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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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