com.portal.common

Class ProducerConsumerQueue

java.lang.Object

com.portal.common.ProducerConsumerQueue

public class ProducerConsumerQueue
extends Object

An implementation of a ProducerConsumerQueue - often used to pass messages and data between threads

Version:

%version: 1 % %date_modified: Tue Jul 20 21:33:24 1999 %

Author:

larrylf

Constructor Summary

Constructors

Constructor and Description
ProducerConsumerQueue() Create a new instance of a PC Queue

Method Summary

Modifier and Type	Method and Description
void	addFirst(Object o) Add a new object to the queue (Produce).
void	addPriority(Object o) Add a new object to the queue giving it priorty.
boolean	hasWaiters() Returns true if there are Consumer threads waiting for objects.
Object	removeLast() Remove an object from the queue (Consume).
Object	removeLast(long maxTime) Remove an object from the queue (Consume).
int	size() Returns the number of objects on the PCQueue.

Methods inherited from class java.lang.Object

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

Constructor Detail

ProducerConsumerQueue

public ProducerConsumerQueue()

Create a new instance of a PC Queue

Method Detail

addFirst

public void addFirst(Object o)

Add a new object to the queue (Produce). PCQueues follow Quque (FIFO) symantics, so new items are added to one end, and removed from the other. If one or more Consumer threads are waiting, one will be notified.

Parameters:

o - Object to add to the queue

addPriority

public void addPriority(Object o)

Add a new object to the queue giving it priorty. This will be the next object fetched by a Consumer unless another priority object is produced before one is consumed. Priority objects follow Stack symantics (FILO), and all priority items will be consumed before non-priority objects If one or more Consumer threads are waiting, one will be notified.

Parameters:

o - Object to add to the queue

removeLast

public Object removeLast()

Remove an object from the queue (Consume). If the queue is empty, the calling thread will block until an object is available before returning.

Returns:

An object from the queue.

removeLast

public Object removeLast(long maxTime)

Remove an object from the queue (Consume). If the queue is empty, the calling thread will block until an object is available or until the specified time passes before returning. Null will be returned if a timeout occures.

Parameters:

maxTime - THe maximum time to wait for an Object in milliseconds

Returns:

An object from the queue.

hasWaiters

public boolean hasWaiters()

Returns true if there are Consumer threads waiting for objects.

Returns:

true if there are waiting consumers

size

public int size()

Returns the number of objects on the PCQueue. Subject to race conditions

Returns:

The number of object on the PCQueue