Single Responsibility Principle (SRP)

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🧠 What is the Single Responsibility Principle (SRP)?

The Single Responsibility Principle says:
A class (or method) should have only one reason to change.

In plain English:

• A class should do only one thing

• A method should do only one action

• Keep it focused and clean

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🏡 Real-World Analogy: Building a House

🚫 Bad Example: One Person Doing It All

Imagine this:

You're building a house. One guy comes in and says:
“Don’t worry! I’ll do the plumbing, electrical, architecture, painting, and interior design!”

That’s a disaster waiting to happen.

Now apply this to code:

public class House {
    void buildFoundation() { /* ... */ }
    void paintWalls() { /* ... */ }
    void installElectricity() { /* ... */ }
    void layPipes() { /* ... */ }
    void designInterior() { /* ... */ }
}

This class has too many responsibilities. If you want to change the interior layout, you might break the plumbing. Not good.

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✅ Good Example: Each Class Has One Job

Just like a real house project has:

• A Plumber

• An Electrician

• A Painter

• An Architect

We split our Java classes too:

public class FoundationBuilder {
    void buildFoundation() { /* logic */ }
}

public class Painter {
    void paintWalls() { /* logic */ }
}

public class Electrician {
    void installElectricity() { /* logic */ }
}

Now each class has one reason to change. If someone changes how painting works, they don't mess up the wiring.

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🎯 What About Methods?

🚫 Bad Method Example (Too Many Jobs)

void buildHouse() {
    buildFoundation();
    paintWalls();
    installElectricity();
    designInterior();
}

It’s like a meeting that tries to solve every problem at once — confusing!

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✅ Good Method Example (One Action per Method)

void buildFoundation() { /* ... */ }
void paintWalls() { /* ... */ }
void installElectricity() { /* ... */ }

Now each method does one job, is easier to test, and less likely to break.

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🔁 Real-World Mapping

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✍️ Final Takeaway

Code like you're hiring workers to build your house.
Don't hire one person to do it all.

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📢 Bonus Developer Tip

✅ Smaller classes = Better code.
✅ Easier to test, reuse, debug, and maintain.

“SRP is not about splitting everything — it’s about grouping code by what changes together*.”*

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