01 /*
02 * Licensed to the Apache Software Foundation (ASF) under one
03 * or more contributor license agreements. See the NOTICE file
04 * distributed with this work for additional information
05 * regarding copyright ownership. The ASF licenses this file
06 * to you under the Apache License, Version 2.0 (the
07 * "License"); you may not use this file except in compliance
08 * with the License. You may obtain a copy of the License at
09 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 *
20 */
21 package org.apache.qpid.util;
22
23 import java.util.Queue;
24
25 /**
26 * Defines a queue that has a push operation to add an element to the head of the queue.
27 *
28 * @todo Seems like this may be pointless, the implementation uses this method to increment the message count
29 * then calls offer. Why not simply override offer and drop this interface?
30 */
31 public interface MessageQueue<E> extends Queue<E>
32 {
33 /**
34 * Inserts the specified element into this queue, if possible. When using queues that may impose insertion
35 * restrictions (for example capacity bounds), method offer is generally preferable to method Collection.add(E),
36 * which can fail to insert an element only by throwing an exception.
37 *
38 * @param o The element to insert.
39 *
40 * @return <tt>true</tt> if it was possible to add the element to this queue, else <tt>false</tt>
41 */
42 boolean pushHead(E o);
43 }
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