Implementations in collections

Implementations are the actual data objects used to store collections, which implement the core collection interfaces described in the previous lesson. The sections that follow describe three kinds of implementations:

General-purpose Implementations

General-purpose implementations are the public classes that provide the primary implementations of the core collection interfaces.

Wrapper Implementations

Wrapper implementations are used in combination with other implementations (often the general-purpose implementations) to provide added functionality.

Convenience Implementations

Convenience implementations are mini-implementations, typically made available via static factory methods that provide convenient, efficient alternatives to the general-purpose implementations for special collections (like singleton sets).

Additionally, you can build your own implementations, based on the JDK's abstract implementations. This is described in a separate lesson because it's an advanced topic. It's not particularly hard, but relatively few people will need to do it.