org.apache.jackrabbit.rmi.observation.Queue Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.jackrabbit.rmi.observation;
import java.util.LinkedList;
/**
* The Queue class is a very simple queue assuming that there is
* at least one consumer and potentially multiple producers. This class poses
* no restrictions on the size of the queue.
*/
public class Queue {
/** The linked list implementing the queue of data */
private final LinkedList queue;
/**
* Creates an instance of this queue.
*/
public Queue() {
queue = new LinkedList();
}
/**
* Appends the given object to the end of the queue.
*
* After appending the element, the queue is notified such that threads
* waiting to retrieve an element from the queue are woken up.
*
* @param object the object to be added
*/
public void put(Object object) {
synchronized (queue) {
queue.addLast(object);
queue.notifyAll();
}
}
/**
* Returns the first element from the queue. If the queue is currently empty
* the method waits at most the given number of milliseconds.
*
* @param timeout The maximum number of milliseconds to wait for an entry in
* the queue if the queue is empty. If zero, the method waits forever
* for an element.
*
* @return The first element of the queue or null if the method
* timed out waiting for an entry.
*
* @throws InterruptedException Is thrown if the current thread is
* interrupted while waiting for the queue to get at least one entry.
*/
public Object get(long timeout) throws InterruptedException {
synchronized (queue) {
// wait for data if the queue is empty
if (queue.isEmpty()) {
queue.wait(timeout);
}
// return null if queue is (still) empty
if (queue.isEmpty()) {
return null;
}
// return first if queue has content now
return queue.removeFirst();
}
}
}