Flyweight pattern has has structural purpose, applies to objects and uses sharing to support large numbers of fine-grained objects efficiently. The pattern can be used to reduce memory usage when you need to create a large number of similar objects.
- when one instance of a class can be used to provide many "virtual instances"
- 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