001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections;
018
019import java.util.Collection;
020
021/**
022 * Defines a collection that allows objects to be removed in some well-defined order.
023 * <p>
024 * The removal order can be based on insertion order (eg, a FIFO queue or a
025 * LIFO stack), on access order (eg, an LRU cache), on some arbitrary comparator
026 * (eg, a priority queue) or on any other well-defined ordering.
027 * <p>
028 * Note that the removal order is not necessarily the same as the iteration
029 * order.  A <code>Buffer</code> implementation may have equivalent removal
030 * and iteration orders, but this is not required.
031 * <p>
032 * This interface does not specify any behavior for 
033 * {@link Object#equals(Object)} and {@link Object#hashCode} methods.  It
034 * is therefore possible for a <code>Buffer</code> implementation to also
035 * also implement {@link java.util.List}, {@link java.util.Set} or 
036 * {@link Bag}.
037 * <p>
038 * <strong>Note:</strong> this class should be bytecode-identical to the 
039 * version in commons collections. This is required to allow backwards 
040 * compability with both previous versions of BeanUtils and also allow 
041 * coexistance with both collections 2.1 and 3.0.
042 *
043 * @since Commons Collections 2.1
044 * @version $Revision: 555824 $ $Date: 2007-07-13 01:27:15 +0100 (Fri, 13 Jul 2007) $
045 * 
046 * @author Avalon
047 * @author Berin Loritsch
048 * @author Paul Jack
049 * @author Stephen Colebourne
050 */
051public interface Buffer extends Collection {
052
053    /**
054     * Gets and removes the next object from the buffer.
055     *
056     * @return the next object in the buffer, which is also removed
057     * @throws BufferUnderflowException if the buffer is already empty
058     */
059    Object remove();
060
061    /**
062     * Gets the next object from the buffer without removing it.
063     *
064     * @return the next object in the buffer, which is not removed
065     * @throws BufferUnderflowException if the buffer is empty
066     */
067    Object get();
068
069}