The Collections Framework consists of three parts : Collections Framework « Collections « Java Tutorial

1. interfaces, the abstract data types that the framework supports.
2. implementations, the concrete versions of these interfaces.
3. algorithms, the predefined actions that can be defined on either the interfaces or their implementations.

1. All implementations are unsynchronized.
2. All implementations are serializable and cloneable
3. All implementations support having null elements.

The predefined algorithms for supporting the framework are found in the Collections and Arrays classes.