12.2. Implementing CollectionThere are no concrete implementations of Collection. The class AbstractCollection, which partially implements it, is one of a series of skeletal implementationsincluding AbstractSet, AbstractList, and so onwhich provide functionality common to the different concrete implementations of each interface. These skeletal implementations are available to help the designer of new implementations of the Framework interfaces. For example, Collection could serve as the interface for bags (unordered lists), and a programmer implementing bags could extend AbstractCollection and find most of the implementation work already done. |