edu.colorado.collections
Class ArrayQueue<E>

java.lang.Object
  edu.colorado.collections.ArrayQueue<E>

All Implemented Interfaces:

java.lang.Cloneable

public class ArrayQueue<E>
extends java.lang.Object
implements java.lang.Cloneable

An ArrayQueue<E> is a queue of references to E objects.

Limitations:

(1) The capacity of one of these queues can change after it's created, but the maximum capacity is limited by the amount of free memory on the machine. The constructor, add, clone, and union will result in an OutOfMemoryError when free memory is exhausted.

(2) A queue's capacity cannot exceed the maximum integer 2,147,483,647 (Integer.MAX_VALUE). Any attempt to create a larger capacity results in a failure due to an arithmetic overflow.

Java Source Code for this class:

http://www.cs.colorado.edu/~main/edu/colorado/collections/ArrayQueue.java

See Also:

LinkedQueue

Constructor Summary

ArrayQueue()
Initialize an empty queue with an initial capacity of 10.

ArrayQueue(int initialCapacity)
Initialize an empty queue with a specified initial capacity.

Method Summary

void	add(E item) Insert a new item in this queue.
ArrayQueue<E>	clone() Generate a copy of this queue.
void	ensureCapacity(int minimumCapacity) Change the current capacity of this queue.
int	getCapacity() Accessor method to get the current capacity of this queue.
boolean	isEmpty() Determine whether this queue is empty.
E	remove() Get the front item, removing it from this queue.
int	size() Accessor method to determine the number of items in this queue.
void	trimToSize() Reduce the current capacity of this queue to its actual size (i.e., the number of items it contains).

Methods inherited from class java.lang.Object

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

Constructor Detail

ArrayQueue

public ArrayQueue()

Initialize an empty queue with an initial capacity of 10. Note that the add method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

- - none

Postcondition:

This queue is empty and has an initial capacity of 10.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[10].

ArrayQueue

public ArrayQueue(int initialCapacity)

Initialize an empty queue with a specified initial capacity. Note that the add method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

initialCapacity - the initial capacity of this queue

Precondition:

initialCapacity is non-negative.

Postcondition:

This queue is empty and has the given initial capacity.

Throws:

java.lang.IllegalArgumentException - Indicates that initialCapacity is negative.

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[initialCapacity].

Method Detail

clone

public ArrayQueue<E> clone()

Generate a copy of this queue.

Overrides:

clone in class java.lang.Object

Parameters:

- - none

Returns:

The return value is a copy of this queue. Subsequent changes to the copy will not affect the original, nor vice versa. Note that the return value must be type cast to an ArrayQueue before it can be used.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for creating the clone.

add

public void add(E item)

Insert a new item in this queue. If the addition would take this queue beyond its current capacity, then the capacity is increased before adding the new item. The new item may be the null reference.

Parameters:

item - the item to be pushed onto this queue

Postcondition:

The item has been pushed onto this queue.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for increasing the queue's capacity.

Note:

An attempt to increase the capacity beyond Integer.MAX_VALUE will cause the queue to fail with an arithmetic overflow.

ensureCapacity

public void ensureCapacity(int minimumCapacity)

Change the current capacity of this queue.

Parameters:

minimumCapacity - the new capacity for this queue

Postcondition:

This queue's capacity has been changed to at least minimumCapacity. If the capacity was already at or greater than minimumCapacity, then the capacity is left unchanged.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[minimumCapacity].

getCapacity

public int getCapacity()

Accessor method to get the current capacity of this queue. The add method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

- - none

Returns:

the current capacity of this queue

isEmpty

public boolean isEmpty()

Determine whether this queue is empty.

Parameters:

- - none

Returns:

true if this queue is empty; false otherwise.

remove

public E remove()

Get the front item, removing it from this queue.

Parameters:

- - none

Precondition:

This queue is not empty.

Postcondition:

The return value is the front item of this queue, and the item has been removed.

Throws:

java.util.NoSuchElementException - Indicates that this queue is empty.

size

public int size()

Accessor method to determine the number of items in this queue.

Parameters:

- - none

Returns:

the number of items in this queue

trimToSize

public void trimToSize()

Reduce the current capacity of this queue to its actual size (i.e., the number of items it contains).

Parameters:

- - none

Postcondition:

This queue's capacity has been changed to its current size.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for altering the capacity.