Design Patterns - Flyweight

Design Patterns | Flyweight

References
Example

References
- Definition: (source: http://en.wikipedia.org/wiki/Flyweight_pattern)
  
  A flyweight is an object that minimizes memory use by sharing as much data as possible with other similar objects; it is a way to use objects in large numbers when a simple repeated representation would use an unacceptable amount of memory.

Example

The Flyweight:

public class Entity {
    private final String id;

    public Entity(final String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }
}

The Factory:

public class EntityFactory {
    private static final Map<String, Entity> entities = new HashMap<String, Entity>();

    public static Entity getEntity(final String id) {
        final Entity entity;

        if (entities.containsKey(id)) {
            entity = entities.get(id);
        } else {
            entity = new Entity(id);
            entities.put(id, entity);
        }

        return entity;
    }
}

A simple class to test the Flyweight design pattern:

public class FlyweightPatternTest {
    public static void main(String[] args) {
        Entity entity11 = EntityFactory.getEntity("1");
        Entity entity12 = EntityFactory.getEntity("1");

        System.out.println(entity11.equals(entity12));
    }
}