6. Collection interfaces

• Collection Interfaces are abstract data types that represent collections.

  
  Collection // supports conversion between different collection types and arrays
  Set        // a collection that cannot contain duplicate elements
  List       // a sequence of elements
  Queue      // a collection of multiple elements held prior to processing
  Map        // a collection of mappings that map keys to values
  SortedSet  // a set that maintains its elements in ascending order
  SortedMap  // a set that maintains its mappings in ascending order
  
  

  Interfaces allow collections to be manipulated independently of the details of their representation (implementation).

• In object-oriented languages, interfaces generally form a hierarchy.