scranton.queue
Class QueueViaArrayCirc

java.lang.Object
  scranton.queue.QueueViaArrayCirc

All Implemented Interfaces:

Queue

public class QueueViaArrayCirc

extends java.lang.Object

implements Queue

Implements the Queue interface via compositon using an array (wraparound).

Field Summary

protected java.lang.Object[]	actual The array that contains the objects in the queue.
protected int	front The index to the array location that contains the front.
protected int	qSize The actual size of the queue

Constructor Summary

	QueueViaArrayCirc() Constructs an empty queue
(package private)	QueueViaArrayCirc(int size) Constructs an empty queue of the indicated size.

Method Summary

java.lang.Object	dequeue() Decrease the size of the queue by one by removing and returning reference to the object that was at the front of the queue.
private java.lang.Object[]	doubler(java.lang.Object[] oldArray) Method doubler doubles the sixe of the array containing the queue and copies the queue into the new array.
void	enqueue(java.lang.Object item) Increase the size of the queue by one by placing item as the rear of the queue.
Queue	factory()
java.lang.Object	frontOf() Queue does not change, returns the reference to the front object in the queue.
boolean	isEmpty() Queue does not change, returns true iff the queue is empty.
java.lang.String	toString() Returns a string representation of the queue.

Methods inherited from class java.lang.Object

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

Field Detail

actual

protected java.lang.Object[] actual

The array that contains the objects in the queue.

front

protected int front

The index to the array location that contains the front.

qSize

protected int qSize

The actual size of the queue

Constructor Detail

QueueViaArrayCirc

public QueueViaArrayCirc()

Constructs an empty queue

QueueViaArrayCirc

QueueViaArrayCirc(int size)

Constructs an empty queue of the indicated size.

Parameters:

size - Establishes the initial size of the array actual

Method Detail

isEmpty

public boolean isEmpty()

Description copied from interface: Queue

Queue does not change, returns true iff the queue is empty.

Specifications:

Q'=Q
Return Q==()

Specified by:

isEmpty in interface Queue

Returns:

boolean Q==().

See Also:

Queue.isEmpty()

frontOf

public java.lang.Object frontOf()

Description copied from interface: Queue

Queue does not change, returns the reference to the front object in the queue.

Specifications:

Q!=()Q'=Q
Return a₀

Specified by:

frontOf in interface Queue

Returns:

Object Front of Queue.

See Also:

Queue.frontOf()

enqueue

public void enqueue(java.lang.Object item)

Description copied from interface: Queue

Increase the size of the queue by one by placing item as the rear of the queue.

Specifications:

Q'=(Q, obj)

Specified by:

enqueue in interface Queue

Parameters:

item - The new rear of the queue

See Also:

Queue.enqueue(java.lang.Object)

dequeue

public java.lang.Object dequeue()

Description copied from interface: Queue

Decrease the size of the queue by one by removing and returning reference to the object that was at the front of the queue. Note: The queue cannot be empty.

Specifications:

Q!=()Q = (a₀, Q')
Return: a₀

Specified by:

dequeue in interface Queue

Returns:

Object Front of queue.

See Also:

Queue.dequeue()

doubler

private java.lang.Object[] doubler(java.lang.Object[] oldArray)

Method doubler doubles the sixe of the array containing the queue and copies the queue into the new array.

Parameters:

oldArray - The (filled) array containing the stack's objects

Returns:

Object[] A new array that is double the size.

toString

public java.lang.String toString()

Description copied from interface: Queue

Returns a string representation of the queue. The format of the representation is "FRONT[O_front\t...\tO_rear]REAR"

Specified by:

toString in interface Queue

factory

public Queue factory()