README.md

🪶 Flyweight

Category: Structural

📖 Description

The Flyweight pattern reduces memory usage by sharing as much data as possible with similar objects.

🛠️ Purpose: Optimize memory use when many objects share common data.

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🔧 Structure

classDiagram
    class Flyweight {
        +operation(String extrinsicState)
    }
    class ConcreteFlyweight
    class FlyweightFactory {
        +getFlyweight(String key): Flyweight
    }

    Flyweight <|-- ConcreteFlyweight
    FlyweightFactory --> Flyweight

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💻 Java 21 Example

Flyweight Interface

public interface Flyweight {
    void operation(String extrinsicState);
}

Concrete Flyweight

public final class ConcreteFlyweight implements Flyweight {

    private final String intrinsicState;

    public ConcreteFlyweight(final String intrinsicState) {
        this.intrinsicState = intrinsicState;
    }

    @Override
    public void operation(final String extrinsicState) {
        System.out.println("Intrinsic: " + intrinsicState + ", Extrinsic: " + extrinsicState);
    }
}

Flyweight Factory

import java.util.HashMap;
import java.util.Map;

public final class FlyweightFactory {

    private final Map<String, Flyweight> flyweights = new HashMap<>();

    public Flyweight getFlyweight(final String key) {
        return flyweights.computeIfAbsent(key, k -> new ConcreteFlyweight(k));
    }
}

Usage

public final class Demo {
    public static void main(final String[] args) {
        FlyweightFactory factory = new FlyweightFactory();
        Flyweight flyweight1 = factory.getFlyweight("A");
        Flyweight flyweight2 = factory.getFlyweight("A");
        flyweight1.operation("First call");
        flyweight2.operation("Second call");
    }
}