🧬Prototype Pattern – Overview

🧠 Concept

The Prototype Pattern creates new objects by cloning existing ones (prototypes), instead of creating them from scratch.

💡 Think of it as “copy–paste” object creation — efficient when initialization is expensive or complex.

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🧱 Key Roles

Role	Description
Prototype	Declares a cloning interface (e.g., clone() method).
ConcretePrototype	Implements the cloning method.
Client	Uses the prototype to create new objects by copying existing ones.

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💻 Java Example – UI Button Prototype

// ----- Prototype Interface -----
interface UIComponent extends Cloneable {
    UIComponent clone();
    void render();
}

// ----- Concrete Prototype -----
class Button implements UIComponent {
    private String color;
    private String label;

    public Button(String color, String label) {
        this.color = color;
        this.label = label;
    }

    // Clone method
    public UIComponent clone() {
        return new Button(this.color, this.label);
    }

    public void render() {
        System.out.println("Button: " + label + " [" + color + "]");
    }
}

// ----- Another Concrete Prototype -----
class Checkbox implements UIComponent {
    private boolean checked;

    public Checkbox(boolean checked) {
        this.checked = checked;
    }

    public UIComponent clone() {
        return new Checkbox(this.checked);
    }

    public void render() {
        System.out.println("Checkbox: " + (checked ? "Checked" : "Unchecked"));
    }
}

// ----- Client -----
class PrototypeRegistry {
    private Map<String, UIComponent> prototypes = new HashMap<>();

    public void register(String key, UIComponent prototype) {
        prototypes.put(key, prototype);
    }

    public UIComponent create(String key) {
        UIComponent prototype = prototypes.get(key);
        return prototype != null ? prototype.clone() : null;
    }
}

✅ Usage Example:

public class Main {
    public static void main(String[] args) {
        PrototypeRegistry registry = new PrototypeRegistry();

        // Register prototypes
        registry.register("blueButton", new Button("blue", "Submit"));
        registry.register("checkedBox", new Checkbox(true));

        // Clone new components
        UIComponent btn1 = registry.create("blueButton");
        UIComponent box1 = registry.create("checkedBox");

        btn1.render();
        box1.render();
    }
}

Output:

Button: Submit [blue]
Checkbox: Checked

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🧠 Flow Summary

Step	Action	Result
1️⃣	Register prototype objects in registry	“Blueprints” stored
2️⃣	Client requests a new component	Registry clones the prototype
3️⃣	Client gets a fresh copy	Fast creation, same structure as prototype

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🪜 Summary

• Used when creating objects is expensive or repetitive.

• Allows cloning existing instances instead of building new ones.

• Makes adding new types easier — just register new prototypes.

• Avoids subclass explosion (no need for many factory subclasses).

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🧾 Real-world Analogy

🖨️ Document Template System

• You duplicate a “Letter Template” or “Invoice Template” instead of writing from scratch.

• The new copy (clone) can then be modified independently.

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🧭 TL;DR

Prototype Pattern = Clone existing objects to create new ones. Efficient, flexible, and reduces dependency on constructors.