com.hazelcast.util

Class QueueUtil

java.lang.Object

com.hazelcast.util.QueueUtil

public final class QueueUtil
extends Object

Utility class for Queues

Method Summary

Modifier and Type	Method and Description
static int	drainQueue(Queue<?> queue) Drains the provided queue by the size of the queue as it is known upfront draining.
static <E> int	drainQueue(Queue<E> queue, int elementsToDrain, Predicate<E> drainedCountFilter) Drains the provided queue by the count provided in elementsToDrain.
static <E> int	drainQueue(Queue<E> queue, Predicate<E> drainedCountFilter) Drains the provided queue by the size of the queue as it is known upfront draining.

Methods inherited from class java.lang.Object

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

Method Detail

drainQueue

public static int drainQueue(Queue<?> queue)

Drains the provided queue by the size of the queue as it is known upfront draining.

The rational for using this method is the same as for using Collection.clear(): to remove all the elements from the queue. There are two major differences to highlight:

1. This method doesn't guarantee that the queue is empty on return if it is written concurrently.
2. This method returns the number of drained elements, while Collection.clear() doesn't.

These points makes this method more applicable than Collection.clear() is in conditions where the queue is written concurrently without blocking the writer threads for the time of draining the queue and the caller needs to know the number of elements removed from the queue.

Parameters:

queue - The queue to be drained

Returns:

The number of elements drained from the queue

drainQueue

public static <E> int drainQueue(Queue<E> queue,
                                 Predicate<E> drainedCountFilter)

Drains the provided queue by the size of the queue as it is known upfront draining.

The rational for using this method is the same as for using Collection.clear(): to remove all the elements from the queue. There are two major differences to highlight:

1. This method doesn't guarantee that the queue is empty on return if it is written concurrently.
2. This method returns the number of drained elements, while Collection.clear() doesn't.

These points makes this method more applicable than Collection.clear() is in conditions where the queue is written concurrently without blocking the writer threads for the time of draining the queue and the caller needs to know the number of elements removed from the queue.

You may provide a predicate which will allow some elements to be drained but not be counted against the returned number of drained events.

Type Parameters:

E - the type of the elements in the queue

Parameters:

queue - The queue to be drained

drainedCountFilter - filter which determines if the drained element is counted against the returned count. The filter may be null in which case all elements match

Returns:

The number of elements drained from the queue which pass the given predicate

drainQueue

public static <E> int drainQueue(Queue<E> queue,
                                 int elementsToDrain,
                                 Predicate<E> drainedCountFilter)

Drains the provided queue by the count provided in elementsToDrain. You may provide a predicate which will allow some elements to be drained but not be counted against the returned number of drained events.

Type Parameters:

E - the type of the elements in the queue

Parameters:

queue - The queue to be drained

elementsToDrain - The number of elements to be drained from the queue

drainedCountFilter - filter which determines if the drained element is counted against the returned count. The filter may be null in which case all elements match

Returns:

The number of elements drained from the queue which pass the given predicate