com.hazelcast.internal.util.QueueUtil Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2023, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.internal.util;
import java.util.Queue;
import java.util.function.Predicate;
/**
* Utility class for Queues
*/
public final class QueueUtil {
private QueueUtil() {
}
/**
* 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
* {@link Queue#clear()}: to remove all the elements from the queue.
* There are two major differences to highlight:
*
* - This method doesn't guarantee that the queue is empty on
* return if it is written concurrently.
* - This method returns the number of drained elements, while
* {@link Queue#clear()} doesn't.
*
*
* These points makes this method more applicable than
* {@link Queue#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.
*
* @param queue The queue to be drained
* @return The number of elements drained from the queue
*/
public static int drainQueue(Queue queue) {
return drainQueue(queue, queue.size(), null);
}
/**
* 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
* {@link Queue#clear()}: to remove all the elements from the queue.
* There are two major differences to highlight:
*
* - This method doesn't guarantee that the queue is empty on
* return if it is written concurrently.
* - This method returns the number of drained elements, while
* {@link Queue#clear()} doesn't.
*
*
* These points makes this method more applicable than
* {@link Queue#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.
*
* @param queue The queue to be drained
* @param drainedCountFilter filter which determines if the drained element
* is counted against the returned count. The filter
* may be {@code null} in which case all elements
* match
* @param the type of the elements in the queue
* @return The number of elements drained from the queue which pass the
* given predicate
*/
public static int drainQueue(Queue queue, Predicate drainedCountFilter) {
return drainQueue(queue, queue.size(), drainedCountFilter);
}
/**
* Drains the provided queue by the count provided in {@code 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.
*
* @param queue The queue to be drained
* @param elementsToDrain The number of elements to be drained from
* the queue
* @param drainedCountFilter filter which determines if the drained element
* is counted against the returned count. The filter
* may be {@code null} in which case all elements
* match
* @param the type of the elements in the queue
* @return The number of elements drained from the queue which pass the
* given predicate
*/
public static int drainQueue(Queue queue,
int elementsToDrain,
Predicate drainedCountFilter) {
int drained = 0;
boolean drainMore = true;
for (int i = 0; i < elementsToDrain && drainMore; i++) {
E polled = queue.poll();
if (polled != null) {
if (drainedCountFilter == null || drainedCountFilter.test(polled)) {
drained++;
}
} else {
drainMore = false;
}
}
return drained;
}
}