9 Key Interfaces of Collection Framework

     1.Collection :-

• 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.
•  In general  collection interface is considered as root interface of Collection framework.
• Note:- there is no concrete class which implements collection interface directly.

      2. List :-

•  List is 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 preserved then we should go for List.

f             3. Set :-

• Set is 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 are not preserved then we should go for Set.

              4. SortedSet :-

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

              5. NavigableSet :-

•      It is the child interface of SortedSet.
•      It defines several methods for navigable purpose.

            

              6. Queue:-

•      It is child interface of Collection.
•     If we want to represent a group of individual objects prior to processing then we should go for Queue.
•     Ex: before sending a mail all mail id’s we have to store somewhere and in which order we saved in the same order mail’s should be delivered(First in First out) for this requirement 
•      Queue concept is the best choice.

                     Note:-

•       All the above interfaces (Collection, List, Set, SortedSet, NavigableSet and Queue) meant for representing a group of individual objects.
•       If we want to represent a group of objects as key value pairs the we should go for Map Interface.

             7. Map

•         Map is not he child interface of Collection.
•         If we want to represent a group of individual objects as key value pairs then we should    go for Map. Ex : Roll no. Name
•         102 Shivaji
•         103 Anil
•         104 Chandra
•         Both key and value are objects.
•         Duplicated keys are not allowed but values can be duplicated.

             8. SortedMap

•         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 SortedMap.

             9. NavigableMap(I)

•            It is the child interface of sorted map, it defines
•            Several utility methods for navigation purpose.
•            TreeMap is the implementation class for NavigableMap.