HL Mastery aspects:

ADT queue

Example Queue Applet

SingtelQueue.java
CustomerNode.java
CustomerQueue.java

QueueFullException.java
QueueEmptyException.java

Whereas the stack is a LIFO (Last In First Out) structure, the queue is FIFO - First In First Out. Using a linked list we simply add (or enqueue ) items at the back and remove ( dequeue ) items from the front :

Exercise

Create a Queue Class that implements a character queue based upon the CharacterNode Class (see stacks page). The Queue should implement the methods enqueue and dequeue and throw an exception if the queue is empty.

Construct an Applet that demonstrates that your queue ADT works correctly.

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A deque

A deque (pronounced "deck") is a double-ended queue, elements may be enqueued and dequeued at either the front or the back.  So it can also be used as a double ended stack!

The deque can be used for such exotic tasks as keeping track of lists of undo and redo items in your word processor.

Example Queue Applet

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Related: [ Java home | Previous: stacks | Next: recursion ]

You can read more about queues in theory topic 5.

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