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Java > Open Source Codes > org > apache > avalon > cornerstone > blocks > scheduler > PriorityQueue


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at
6  *
7  * http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
12  * implied.
13  *
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */

17
18 package org.apache.avalon.cornerstone.blocks.scheduler;
19
20 import java.util.NoSuchElementException JavaDoc;
21
22 /**
23  * Iterface for priority queues.
24  * This interface does not dictate whether it is min or max heap.
25  *
26  * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
27  * @version CVS $Revision: 1.1 $ $Date: 2004/03/16 12:49:52 $
28  * @since 4.0
29  */

30 public interface PriorityQueue
31 {
32     /**
33      * Clear all elements from queue.
34      */

35     void clear();
36
37     /**
38      * Test if queue is empty.
39      *
40      * @return true if queue is empty else false.
41      */

42     boolean isEmpty();
43
44     /**
45      * Insert an element into queue.
46      *
47      * @param element the element to be inserted
48      */

49     void insert( Object JavaDoc element );
50
51     /**
52      * Return element on top of heap but don't remove it.
53      *
54      * @return the element at top of heap
55      * @throws NoSuchElementException if isEmpty() == true
56      */

57     Object JavaDoc peek() throws NoSuchElementException JavaDoc;
58
59     /**
60      * Return element on top of heap and remove it.
61      *
62      * @return the element at top of heap
63      * @throws NoSuchElementException if isEmpty() == true
64      */

65     Object JavaDoc pop() throws NoSuchElementException JavaDoc;
66 }
67
68
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