com.sun.grizzly.util.TransferQueue Maven / Gradle / Ivy
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2009-2010 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
* "Portions Copyright [year] [name of copyright owner]"
*
* Contributor(s):
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license." If you don't indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above. However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/
/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/licenses/publicdomain
*/
package com.sun.grizzly.util;
import java.util.concurrent.*;
/**
* A {@link BlockingQueue} in which producers may wait for consumers
* to receive elements. A {@code TransferQueue} may be useful for
* example in message passing applications in which producers
* sometimes (using method {@code transfer}) await receipt of
* elements by consumers invoking {@code take} or {@code poll},
* while at other times enqueue elements (via method {@code put})
* without waiting for receipt. Non-blocking and time-out versions of
* {@code tryTransfer} are also available. A TransferQueue may also
* be queried via {@code hasWaitingConsumer} whether there are any
* threads waiting for items, which is a converse analogy to a
* {@code peek} operation.
*
* Like any {@code BlockingQueue}, a {@code TransferQueue} may be
* capacity bounded. If so, an attempted {@code transfer} operation
* may initially block waiting for available space, and/or
* subsequently block waiting for reception by a consumer. Note that
* in a queue with zero capacity, such as {@link SynchronousQueue},
* {@code put} and {@code transfer} are effectively synonymous.
*
*
This interface is a member of the
*
* Java Collections Framework.
*
* @since 1.7
* @author Doug Lea
* @param the type of elements held in this collection
*/
public interface TransferQueue extends BlockingQueue {
/**
* Transfers the specified element if there exists a consumer
* already waiting to receive it, otherwise returning {@code false}
* without enqueuing the element.
*
* @param e the element to transfer
* @return {@code true} if the element was transferred, else
* {@code false}
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this queue
* @throws NullPointerException if the specified element is null
* @throws IllegalArgumentException if some property of the specified
* element prevents it from being added to this queue
*/
boolean tryTransfer(E e);
/**
* Inserts the specified element into this queue, waiting if
* necessary for space to become available and the element to be
* dequeued by a consumer invoking {@code take} or {@code poll}.
*
* @param e the element to transfer
* @throws InterruptedException if interrupted while waiting,
* in which case the element is not enqueued.
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this queue
* @throws NullPointerException if the specified element is null
* @throws IllegalArgumentException if some property of the specified
* element prevents it from being added to this queue
*/
void transfer(E e) throws InterruptedException;
/**
* Inserts the specified element into this queue, waiting up to
* the specified wait time if necessary for space to become
* available and the element to be dequeued by a consumer invoking
* {@code take} or {@code poll}.
*
* @param e the element to transfer
* @param timeout how long to wait before giving up, in units of
* {@code unit}
* @param unit a {@code TimeUnit} determining how to interpret the
* {@code timeout} parameter
* @return {@code true} if successful, or {@code false} if
* the specified waiting time elapses before completion,
* in which case the element is not enqueued.
* @throws InterruptedException if interrupted while waiting,
* in which case the element is not enqueued.
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this queue
* @throws NullPointerException if the specified element is null
* @throws IllegalArgumentException if some property of the specified
* element prevents it from being added to this queue
*/
boolean tryTransfer(E e, long timeout, TimeUnit unit)
throws InterruptedException;
/**
* Returns {@code true} if there is at least one consumer waiting
* to dequeue an element via {@code take} or {@code poll}.
* The return value represents a momentary state of affairs.
*
* @return {@code true} if there is at least one waiting consumer
*/
boolean hasWaitingConsumer();
/**
* Returns an estimate of the number of consumers waiting to
* dequeue elements via {@code take} or {@code poll}. The return
* value is an approximation of a momentary state of affairs, that
* may be inaccurate if consumers have completed or given up
* waiting. The value may be useful for monitoring and heuristics,
* but not for synchronization control. Implementations of this
* method are likely to be noticeably slower than those for
* {@link #hasWaitingConsumer}.
*
* @return the number of consumers waiting to dequeue elements
*/
int getWaitingConsumerCount();
}