Java Collections Framework

The Java Collections Framework is a set of classes and interfaces for storing and manipulating the groups of data into a single unit. The Collection Framework reduces the programming efforts and increases the performance.

The hierarchy diagram above outlines the primary list of interfaces and classes available in java.util package.


The Collection interface is one of the root interfaces in the Java collection framework.


java.util.Set is subtype of the java.util.Collection interface. Set does not allow duplicate elements.

The list below are the Important classes of Set Implementations

  • HashSet
  • TreeSet
  • LinkedHashSet


List allows duplicate elements and the examples below are the important classes of List implementations.

  • ArrayList
  • LinkedList
  • Vector
  • Stack


The map does not extend the Collection Interface. Map allows to add the elements as a key and values pair.

The classes that implement map are as follows:

  • HashMap
  • HashTable
  • LinkedHashMap
  • TreeMap