1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.data.osm;
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3 |
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4 | import java.io.Serializable;
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5 | import java.util.AbstractMap;
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6 | import java.util.AbstractSet;
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7 | import java.util.ArrayList;
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8 | import java.util.Arrays;
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9 | import java.util.Collection;
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10 | import java.util.ConcurrentModificationException;
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11 | import java.util.Iterator;
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12 | import java.util.List;
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13 | import java.util.Map;
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14 | import java.util.NoSuchElementException;
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15 | import java.util.Objects;
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16 | import java.util.Set;
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17 |
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18 | /**
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19 | * This class provides a read/write map that uses the same format as {@link AbstractPrimitive#keys}.
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20 | * It offers good performance for few keys.
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21 | * It uses copy on write, so there cannot be a {@link ConcurrentModificationException} while iterating through it.
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22 | *
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23 | * @author Michael Zangl
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24 | */
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25 | public class TagMap extends AbstractMap<String, String> implements Serializable {
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26 | static final long serialVersionUID = 1;
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27 | /**
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28 | * We use this array every time we want to represent an empty map.
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29 | * This saves us the burden of checking for null every time but saves some object allocations.
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30 | */
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31 | private static final String[] EMPTY_TAGS = new String[0];
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32 |
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33 | /**
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34 | * An iterator that iterates over the tags in this map. The iterator always represents the state of the map when it was created.
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35 | * Further changes to the map won't change the tags that we iterate over but they also won't raise any exceptions.
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36 | * @author Michael Zangl
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37 | */
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38 | private static class TagEntryInterator implements Iterator<Entry<String, String>> {
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39 | /**
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40 | * The current state of the tags we iterate over.
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41 | */
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42 | private final String[] tags;
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43 | /**
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44 | * Current tag index. Always a multiple of 2.
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45 | */
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46 | private int currentIndex;
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47 |
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48 | /**
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49 | * Create a new {@link TagEntryInterator}
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50 | * @param tags The tags array. It is never changed but should also not be changed by you.
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51 | */
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52 | TagEntryInterator(String ... tags) {
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53 | super();
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54 | this.tags = tags;
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55 | }
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56 |
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57 | @Override
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58 | public boolean hasNext() {
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59 | return currentIndex < tags.length;
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60 | }
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61 |
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62 | @Override
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63 | public Entry<String, String> next() {
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64 | if (!hasNext()) {
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65 | throw new NoSuchElementException();
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66 | }
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67 |
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68 | Tag tag = new Tag(tags[currentIndex], tags[currentIndex + 1]);
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69 | currentIndex += 2;
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70 | return tag;
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71 | }
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72 |
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73 | @Override
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74 | public void remove() {
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75 | throw new UnsupportedOperationException();
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76 | }
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77 |
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78 | }
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79 |
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80 | /**
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81 | * This is the entry set of this map. It represents the state when it was created.
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82 | * @author Michael Zangl
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83 | */
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84 | private static class TagEntrySet extends AbstractSet<Entry<String, String>> {
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85 | private final String[] tags;
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86 |
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87 | /**
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88 | * Create a new {@link TagEntrySet}
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89 | * @param tags The tags array. It is never changed but should also not be changed by you.
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90 | */
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91 | TagEntrySet(String ... tags) {
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92 | super();
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93 | this.tags = tags;
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94 | }
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95 |
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96 | @Override
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97 | public Iterator<Entry<String, String>> iterator() {
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98 | return new TagEntryInterator(tags);
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99 | }
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100 |
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101 | @Override
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102 | public int size() {
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103 | return tags.length / 2;
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104 | }
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105 |
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106 | }
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107 |
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108 | /**
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109 | * The tags field. This field is guarded using RCU.
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110 | */
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111 | private volatile String[] tags;
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112 |
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113 | /**
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114 | * Creates a new, empty tag map.
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115 | */
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116 | public TagMap() {
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117 | this((String[]) null);
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118 | }
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119 |
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120 | /**
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121 | * Create a new tag map and load it from the other map.
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122 | * @param tags The map to load from.
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123 | * @since 10604
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124 | */
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125 | public TagMap(Map<String, String> tags) {
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126 | putAll(tags);
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127 | }
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128 |
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129 | /**
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130 | * Copy constructor.
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131 | * @param tagMap The map to copy from.
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132 | * @since 10604
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133 | */
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134 | public TagMap(TagMap tagMap) {
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135 | this(tagMap.tags);
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136 | }
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137 |
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138 | /**
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139 | * Creates a new read only tag map using a key/value/key/value/... array.
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140 | * <p>
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141 | * The array that is passed as parameter may not be modified after passing it to this map.
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142 | * @param tags The tags array. It is not modified by this map.
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143 | */
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144 | public TagMap(String ... tags) {
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145 | if (tags == null || tags.length == 0) {
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146 | this.tags = EMPTY_TAGS;
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147 | } else {
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148 | if (tags.length % 2 != 0) {
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149 | throw new IllegalArgumentException("tags array length needs to be multiple of two.");
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150 | }
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151 | this.tags = tags;
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152 | }
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153 | }
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154 |
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155 | /**
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156 | * Creates a new map using the given list of tags. For dupplicate keys the last value found is used.
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157 | * @param tags The tags
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158 | * @since 10736
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159 | */
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160 | public TagMap(Collection<Tag> tags) {
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161 | for (Tag tag : tags) {
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162 | put(tag.getKey(), tag.getValue());
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163 | }
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164 | }
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165 |
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166 | @Override
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167 | public Set<Entry<String, String>> entrySet() {
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168 | return new TagEntrySet(tags);
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169 | }
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170 |
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171 | @Override
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172 | public boolean containsKey(Object key) {
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173 | return indexOfKey(tags, key) >= 0;
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174 | }
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175 |
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176 | @Override
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177 | public String get(Object key) {
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178 | String[] tags = this.tags;
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179 | int index = indexOfKey(tags, key);
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180 | return index < 0 ? null : tags[index + 1];
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181 | }
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182 |
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183 | @Override
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184 | public boolean containsValue(Object value) {
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185 | String[] tags = this.tags;
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186 | for (int i = 1; i < tags.length; i += 2) {
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187 | if (value.equals(tags[i])) {
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188 | return true;
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189 | }
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190 | }
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191 | return false;
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192 | }
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193 |
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194 | @Override
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195 | public synchronized String put(String key, String value) {
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196 | Objects.requireNonNull(key);
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197 | Objects.requireNonNull(value);
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198 | int index = indexOfKey(tags, key);
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199 | int newTagArrayLength = tags.length;
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200 | if (index < 0) {
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201 | index = newTagArrayLength;
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202 | newTagArrayLength += 2;
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203 | }
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204 |
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205 | String[] newTags = Arrays.copyOf(tags, newTagArrayLength);
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206 | String old = newTags[index + 1];
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207 | newTags[index] = key;
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208 | newTags[index + 1] = value;
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209 | tags = newTags;
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210 | return old;
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211 | }
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212 |
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213 | @Override
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214 | public synchronized String remove(Object key) {
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215 | int index = indexOfKey(tags, key);
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216 | if (index < 0) {
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217 | return null;
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218 | }
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219 | String old = tags[index + 1];
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220 | int newLength = tags.length - 2;
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221 | if (newLength == 0) {
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222 | tags = EMPTY_TAGS;
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223 | } else {
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224 | String[] newTags = new String[newLength];
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225 | System.arraycopy(tags, 0, newTags, 0, index);
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226 | System.arraycopy(tags, index + 2, newTags, index, newLength - index);
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227 | tags = newTags;
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228 | }
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229 |
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230 | return old;
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231 | }
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232 |
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233 | @Override
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234 | public synchronized void clear() {
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235 | tags = EMPTY_TAGS;
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236 | }
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237 |
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238 | @Override
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239 | public int size() {
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240 | return tags.length / 2;
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241 | }
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242 |
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243 | /**
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244 | * Gets a list of all tags contained in this map.
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245 | * @return The list of tags in the order they were added.
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246 | * @since 10604
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247 | */
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248 | public List<Tag> getTags() {
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249 | List<Tag> tagList = new ArrayList<>();
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250 | for (int i = 0; i < tags.length; i += 2) {
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251 | tagList.add(new Tag(tags[i], tags[i+1]));
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252 | }
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253 | return tagList;
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254 | }
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255 |
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256 | /**
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257 | * Finds a key in an array that is structured like the {@link #tags} array and returns the position.
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258 | * <p>
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259 | * We allow the parameter to be passed to allow for better synchronization.
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260 | *
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261 | * @param tags The tags array to search through.
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262 | * @param key The key to search.
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263 | * @return The index of the key (a multiple of two) or -1 if it was not found.
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264 | */
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265 | private static int indexOfKey(String[] tags, Object key) {
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266 | for (int i = 0; i < tags.length; i += 2) {
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267 | if (tags[i].equals(key)) {
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268 | return i;
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269 | }
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270 | }
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271 | return -1;
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272 | }
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273 |
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274 | @Override
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275 | public String toString() {
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276 | StringBuilder stringBuilder = new StringBuilder();
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277 | stringBuilder.append("TagMap[");
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278 | boolean first = true;
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279 | for (Map.Entry<String, String> e : entrySet()) {
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280 | if (!first) {
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281 | stringBuilder.append(',');
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282 | }
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283 | stringBuilder.append(e.getKey());
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284 | stringBuilder.append('=');
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285 | stringBuilder.append(e.getValue());
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286 | first = false;
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287 | }
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288 | stringBuilder.append(']');
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289 | return stringBuilder.toString();
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290 | }
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291 |
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292 | /**
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293 | * Gets the backing tags array. Do not modify this array.
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294 | * @return The tags array.
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295 | */
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296 | String[] getTagsArray() {
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297 | return tags;
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298 | }
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299 | }
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