The collections framework in
java.util provides a number of generic classes for sets of data with functionality that can't be provided by regular arrays.
Collections framework contains interfaces for
Collection<O>, with main sub-interfaces
Set<O>, and mapping collection
Map<K,V>. Collections are the root interface and are being implemented by many other collection frameworks.
collections package provides several specialized, flexible collection types that are both high-performance and provide alternatives to the general collection types of
set. The module also defines abstract base classes describing different types of collection functionality (such as