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.

• List
• Sets
• Queue

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:

• ArrayList
• Linked List
• Vector

ArrayList

• It provides us dynamic arrays.
• It implements the List interface.
• The Arraylist class will allow duplicate elements.
• The Arraylist class maintains insertion order.

Linked List

• It is a linear data structure.
• Linkedlist class will allow duplicate elements.
• Linkedlist class maintains insertion order

Vector

• It is a synchronized class.
• It is a legacy class.
• It contains many legacy methods.

The implementation Class of sets is HashSet

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

• 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.

• Comparator()
• Headset()
• Tailset()
• subset()

Sortedset is implemented a class called TreeSet.

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.

PriorityQueue

• It objects are processed based on their priority.
• It does not allow null.
• Objects added to PriorityQueue must be comparable.

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