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1   /*
2    *  Copyright 2002-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package org.apache.commons.collections;
17  
18  import java.util.Collection;
19  
20  /**
21   * Defines a collection that allows objects to be removed in some well-defined order.
22   * <p>
23   * The removal order can be based on insertion order (eg, a FIFO queue or a
24   * LIFO stack), on access order (eg, an LRU cache), on some arbitrary comparator
25   * (eg, a priority queue) or on any other well-defined ordering.
26   * <p>
27   * Note that the removal order is not necessarily the same as the iteration
28   * order.  A <code>Buffer</code> implementation may have equivalent removal
29   * and iteration orders, but this is not required.
30   * <p>
31   * This interface does not specify any behavior for 
32   * {@link Object#equals(Object)} and {@link Object#hashCode} methods.  It
33   * is therefore possible for a <code>Buffer</code> implementation to also
34   * also implement {@link java.util.List}, {@link java.util.Set} or 
35   * {@link Bag}.
36   * <p>
37   * <strong>Note:</strong> this class should be bytecode-identical to the 
38   * version in commons collections. This is required to allow backwards 
39   * compability with both previous versions of BeanUtils and also allow 
40   * coexistance with both collections 2.1 and 3.0.
41   *
42   * @since Commons Collections 2.1
43   * @version $Revision: 1.1 $ $Date: 2004/05/10 19:50:28 $
44   * 
45   * @author Avalon
46   * @author Berin Loritsch
47   * @author Paul Jack
48   * @author Stephen Colebourne
49   */
50  public interface Buffer extends Collection {
51  
52      /**
53       * Gets and removes the next object from the buffer.
54       *
55       * @return the next object in the buffer, which is also removed
56       * @throws BufferUnderflowException if the buffer is already empty
57       */
58      Object remove();
59  
60      /**
61       * Gets the next object from the buffer without removing it.
62       *
63       * @return the next object in the buffer, which is not removed
64       * @throws BufferUnderflowException if the buffer is empty
65       */
66      Object get();
67  
68  }