Class MessageQueue

java.lang.Object

MessageQueue

public class MessageQueue
extends java.lang.Object

This class creates a queue (FIFO) as a linked list using MessageListNodes. The queue keeps track of its first and last node, so that the add, remove, peek, and isEmpty are all O(1). The queue just has the required queue functions: the constructor, add(), remove(), isEmpty() and peek().

Author:

AnneMarie Caballero (annemariecabs)

Field Summary

Fields

Modifier and Type	Field	Description
private MessageListNode	first	The first node in the queue, which is also where the nodes will be removed from
private MessageListNode	last	The last node in the queue, which is also where the nodes will added after

Constructor Summary

Constructors

Constructor	Description
MessageQueue()	Constructs a MessageQueue, setting both the first and last node pointers to null

Method Summary

Modifier and Type	Method	Description
void	add(Message msg)	Adds a Message to the queue
boolean	isEmpty()	Returns whether the queue is empty
Message	peek()	Returns the first Message in the queue (without removing it); which should be the first one added to the queue (FIFO)
Message	remove()	Returns and removes the first Message in the queue, which should be the first one added to the queue (FIFO)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

first

private MessageListNode first

The first node in the queue, which is also where the nodes will be removed from

last

private MessageListNode last

The last node in the queue, which is also where the nodes will added after

Constructor Detail

MessageQueue

public MessageQueue()

Constructs a MessageQueue, setting both the first and last node pointers to null

Method Detail

isEmpty

public boolean isEmpty()

Returns whether the queue is empty

Returns:

true, if there are no nodes in the queue, false otherwise

add

public void add(Message msg)

Adds a Message to the queue

Parameters:

msg - the Message to be added

peek

public Message peek()

Returns the first Message in the queue (without removing it); which should be the first one added to the queue (FIFO)

Returns:

the first Message in the queue and null if the queue was empty

remove

public Message remove()

Returns and removes the first Message in the queue, which should be the first one added to the queue (FIFO)

Returns:

the first Message in the queue, null if queue is empty