Queue example in java

Before going into the details of this program, it is advised to go through Queue Fundamentals where queue basics were discussed.
Following are some methods that do the similar operations.

• boolean offer(Object obj): Adds the element obj to the queue. If the addition is successful, the method returns true else false.
• Object poll(): Returns the head (first) element and also deletes it. That is, we cannot get it again. If no element exists (when queue is empty), the method returns null.
• Object remove(): It also returns and deletes the head element like poll(), but with a small difference. This method throws NoSuchElementException if the queue is empty.
• Object peek(): Returns the head element but it does not delete it. That is, we can get it again. Returns null when the queue is empty.
• Object element(): It works similar to peek() but with a small difference (returns but does not delete the element). It throws NoSuchElementException when the queue is empty.

offer() method is equivalent to add() method of Collection interface.
http://way2java.com/collections/queue-programming/

Queues in java

interface Queue was introduced with JDK 1.5 and is part of collections framework as Queue extends Collection interface. Queue stores elements in such way it returns the first one added. Queue follows the style of FIFO (first in, first out, remember stack follows LIFO, last in, first out). The first element in the queue is known as head and the last one is known as tail. New elements are added to the tail.
Following is the signature
public interface Queue extends Collection As queue is a subclass of Collection, it can make use of all the methods of Collection and also the extra defined in its own such as inserting, retrieving and checking the elements.
Queue vs List
The major variation is that list allows retrieving the elements from any position. But, queue follows FIFO. LinkedList implements both interfaces List and Queue.
Programming Tip: Queue allows null elements. But do not add null as the return type of poll() method is also null when the queue is empty. The return null value may confuse (or conflict) with the actual null value you have added.
Realtime examples of Queue

• Job Seekers Queue: Imagine a number of participants, aspiring job, appearing for interview. They stand in a queue. The first one stood (head) in the queue comes out first and attends the interview. The participant who comes late joins at the last of the queue (tail). While queue moves on a number check points may be there to check their bonafides and marks lists etc. Care must be taken one participant cannot be checked by many at a time or one checking person cannot check a number of participants at a time. For this a synchronized queue (java.util.concurrent.BlockingQueue) exactly suits.
• Cinema Tickets Queue: A person who stands first in the booking counter leaves first.