

Facade Pattern kya karta hai?

Complex system ke upar ek simple interface deta hai jisse use karna easy ho jata hai.

Kab use karein?

Jab system ke multiple components ho, aur aap client ko sirf ek simple method dena chahte ho.

Kaise kaam karta hai?

Ek Facade class banao jo sare subsystems ko internally control kare. Client sirf usse interact kare.

Example: Computer ko ON karne ke liye sirf power button dabana — that’s Facade Pattern!

Week - 4 ( Day-2) Completed ✅ System Design

NOTE : - A big thanks to my mentors Rohit Negi Sir and Aditya Sir for launching this amazing 8-week course absolutely free on YouTube via CoderArmy9 :- youtube.com/@CoderArmy9 . 🙌

👉 Share this blog with your connections! Let’s keep learning, growing, and supporting one another on this journey. 🚀

✍️ Payal Kumari 👩‍💻

Jai Hind 🇮🇳 | #CoderArmy #LearningInPublic #SystemDesign #TechForAll #MentorshipMatters #8weeksLLdChallenge #LowLevelDesign #Code #LLD #OOP 👩‍💻