1 | // Copyright 2012 Georg-August-Universität Göttingen, Germany
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2 | //
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3 | // Licensed under the Apache License, Version 2.0 (the "License");
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4 | // you may not use this file except in compliance with the License.
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5 | // You may obtain a copy of the License at
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6 | //
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7 | // http://www.apache.org/licenses/LICENSE-2.0
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8 | //
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9 | // Unless required by applicable law or agreed to in writing, software
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10 | // distributed under the License is distributed on an "AS IS" BASIS,
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11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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12 | // See the License for the specific language governing permissions and
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13 | // limitations under the License.
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14 |
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15 | package de.ugoe.cs.util.console;
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16 |
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17 | import java.io.IOException;
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18 | import java.io.ObjectInputStream;
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19 | import java.io.ObjectOutputStream;
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20 | import java.io.Serializable;
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21 | import java.util.Collection;
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22 | import java.util.HashMap;
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23 | import java.util.Map;
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24 |
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25 | /**
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26 | * <p>
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27 | * This data structure can be used by the commands to store any {@link Object}.
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28 | * The data is stored in a key-value map, with strings as keys.
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29 | * </p>
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30 | * <p>
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31 | * This class is implemented as a singleton, as more than one data container
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32 | * does not serves no purpose.
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33 | * </p>
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34 | *
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35 | * @author Steffen Herbold
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36 | * @version 1.0
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37 | */
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38 | public class GlobalDataContainer implements Serializable {
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39 |
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40 | /**
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41 | * <p>
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42 | * Id for object serialization.
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43 | * </p>
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44 | */
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45 | private static final long serialVersionUID = 1L;
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46 |
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47 | /**
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48 | * <p>
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49 | * Instance of the {@link GlobalDataContainer} (implemented as singleton).
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50 | * </p>
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51 | */
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52 | transient private static GlobalDataContainer theInstance = null;
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53 |
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54 | /**
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55 | * <p>
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56 | * Internal storage of the data.
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57 | * </p>
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58 | */
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59 | private Map<String, Object> dataObjects;
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60 |
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61 | /**
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62 | * <p>
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63 | * Returns the instance of the container. If it does not yet exist, the data
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64 | * container is created.
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65 | * </p>
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66 | *
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67 | * @return instance of the container
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68 | */
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69 | public static GlobalDataContainer getInstance() {
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70 | if (theInstance == null) {
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71 | theInstance = new GlobalDataContainer();
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72 | }
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73 | return theInstance;
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74 | }
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75 |
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76 | /**
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77 | * <p>
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78 | * Manual serialization of the object. Necessary to guarantee the singleton
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79 | * property.
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80 | * </p>
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81 | *
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82 | * @param s
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83 | * output stream for the serialization
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84 | * @throws IOException
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85 | * thrown if there is problem writing to the output stream
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86 | */
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87 | private void writeObject(ObjectOutputStream s) throws IOException {
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88 | s.defaultWriteObject();
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89 | s.writeObject(dataObjects);
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90 | }
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91 |
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92 | /**
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93 | * <p>
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94 | * Manual de-serialization of the object. Necessary to guarantee the
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95 | * singleton property.
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96 | *
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97 | * @param s
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98 | * input stream for the de-serialization
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99 | * @throws IOException
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100 | * thrown if there is problem reading from the input stream
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101 | * @throws ClassNotFoundException
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102 | * thrown if there is a problem reading from the input stream
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103 | */
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104 | @SuppressWarnings("unchecked")
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105 | private void readObject(ObjectInputStream s) throws IOException,
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106 | ClassNotFoundException {
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107 | s.defaultReadObject();
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108 | if (theInstance == null) {
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109 | theInstance = new GlobalDataContainer();
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110 | }
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111 | theInstance.dataObjects = (Map<String, Object>) s.readObject();
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112 | }
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113 |
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114 | /**
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115 | * <p>
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116 | * Manual de-serialization to guarantee the singleton property.
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117 | * </p>
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118 | *
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119 | * @return instance of the container
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120 | */
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121 | private Object readResolve() {
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122 | return theInstance;
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123 | }
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124 |
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125 | /**
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126 | * <p>
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127 | * Constructor. Creates a new GlobalDataContainer. Private to guarantee the
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128 | * singleton property.
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129 | * </p>
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130 | */
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131 | private GlobalDataContainer() {
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132 | dataObjects = new HashMap<String, Object>();
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133 | }
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134 |
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135 | /**
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136 | * <p>
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137 | * Adds data to the container.
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138 | * </p>
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139 | *
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140 | * @param key
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141 | * key that identifies the data
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142 | * @param data
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143 | * data that is stored
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144 | * @return true, if an old entry was overwritten; false otherwise
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145 | */
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146 | public boolean addData(String key, Object data) {
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147 | Object previousEntry = dataObjects.put(key, data);
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148 | return previousEntry != null;
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149 | }
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150 |
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151 | /**
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152 | * <p>
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153 | * Removes data from the container.
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154 | * </p>
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155 | *
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156 | * @param key
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157 | * key of the data to be removed
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158 | * @return true, if the object was removed; false if it was not present
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159 | */
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160 | public boolean removeData(String key) {
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161 | Object previousEntry = dataObjects.remove(key);
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162 | return previousEntry != null;
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163 | }
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164 |
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165 | /**
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166 | * <p>
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167 | * Returns the data associated with a key or {@code null} if no data is
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168 | * stored for the key.
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169 | * </p>
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170 | *
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171 | * @param key
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172 | * key whose data is returned
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173 | * @return data associated with the key; {@code null} if no data is
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174 | * available
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175 | */
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176 | public Object getData(String key) {
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177 | return dataObjects.get(key);
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178 | }
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179 |
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180 | /**
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181 | * <p>
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182 | * Resets the data container, i.e., deletes all its contents.
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183 | * </p>
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184 | */
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185 | public void reset() {
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186 | dataObjects = new HashMap<String, Object>();
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187 | }
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188 |
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189 | /**
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190 | * <p>
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191 | * Returns the keys of all objects contained in the storage.
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192 | * </p>
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193 | *
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194 | * @return keys of all objects in the storage
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195 | */
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196 | public Collection<String> getAllKeys() {
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197 | return dataObjects.keySet();
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198 | }
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199 |
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200 | }
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