The java Collection is a framework that helps in storing and manipulating a group of objects,Collections are dynamic and they can grow their size dynamically at run time as the elements are added to it.
The Collection is a root interface available in java.util.package.This is Implemented by three interfaces in Java Program.
All the above three are data structures that allow to store and manipulate objects. And each one of them has slight differences.
List –List allows duplicate objects.
Sets – Does not allow duplicate objects.
Queue–It is a First in First out Data structure.
Implementation classes of Lists:
- Linked List
- It provides us dynamic arrays.
- It implements the List interface.
- The Arraylist class will allow duplicate elements.
- The Arraylist class maintains insertion order.
- It is a linear data structure.
- Linkedlist class will allow duplicate elements.
- Linkedlist class maintains insertion order
- It is a synchronized class.
- It is a legacy class.
- It contains many legacy methods.
The implementation class of sets is HashSet
- Hashset stores the elements by using a mechanism called hashing.
- Hashset does not allow duplicate elements.
- Hashset class is non synchronized.
Hashset is implemented by another class called LinkedHashset.
- LinkedHashSet maintains the order of element (*Note wherever you found a linked keyword, It will maintain insertion order of element)
- LinkedHashSet class is non synchronized.
SortedSet is a child interface of sets.
- Sortedset is an interface in collection.
- All elements inserted into a sorted set must implement the Comparable interface.
- Sortedset has some useful methods a few mentioned below.
Sortedset is implemented a class called TreeSet.
- Treeset It will sort in ascending order.
- TreeSet class does not allow duplicate elements.
- TreeSet class is non synchronized.
Priority queue is the class that implements the queue interface.
- It objects are processed based on their priority.
- It does not allow null.
- Objects added to PriorityQueue must be comparable.