org.opennms.core.queue

Class FifoQueueImpl<T>

java.lang.Object

org.opennms.core.queue.FifoQueueImpl<T>

All Implemented Interfaces:

FifoQueue<T>

Direct Known Subclasses:

LegacyScheduler.PeekableFifoQueue, Scheduler.PeekableFifoQueue

public class FifoQueueImpl<T>
extends Object
implements FifoQueue<T>

This interface defines a queue that uses F irst In, F irst O ut semantics when adding and removing objects. Each object that is added to the queue is effectively placed at the end of the list of previous elements. Each call to remove will result in the removal of the next element, or the oldest element in the queue.

Author:

Brian Weaver

Field Summary

Fields

Modifier and Type	Field and Description
protected BlockingQueue<T>	m_delegate The delegate list where queue elements are stored.

Constructor Summary

Constructors

Constructor and Description
FifoQueueImpl() Constructs a new First In, First Out queue that can be used to exchange data.

Method Summary

Methods

Modifier and Type	Method and Description
void	add(T element) Inserts a new element into the queue.
boolean	add(T element, long timeout) Inserts a new element into the queue.
boolean	isEmpty() Used to test if the current queue has no stored elements.
T	remove() Removes the oldest element from the queue.
T	remove(long timeout) Removes the next element from the queue if one becomes available before the timeout expires.
int	size() Returns the current number of elements that are in the queue.

Methods inherited from class java.lang.Object

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

Field Detail

m_delegate

protected final BlockingQueue<T> m_delegate

The delegate list where queue elements are stored. The elements are removed from the front of the list and added to the end of the list, always!

Constructor Detail

FifoQueueImpl

public FifoQueueImpl()

Constructs a new First In, First Out queue that can be used to exchange data. The implementation is thread safe and can be used to exchange data between to concurrent processes.

Method Detail

add

public void add(T element)
         throws InterruptedException

Inserts a new element into the queue.

Specified by:

add in interface FifoQueue<T>

Parameters:

element - The object to append to the queue.

Throws:

FifoQueueException - if any.

InterruptedException - if any.

add

public boolean add(T element,
          long timeout)
            throws InterruptedException

Inserts a new element into the queue. If the queue has reached an implementation limit and the timeout expires, then a false value is returned to the caller. Inserts a new element into the queue. If the queue has reached an implementation limit and the timeout expires, then a false value is returned to the caller.

Specified by:

add in interface FifoQueue<T>

Parameters:

element - The object to append to the queue.

timeout - The time to wait on the insertion to succeed.

Returns:

True if the element was successfully added to the queue before the timeout expired, false otherwise.

Throws:

InterruptedException - Thrown if the thread is interrupted.

remove

public T remove()
         throws InterruptedException

Removes the oldest element from the queue.

Specified by:

remove in interface FifoQueue<T>

Returns:

The oldest object in the queue.

Throws:

FifoQueueException - if any.

InterruptedException - if any.

remove

public T remove(long timeout)
         throws InterruptedException

Removes the next element from the queue if one becomes available before the timeout expires. If the timeout expires before an element is available then a null reference is returned to the caller. Removes the next element from the queue if one becomes available before the timeout expires. If the timeout expires before an element is available then a null reference is returned to the caller.

Specified by:

remove in interface FifoQueue<T>

Parameters:

timeout - The time to wait on an object to be available.

Returns:

The oldest object in the queue, or null if one is not available.

Throws:

FifoQueueException - Thrown if a queue error occurs.

InterruptedException - Thrown if the thread is interrupted.

size

public int size()

Returns the current number of elements that are in the queue.

Specified by:

size in interface FifoQueue<T>

Returns:

The number of elements in the queue.

isEmpty

public boolean isEmpty()

Used to test if the current queue has no stored elements.

Specified by:

isEmpty in interface FifoQueue<T>

Returns:

True if the queue is empty.