Use sharing to support large numbers of fine-grained objects efficiently.
The Flyweight pattern's effectiveness depends heavily on how and where it's used. Apply the Flyweight pattern when all of the following are true
- an application uses a large number of objects
- storage costs are high because of the sheer quantity of objects
- most object state can be made extrinsic
- many groups of objects may be replaced by relatively few shared objects once extrinsic state is removed
- the application doesn't depend on object identity. Since flyweight objects may be shared, identity tests will return true for conceptually distinct objects.
Real world examples
- java.lang.Integer#valueOf(int) and similarly for Byte, Character and other wrapped types.