1. Set

• Set is a collection, which avoids containing duplicate ELEMENTS.
• This interface models the mathematical set abstraction and is used to represent sets, such as the deck of cards.
• Set doesn’t maintain the order.
• HashSet, LinkedHashSet or TreeSet are the implementations of the Set interface.
• Set also adds a stronger contract on the behaviour of the equals and hashCode
• Code SNIPPET: Set set = new HashSet();

2. List

• The list follows the ordered collection and can contain duplicate elements.
• One can access any element from its index.
• The list is somewhat like array however length is changing at runtime.
• List interface doesn’t provide the thread safety.
• ArrayList, LinkedList, CopyOnWriteArray are the implementation of List interface.
• Code Snippet: List list = new ArrayList();

3. Queue

• Queue interface is a part of collection framework extend the collection interface.
• A queue is used to insert elements at the end of the queue and removes from the beginning of the queue. It BASED on the FIFO concept.
• The queue is inherited from the Collection framework, so it supports all the method like insertion and deletion.
• ArrayBlockingqueue and PriorityQueue are the most widely used implementation classes.
• public class PriorityQueue<E&GT; extends AbstractQueue<E> implements Serializable  
• Code Snippet: Queue queue = new PriorityQueue();