com.ibm.ras
Class RASCircularQueue

java.lang.Object
  |
  +--com.ibm.ras.RASCircularQueue

All Implemented Interfaces:

RASIQueue

public class RASCircularQueue

extends java.lang.Object

implements RASIQueue

RASCircularQueue is a circular queue for RAS events. When the queue fills, the next RAS event replaces the oldest event already in the queue.

See Also:

RASIQueue, RASQueue

Field Summary

static int

DEFAULT_QUEUE_SIZE The default queue size (10,000).

Constructor Summary

RASCircularQueue()
Creates a RASCircularQueue, whose size is defined by DEFAULT_QUEUE_SIZE.

RASCircularQueue(int size)
Creates a RASCircularQueue.

Method Summary

java.lang.Object	dequeue() Removes an object from the beginning of the queue.
void	enqueue(java.lang.Object object) Adds an object to the end of the queue.
java.lang.Object	firstObject() Returns the first object on the queue, but does not remove it from the queue.
int	getMaximumQueueSize() Gets the maximum number of objects which this queue will hold.
int	getQueueSize() Gets the current number of objects in this queue.
boolean	isCircular() Determines if the queue is circular.
boolean	isEmpty() Determines if the queue is empty.
boolean	isFull() Determines if the queue is full.
void	requeue(java.lang.Object object) Returns an object to the front of the queue.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_QUEUE_SIZE

public static final int DEFAULT_QUEUE_SIZE

The default queue size (10,000).

Constructor Detail

RASCircularQueue

public RASCircularQueue()

Creates a RASCircularQueue, whose size is defined by DEFAULT_QUEUE_SIZE.

RASCircularQueue

public RASCircularQueue(int size)
                 throws java.lang.IllegalArgumentException

Creates a RASCircularQueue.

Parameters:

size - The number of objects that this queue can hold. If the size is zero, the queue size is set to DEFAULT_QUEUE_SIZE.

Throws:

java.lang.IllegalArgumentException - This exception is thrown if the size parameter is less than zero.

Method Detail

getQueueSize

public int getQueueSize()

Gets the current number of objects in this queue.

Specified by:

getQueueSize in interface RASIQueue

Returns:

The current queue size.

getMaximumQueueSize

public int getMaximumQueueSize()

Gets the maximum number of objects which this queue will hold.

Specified by:

getMaximumQueueSize in interface RASIQueue

Returns:

The maximum queue size.

isEmpty

public boolean isEmpty()

Determines if the queue is empty.

Specified by:

isEmpty in interface RASIQueue

Returns:

true if the queue is empty or false otherwise.

isFull

public boolean isFull()

Determines if the queue is full.

Specified by:

isFull in interface RASIQueue

Returns:

true if the queue is full or false otherwise. (This queue always returns false.)

isCircular

public boolean isCircular()

Determines if the queue is circular. A circular queue always accepts new objects. If all slots are full, a new object replaces the oldest object in the queue.

Specified by:

isCircular in interface RASIQueue

Returns:

true if this queue is circular, or false otherwise. (This queue always returns true.)

enqueue

public void enqueue(java.lang.Object object)
             throws RASQueueFullException

Adds an object to the end of the queue. If the object is null, nothing is enqueued.

Specified by:

enqueue in interface RASIQueue

Parameters:

object - The object to be placed on the queue.

Throws:

RASQueueFullException - This exception is thrown if the queue is full.

dequeue

public java.lang.Object dequeue()
                         throws RASQueueEmptyException

Removes an object from the beginning of the queue.

Specified by:

dequeue in interface RASIQueue

Returns:

The first object in the queue.

Throws:

RASQueueEmptyException - This exception is thrown if the queue is empty.

requeue

public void requeue(java.lang.Object object)
             throws java.lang.IllegalStateException

Returns an object to the front of the queue. If the object is null, nothing is enqueued.

Specified by:

requeue in interface RASIQueue

Parameters:

object - The object to be placed on the queue.

Throws:

java.lang.IllegalStateException - This exception is always thrown because there is no way to reliably add an object to the beginning of a circular queue if objects are added and removed via enqueue and dequeue. See RASQueue.requeue.

firstObject

public java.lang.Object firstObject()
                             throws RASQueueEmptyException

Returns the first object on the queue, but does not remove it from the queue.

Specified by:

firstObject in interface RASIQueue

Returns:

The first object in the queue.

Throws:

RASQueueEmptyException - This exception is thrown if the queue is empty.