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| org.apache.jcs.utils.struct.BoundedQueue |
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| 1 | package org.apache.jcs.utils.struct; |
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| 2 | ||
| 3 | /* |
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| 4 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 5 | * or more contributor license agreements. See the NOTICE file |
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| 6 | * distributed with this work for additional information |
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| 7 | * regarding copyright ownership. The ASF licenses this file |
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| 8 | * to you under the Apache License, Version 2.0 (the |
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| 9 | * "License"); you may not use this file except in compliance |
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| 10 | * with the License. You may obtain a copy of the License at |
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| 11 | * |
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| 12 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 13 | * |
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| 14 | * Unless required by applicable law or agreed to in writing, |
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| 15 | * software distributed under the License is distributed on an |
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| 16 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
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| 17 | * KIND, either express or implied. See the License for the |
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| 18 | * specific language governing permissions and limitations |
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| 19 | * under the License. |
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| 20 | */ |
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| 21 | ||
| 22 | /** |
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| 23 | * This is a bounded queue. It only allows maxSize items. |
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| 24 | * <p> |
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| 25 | * @author Aaron Smuts |
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| 26 | */ |
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| 27 | public class BoundedQueue |
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| 28 | { |
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| 29 | private int maxSize; |
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| 30 | ||
| 31 | 59 | private DoubleLinkedList list = new DoubleLinkedList(); |
| 32 | ||
| 33 | /** |
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| 34 | * Initialize the bounded queue. |
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| 35 | * <p> |
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| 36 | * @param maxSize |
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| 37 | */ |
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| 38 | 3 | public BoundedQueue( int maxSize ) |
| 39 | 56 | { |
| 40 | 59 | this.maxSize = maxSize; |
| 41 | 59 | } |
| 42 | ||
| 43 | /** |
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| 44 | * Adds an item to the end of the queue, which is the front of the list. |
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| 45 | * <p> |
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| 46 | * @param object |
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| 47 | */ |
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| 48 | public void add( Object object ) |
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| 49 | { |
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| 50 | 268 | if ( list.size() >= maxSize ) |
| 51 | { |
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| 52 | 80 | list.removeLast(); |
| 53 | } |
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| 54 | 268 | list.addFirst( new DoubleLinkedListNode( object ) ); |
| 55 | 268 | } |
| 56 | ||
| 57 | /** |
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| 58 | * Takes the last of the underlying double linked list. |
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| 59 | * <p> |
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| 60 | * @return null if it is epmpty. |
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| 61 | */ |
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| 62 | public Object take() |
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| 63 | { |
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| 64 | 116 | DoubleLinkedListNode node = list.removeLast(); |
| 65 | 116 | if ( node != null ) |
| 66 | { |
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| 67 | 108 | return node.getPayload(); |
| 68 | } |
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| 69 | 8 | return null; |
| 70 | } |
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| 71 | ||
| 72 | /** |
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| 73 | * Return the number of items in the queue. |
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| 74 | * <p> |
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| 75 | * @return size |
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| 76 | */ |
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| 77 | public int size() |
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| 78 | { |
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| 79 | 8 | return list.size(); |
| 80 | } |
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| 81 | ||
| 82 | /** |
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| 83 | * Return true if the size is <= 0; |
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| 84 | * <p> |
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| 85 | * @return true is size <= 0; |
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| 86 | */ |
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| 87 | public boolean isEmpty() |
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| 88 | { |
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| 89 | 63 | return list.size() <= 0; |
| 90 | } |
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| 91 | } |
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