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Flyweight

Difficulty-Intermediate Gang Of Four Java Performance Structural

Intent

Use sharing to support large numbers of fine-grained objects efficiently.

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Applicability

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

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