Key interfaces in java

What are the key interfaces in java?

There are 9 key interfaces in java:

1) Collection
2) List
3) Set
4) SortedSet
5) Navigable Set
6) Queue
7) Map
8) SortedMap
9) NavigableMap

Collection(I):

• If we want to represent a group of individual objects as a single entity then we should go for collection
• Collection interface defines the most common methods which are applicable for any collection object

      Methods:         

      boolean add(Object o)

      boolean addAll(Collection c)

      boolean remove(Object o)

      boolean removeAll(Collection c)

      boolean retainAll(Collection c) -- To remove all objects except those present in c

      void clear()

      boolean contains(Object o)

      boolean containsAll(Collection c)

      boolean  isEmpty()

      int size();

      Object[] toArray();

      Iterator iterator()

• In general collection interface is considered as Root Interface of collection framework

LIST(I):

• It is the child interface of collection
• If we want to represent a group of individual objects as a single entity where duplicates are allowed and insertion order must be preserved, then we should go for List

SET(I):

• It is the child interface of collection
• If we want to represent a group of individual objects as a single entity where duplicates are not allowed and insertion order not required, then we should go for Set

Sortes Set(I):

• It is the child interface of SET
• If we want to represent a group of individual objects as a single entity where duplicates are not allowed and all objects should be inserted according to some sorting order, then we should go for Sorted Set.

Navigable Set(I):

• It is the child interface of SortedSet.
• It contains several methods for navigation purposes
• To implement a navigable set, Tree set came 

Queue(I):

• It follows FIFO i.e., First In First Out
• Prior to processing, they should go for QUEUE

** Collection, List, sorted set, set, Navigable set, Queue ---Interfaces meant for representing a group of individual objects.

MAP(I): 

• The map is not a child interface of collection.
• If we want to represent a group of individual objects as a Key, Value pairs then we should go for MAP interface.
• Both keys and values are objects only. Duplicate keys are not allowed but values can be duplicated.

Sorted Map(I):

• It is the child interface of Map.
• If we want to represent a group of key-value pairs according to some sorting order of keys then we should go for sorted Map.

Navigable Map(I):

• It is the child interface of Sorted Map.
• It defines several methods for navigating purposes.
• TreeMap is the implementation class of the Navigable map.

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