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).

See Also:
Constant Field Values
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.

 

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