JAVA
Collections in java is a framework that provides an
architecture to store and manipulate the group of objects.
All the operations that you perform on a data such as
searching, sorting, insertion, manipulation, deletion etc. can be performed by
Java Collections.
Java Collection simply means a single unit of objects. Java
Collection framework provides many interfaces (Set, List, Queue, Deque etc.)
and classes (ArrayList, Vector, LinkedList, PriorityQueue, HashSet,
LinkedHashSet, TreeSet etc).
What is Collection framework
A collections framework is a unified architecture for
representing and manipulating collections. All collections frameworks contain
the following −
Interfaces − These are abstract data types
that represent collections. Interfaces allow collections to be manipulated
independently of the details of their representation. In object-oriented
languages, interfaces generally form a hierarchy.
Implementations, i.e., Classes − These are the concrete
implementations of the collection interfaces. In essence, they are reusable
data structures.
Algorithms − These are the methods that
perform useful computations, such as searching and sorting, on objects that
implement collection interfaces. The algorithms are said to be polymorphic:
that is, the same method can be used on many different implementations of the
appropriate collection interface.
Hierarchy of Collection Framework
Let us see the hierarchy of collection framework.The java.util package contains all
the classes and interfaces for Collection framework.
Two ways to iterate the elements of collection in
java
By Iterator interface.
By for-each loop