1 | /**
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2 | *#########################################################################
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3 | *
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4 | * A component of the Gatherer application, part of the Greenstone digital
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5 | * library suite from the New Zealand Digital Library Project at the
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6 | * University of Waikato, New Zealand.
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7 | *
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8 | * Author: John Thompson, Greenstone Digital Library, University of Waikato
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9 | *
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10 | * Copyright (C) 1999 New Zealand Digital Library Project
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11 | *
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12 | * This program is free software; you can redistribute it and/or modify
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13 | * it under the terms of the GNU General Public License as published by
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14 | * the Free Software Foundation; either version 2 of the License, or
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15 | * (at your option) any later version.
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16 | *
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17 | * This program is distributed in the hope that it will be useful,
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18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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20 | * GNU General Public License for more details.
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21 | *
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22 | * You should have received a copy of the GNU General Public License
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23 | * along with this program; if not, write to the Free Software
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24 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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25 | *########################################################################
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26 | */
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27 | package org.greenstone.gatherer.util;
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28 |
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29 | /**************************************************************************************
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30 | * Written: 20/08/02
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31 | * Revised:
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32 | **************************************************************************************/
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33 | import java.util.HashMap;
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34 | import java.util.Iterator;
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35 |
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36 | /** Provides a HashMap implementation that indexes by two keys. Perfect for the storage of metadata references based on their metadata element and assigned value.
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37 | * @author John Thompson, Greenstone Digital Library, University of Waikato
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38 | * @version 2.3
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39 | */
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40 | public class HashMap3D
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41 | extends HashMap {
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42 |
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43 | private int capacity = 4;
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44 |
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45 | private int size = 0;
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46 |
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47 | private Object last_key_one = null;
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48 | private Object last_key_two = null;
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49 | private Object last_value = null;
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50 |
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51 | /** Default constructor.
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52 | */
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53 | public HashMap3D() {
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54 | super();
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55 | }
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56 | /** Constructor with a specific initial capacity.
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57 | * @param capacity The initial capacity as an <i>int</i>.
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58 | */
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59 | public HashMap3D(int capacity) {
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60 | super(capacity);
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61 | this.capacity = capacity;
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62 | }
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63 | /** Completely remove the contents of this HashMap and its child HashMaps. */
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64 | public void clear() {
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65 | size = 0;
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66 | Iterator iterator = values().iterator();
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67 | while(iterator.hasNext()) {
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68 | HashMap inner_mapping = (HashMap) iterator.next();
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69 | inner_mapping.clear();
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70 | inner_mapping = null;
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71 | }
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72 | iterator = null;
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73 | super.clear();
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74 | }
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75 | /** Determine if this hash map contains an entry for the given keys. Also cache this entry because theres a good chance the next get call will ask for this entry.
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76 | * @param key_one The first key as an <strong>Object</strong>.
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77 | * @param key_two The second key as an <strong>Object</strong>.
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78 | * @return <i>true</i> if such an entry exists, <i>false</i> otherwise.
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79 | */
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80 | public boolean contains(Object key_one, Object key_two) {
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81 | boolean result = false;
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82 | // Retrieve the hash mapping at key_one.
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83 | HashMap map = (HashMap) get(key_one);
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84 | // If there is such a map then retrieve the value at key_two.
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85 | if(map != null) {
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86 | last_value = map.get(key_two);
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87 | if(last_value != null) {
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88 | last_key_one = key_one;
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89 | last_key_two = key_two;
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90 | result = true;
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91 | }
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92 | }
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93 | return result;
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94 | }
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95 |
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96 | /** Retrieve an entry from this three dimensional hash mapping.
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97 | * @param key_one The first key as an <strong>Object</strong>.
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98 | * @param key_two The second key as an <strong>Object</strong>.
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99 | * @return The value <strong>Object</strong> located at (key_one, key_two), or <i>null</i> if no such value.
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100 | */
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101 | public Object get(Object key_one, Object key_two) {
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102 | Object result = null;
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103 | if(key_one.equals(last_key_one) && key_two.equals(last_key_two)) {
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104 | result = last_value;
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105 | }
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106 | else {
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107 | // Retrieve the hash mapping at key_one.
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108 | HashMap map = (HashMap) get(key_one);
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109 | // If there is such a map then retrieve the value at key_two.
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110 | if(map != null) {
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111 | result = map.get(key_two);
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112 | if(result != null) {
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113 | last_key_one = key_one;
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114 | last_key_two = key_two;
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115 | last_value = result;
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116 | }
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117 | }
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118 | }
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119 | return result;
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120 | }
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121 |
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122 | /** Put an entry into this three dimensional hash mapping.
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123 | * @param key_one The first key, to store this value under, as an <strong>Object</strong>.
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124 | * @param key_two The second key, to store this value under, as an <strong>Object</strong>.
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125 | * @param value The value <strong>Object</strong> itself.
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126 | */
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127 | public void put(Object key_one, Object key_two, Object value) {
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128 | // Retrieve the hash mapping at key_one, or if none exists create one.
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129 | HashMap map = (HashMap) get(key_one);
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130 | if(map == null) {
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131 | map = new HashMap(capacity);
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132 | put(key_one, map);
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133 | }
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134 | // Now add the value to this mapping.
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135 | map.put(key_two, value);
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136 | size++;
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137 | }
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138 | }
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