Design Patterns | Flyweight

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1. References
2. Example
   • The Flyweight
   • The Factory
   • A simple class to test the Flyweight design pattern

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1. 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.
     
2. 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)); } }