[927] | 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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[667] | 15 | package de.ugoe.cs.util.console;
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[1] | 16 |
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[88] | 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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[187] | 21 | import java.util.Collection;
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[1] | 22 | import java.util.HashMap;
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| 23 | import java.util.Map;
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| 24 |
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[171] | 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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[88] | 38 | public class GlobalDataContainer implements Serializable {
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[171] | 39 |
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[88] | 40 | /**
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[171] | 41 | * <p>
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[88] | 42 | * Id for object serialization.
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[171] | 43 | * </p>
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[88] | 44 | */
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| 45 | private static final long serialVersionUID = 1L;
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| 46 |
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[171] | 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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[88] | 52 | transient private static GlobalDataContainer theInstance = null;
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[171] | 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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[1] | 59 | private Map<String, Object> dataObjects;
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[171] | 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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[1] | 69 | public static GlobalDataContainer getInstance() {
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[171] | 70 | if (theInstance == null) {
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[1] | 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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[171] | 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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[88] | 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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[171] | 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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[88] | 104 | @SuppressWarnings("unchecked")
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[171] | 105 | private void readObject(ObjectInputStream s) throws IOException,
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| 106 | ClassNotFoundException {
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[88] | 107 | s.defaultReadObject();
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[171] | 108 | if (theInstance == null) {
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[88] | 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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[171] | 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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[88] | 121 | private Object readResolve() {
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| 122 | return theInstance;
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| 123 | }
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[171] | 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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[1] | 131 | private GlobalDataContainer() {
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| 132 | dataObjects = new HashMap<String, Object>();
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| 133 | }
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[171] | 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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[1] | 146 | public boolean addData(String key, Object data) {
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| 147 | Object previousEntry = dataObjects.put(key, data);
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[171] | 148 | return previousEntry != null;
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[1] | 149 | }
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[171] | 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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[1] | 160 | public boolean removeData(String key) {
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| 161 | Object previousEntry = dataObjects.remove(key);
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[171] | 162 | return previousEntry != null;
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[1] | 163 | }
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[171] | 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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[1] | 176 | public Object getData(String key) {
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| 177 | return dataObjects.get(key);
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| 178 | }
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[171] | 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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[1] | 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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[187] | 189 | /**
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| 190 | * <p>
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[191] | 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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[1] | 200 | }
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