org.jgroups.util

Class LinkedListQueue


public class LinkedListQueue
extends java.lang.Object

LinkedListQueue implementation based on java.util.Queue. Can be renamed to Queue.java and compiled if someone wants to use this implementation rather than the original Queue. However, a simple insertion and removal of 1 million objects into this queue shoed that it was ca. 15-20% slower than the original queue. We just include it in the JGroups distribution to maybe use it at a later point when it has become faster.

Author:
Bela Ban

Field Summary

protected static Log
log

Constructor Summary

LinkedListQueue()
creates an empty queue

Method Summary

void
add(Object obj)
adds an object to the tail of this queue If the queue has been closed with close(true) no exception will be thrown if the queue has not been flushed yet.
void
addAtHead(Object obj)
Adds a new object to the head of the queue basically (obj.equals(LinkedListQueue.remove(LinkedListQueue.add(obj)))) returns true If the queue has been closed with close(true) no exception will be thrown if the queue has not been flushed yet.
void
close(boolean flush_entries)
Marks the queues as closed.
boolean
closed()
returns true if the Queue has been closed however, this method will return false if the queue has been closed using the close(true) method and the last element has yet not been received.
Vector
getContents()
returns a vector with all the objects currently in the queue
Object
peek()
returns the first object on the queue, without removing it.
Object
peek(long timeout)
returns the first object on the queue, without removing it.
Object
remove()
Removes 1 element from head or blocks until next element has been added
Object
remove(long timeout)
Removes 1 element from the head.
void
removeElement(Object obj)
removes a specific object from the queue.
void
reset()
resets the queue.
int
size()
returns the number of objects that are currently in the queue
String
toString()
prints the size of the queue

Field Details

log

protected static Log log

Constructor Details

LinkedListQueue

public LinkedListQueue()
creates an empty queue

Method Details

add

public void add(Object obj)
            throws QueueClosedException
adds an object to the tail of this queue If the queue has been closed with close(true) no exception will be thrown if the queue has not been flushed yet.

Parameters:
obj - - the object to be added to the queue


addAtHead

public void addAtHead(Object obj)
            throws QueueClosedException
Adds a new object to the head of the queue basically (obj.equals(LinkedListQueue.remove(LinkedListQueue.add(obj)))) returns true If the queue has been closed with close(true) no exception will be thrown if the queue has not been flushed yet.

Parameters:
obj - - the object to be added to the queue


close

public void close(boolean flush_entries)
Marks the queues as closed. When an add or remove operation is attempted on a closed queue, an exception is thrown.

Parameters:
flush_entries - When true, a end-of-entries marker is added to the end of the queue. Entries may be added and removed, but when the end-of-entries marker is encountered, the queue is marked as closed. This allows to flush pending messages before closing the queue.


closed

public boolean closed()
returns true if the Queue has been closed however, this method will return false if the queue has been closed using the close(true) method and the last element has yet not been received.

Returns:
true if the queue has been closed


getContents

public Vector getContents()
returns a vector with all the objects currently in the queue


peek

public Object peek()
            throws QueueClosedException
returns the first object on the queue, without removing it. If the queue is empty this object blocks until the first queue object has been added

Returns:
the first object on the queue


peek

public Object peek(long timeout)
            throws QueueClosedException,
                   TimeoutException
returns the first object on the queue, without removing it. If the queue is empty this object blocks until the first queue object has been added or the operation times out

Parameters:
timeout - how long in milli seconds will this operation wait for an object to be added to the queue before it times out

Returns:
the first object on the queue


remove

public Object remove()
            throws QueueClosedException
Removes 1 element from head or blocks until next element has been added

Returns:
the first element to be taken of the queue


remove

public Object remove(long timeout)
            throws QueueClosedException,
                   TimeoutException
Removes 1 element from the head. If the queue is empty the operation will wait for timeout ms. if no object is added during the timeout time, a Timout exception is thrown

Parameters:
timeout - - the number of milli seconds this operation will wait before it times out

Returns:
the first object in the queue


removeElement

public void removeElement(Object obj)
            throws QueueClosedException
removes a specific object from the queue. the object is matched up using the Object.equals method.

Parameters:
obj - the actual object to be removed from the queue


reset

public void reset()
resets the queue. This operation removes all the objects in the queue and marks the queue open


size

public int size()
returns the number of objects that are currently in the queue


toString

public String toString()
prints the size of the queue


Copyright B) 2001,2002 www.jgroups.com . All Rights Reserved.