[13] | 1 | package de.ugoe.cs.eventbench.models;
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[1] | 2 |
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[86] | 3 | import java.io.Serializable;
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[1] | 4 | import java.security.InvalidParameterException;
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[102] | 5 | import java.util.Collection;
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[1] | 6 | import java.util.LinkedList;
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| 7 | import java.util.List;
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[129] | 8 | import java.util.Set;
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[1] | 9 |
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[13] | 10 | import de.ugoe.cs.eventbench.models.Trie.Edge;
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| 11 | import de.ugoe.cs.eventbench.models.Trie.TrieVertex;
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[1] | 12 | import de.ugoe.cs.util.StringTools;
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[5] | 13 | import edu.uci.ics.jung.graph.DelegateTree;
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[106] | 14 | import edu.uci.ics.jung.graph.Tree;
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[1] | 15 |
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[106] | 16 | /**
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| 17 | * <p>
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| 18 | * This class implements a node of a trie. Each node is associated with a symbol
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| 19 | * and has a counter. The counter marks the number of occurences of the sequence
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| 20 | * defined by the path from the root of the trie to this node.
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| 21 | * </p>
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| 22 | *
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| 23 | * @author Steffen Herbold
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| 24 | *
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| 25 | * @param <T>
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| 26 | * Type of the symbols that are stored in the trie.
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| 27 | * @see Trie
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| 28 | */
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| 29 | class TrieNode<T> implements Serializable {
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[1] | 30 |
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[86] | 31 | /**
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[106] | 32 | * <p>
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[86] | 33 | * Id for object serialization.
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[106] | 34 | * </p>
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[86] | 35 | */
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| 36 | private static final long serialVersionUID = 1L;
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[106] | 37 |
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| 38 | /**
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| 39 | * <p>
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| 40 | * Counter for the number of occurences of the sequence.
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| 41 | * </p>
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| 42 | */
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[1] | 43 | private int count;
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[106] | 44 |
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| 45 | /**
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| 46 | * <p>
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| 47 | * Symbol associated with the node.
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| 48 | * </p>
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| 49 | */
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[1] | 50 | private final T symbol;
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[106] | 51 |
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| 52 | /**
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| 53 | * <p>
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| 54 | * Child nodes of this node. If the node is a leaf this collection is empty.
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| 55 | * </p>
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| 56 | */
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[102] | 57 | private Collection<TrieNode<T>> children;
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[106] | 58 |
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| 59 | /**
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| 60 | * <p>
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| 61 | * Constructor. Creates a new TrieNode without a symbol associated.<br>
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| 62 | * <b>This constructor should only be used to create the root node of the
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| 63 | * trie!</b>
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| 64 | * </p>
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| 65 | */
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[6] | 66 | TrieNode() {
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| 67 | this.symbol = null;
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| 68 | count = 0;
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| 69 | children = new LinkedList<TrieNode<T>>();
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| 70 | }
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[106] | 71 |
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| 72 | /**
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| 73 | * <p>
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| 74 | * Constructor. Creates a new TrieNode. The symbol must not be null.
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| 75 | * </p>
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| 76 | *
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| 77 | * @param symbol
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| 78 | * symbol associated with the trie node
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| 79 | */
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[1] | 80 | public TrieNode(T symbol) {
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[106] | 81 | if (symbol == null) {
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| 82 | throw new InvalidParameterException(
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| 83 | "symbol must not be null. null is reserved for root node!");
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[1] | 84 | }
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| 85 | this.symbol = symbol;
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| 86 | count = 0;
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| 87 | children = new LinkedList<TrieNode<T>>();
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| 88 | }
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| 89 |
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[106] | 90 | /**
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| 91 | * <p>
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| 92 | * Adds a given subsequence to the trie and increases the counters
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| 93 | * accordingly.
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| 94 | * </p>
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| 95 | *
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| 96 | * @param subsequence
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| 97 | * subsequence whose counters are increased
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| 98 | * @see Trie#add(List)
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| 99 | */
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[1] | 100 | public void add(List<T> subsequence) {
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[106] | 101 | if (!subsequence.isEmpty()) {
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| 102 | if (!symbol.equals(subsequence.get(0))) { // should be guaranteed by
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| 103 | // the
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| 104 | // recursion/TrieRoot!
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[1] | 105 | throw new AssertionError("Invalid trie operation!");
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| 106 | }
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| 107 | count++;
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| 108 | subsequence.remove(0);
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[106] | 109 | if (!subsequence.isEmpty()) {
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[1] | 110 | T nextSymbol = subsequence.get(0);
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| 111 | getChildCreate(nextSymbol).add(subsequence);
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| 112 | }
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| 113 | }
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| 114 | }
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[106] | 115 |
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| 116 | /**
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| 117 | * <p>
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| 118 | * Returns the symbol associated with the node.
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| 119 | * </p>
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| 120 | *
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| 121 | * @return symbol associated with the node
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| 122 | */
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[1] | 123 | public T getSymbol() {
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| 124 | return symbol;
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| 125 | }
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[106] | 126 |
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| 127 | /**
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| 128 | * <p>
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| 129 | * Returns the number of occurences of the sequence represented by the node.
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| 130 | * </p>
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| 131 | *
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| 132 | * @return number of occurences of the sequence represented by the node
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| 133 | */
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[1] | 134 | public int getCount() {
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| 135 | return count;
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| 136 | }
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[106] | 137 |
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| 138 | /**
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| 139 | * <p>
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| 140 | * Returns the child of the node associated with the given symbol or creates
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| 141 | * it if it does not exist yet.
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| 142 | * </p>
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| 143 | *
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| 144 | * @param symbol
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| 145 | * symbol whose node is required
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| 146 | * @return node associated with the symbol
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| 147 | * @see Trie#getChildCreate(Object)
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| 148 | */
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| 149 | protected TrieNode<T> getChildCreate(T symbol) {
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[1] | 150 | TrieNode<T> node = getChild(symbol);
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[106] | 151 | if (node == null) {
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[1] | 152 | node = new TrieNode<T>(symbol);
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| 153 | children.add(node);
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| 154 | }
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| 155 | return node;
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| 156 | }
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[106] | 157 |
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| 158 | /**
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| 159 | * <p>
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| 160 | * Returns the child of the node associated with the given symbol or null if
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| 161 | * it does not exist.
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| 162 | * </p>
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| 163 | *
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| 164 | * @param symbol
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| 165 | * symbol whose node is required
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| 166 | * @return node associated with the symbol; null if no such node exists
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| 167 | * @see Trie#getChild(Object)
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| 168 | */
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[1] | 169 | protected TrieNode<T> getChild(T symbol) {
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[106] | 170 | for (TrieNode<T> child : children) {
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| 171 | if (child.getSymbol().equals(symbol)) {
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[1] | 172 | return child;
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| 173 | }
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| 174 | }
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| 175 | return null;
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| 176 | }
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| 177 |
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[106] | 178 | /**
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| 179 | * <p>
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[258] | 180 | * Returns all children of this node.
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| 181 | * </p>
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| 182 | *
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| 183 | * @return children of this node
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| 184 | */
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| 185 | protected Collection<TrieNode<T>> getChildren() {
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| 186 | return children;
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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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[106] | 191 | * Searches the sub-trie of this trie node for a given sequence and returns
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| 192 | * the node associated with the sequence or null if no such node is found.
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| 193 | * </p>
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| 194 | *
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| 195 | * @param sequence
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| 196 | * sequence that is searched for
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| 197 | * @return node associated with the sequence
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| 198 | * @see Trie#find(List)
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| 199 | */
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[1] | 200 | public TrieNode<T> find(List<T> subsequence) {
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| 201 | TrieNode<T> result = null;
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[106] | 202 | if (subsequence.isEmpty()) {
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[1] | 203 | result = this;
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| 204 | } else {
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| 205 | TrieNode<T> node = getChild(subsequence.get(0));
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[106] | 206 | if (node != null) {
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[1] | 207 | subsequence.remove(0);
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| 208 | result = node.find(subsequence);
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| 209 | }
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| 210 | }
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| 211 | return result;
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| 212 | }
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[106] | 213 |
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| 214 | /**
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| 215 | * <p>
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| 216 | * Returns a collection of all symbols that follow a this node, i.e., the
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| 217 | * symbols associated with the children of this node.
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| 218 | * </p>
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| 219 | *
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| 220 | * @return symbols follow this node
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| 221 | * @see TrieNode#getFollowingSymbols()
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| 222 | */
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[102] | 223 | public Collection<T> getFollowingSymbols() {
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| 224 | Collection<T> followingSymbols = new LinkedList<T>();
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[106] | 225 | for (TrieNode<T> child : children) {
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[1] | 226 | followingSymbols.add(child.getSymbol());
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| 227 | }
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| 228 | return followingSymbols;
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| 229 | }
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[106] | 230 |
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| 231 | /**
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| 232 | * <p>
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| 233 | * The string representation of a node is {@code symbol.toString()#count}
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| 234 | * </p>
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| 235 | *
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| 236 | * @see java.lang.Object#toString()
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| 237 | */
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[1] | 238 | @Override
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| 239 | public String toString() {
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[106] | 240 | String str = symbol.toString() + " #" + count;
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| 241 | if (!children.isEmpty()) {
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[1] | 242 | str += StringTools.ENDLINE + children.toString();
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| 243 | }
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[106] | 244 | return str;
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[1] | 245 | }
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| 246 |
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[106] | 247 | /**
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| 248 | * <p>
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| 249 | * Generates a {@link Tree} represenation of the trie.
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| 250 | * </p>
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| 251 | *
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| 252 | * @param parent
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| 253 | * parent vertex in the generated tree
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| 254 | * @param graph
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| 255 | * complete tree
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| 256 | */
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| 257 | void getGraph(TrieVertex parent, DelegateTree<TrieVertex, Edge> graph) {
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[6] | 258 | TrieVertex currentVertex;
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[251] | 259 | if (isRoot()) {
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[6] | 260 | currentVertex = new TrieVertex("root");
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| 261 | graph.addVertex(currentVertex);
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| 262 | } else {
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[106] | 263 | currentVertex = new TrieVertex(getSymbol().toString() + "#"
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| 264 | + getCount());
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| 265 | graph.addChild(new Edge(), parent, currentVertex);
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[6] | 266 | }
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[106] | 267 | for (TrieNode<T> node : children) {
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[6] | 268 | node.getGraph(currentVertex, graph);
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[106] | 269 | }
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[5] | 270 | }
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[106] | 271 |
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| 272 | /**
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| 273 | * <p>
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| 274 | * Appends the current node to the dot representation of the trie.
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| 275 | * </p>
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| 276 | *
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| 277 | * @param stringBuilder
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| 278 | * {@link StringBuilder} to which the dot representation is
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| 279 | * appended
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| 280 | */
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[30] | 281 | void appendDotRepresentation(StringBuilder stringBuilder) {
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| 282 | String thisSaneId;
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[251] | 283 | if (isRoot()) {
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[30] | 284 | thisSaneId = "root";
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| 285 | } else {
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[106] | 286 | thisSaneId = symbol.toString().replace("\"", "\\\"")
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| 287 | .replaceAll("[\r\n]", "")
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| 288 | + "#" + count;
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[30] | 289 | }
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[106] | 290 | stringBuilder.append(" " + hashCode() + " [label=\"" + thisSaneId
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| 291 | + "\"];" + StringTools.ENDLINE);
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| 292 | for (TrieNode<T> childNode : children) {
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| 293 | stringBuilder.append(" " + hashCode() + " -> "
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| 294 | + childNode.hashCode() + ";" + StringTools.ENDLINE);
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[30] | 295 | }
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[106] | 296 | for (TrieNode<T> childNode : children) {
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[30] | 297 | childNode.appendDotRepresentation(stringBuilder);
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| 298 | }
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| 299 | }
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[129] | 300 |
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| 301 | /**
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| 302 | * <p>
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| 303 | * Checks if the node is a leaf.
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| 304 | * </p>
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| 305 | *
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| 306 | * @return true if the node is a leaf, false otherwise.
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| 307 | */
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| 308 | protected boolean isLeaf() {
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| 309 | return children.isEmpty();
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| 310 | }
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[258] | 311 |
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[251] | 312 | /**
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| 313 | * <p>
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| 314 | * Checks if the node is the root.
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| 315 | * </p>
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| 316 | *
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| 317 | * @return true if the node is the root of the trie, false otherwise
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| 318 | */
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| 319 | protected boolean isRoot() {
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[258] | 320 | return symbol == null;
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[251] | 321 | }
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[129] | 322 |
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| 323 | /**
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| 324 | * <p>
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| 325 | * Recursive methods that collects all nodes that are ancestors of leafs and
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| 326 | * stores them in the set.
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| 327 | * </p>
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| 328 | *
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| 329 | * @param ancestors
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| 330 | * set of all ancestors of leafs
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| 331 | */
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| 332 | protected void getLeafAncestors(Set<TrieNode<T>> ancestors) {
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| 333 | boolean isAncestor = false;
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| 334 | for (TrieNode<T> child : children) {
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| 335 | child.getLeafAncestors(ancestors);
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| 336 | isAncestor |= child.isLeaf();
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| 337 | }
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| 338 | if (isAncestor) {
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| 339 | ancestors.add(this);
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| 340 | }
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| 341 | }
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[258] | 342 |
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[248] | 343 | /**
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[258] | 344 | * <p>
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| 345 | * Returns the number of descendants of this node that are leafs. This does
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| 346 | * not only include direct children of this node, but all leafs in the
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| 347 | * sub-trie with this node as root.
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[248] | 348 | * </p>
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[258] | 349 | *
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| 350 | * @return number of leafs in this sub-trie
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[248] | 351 | */
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| 352 | protected int getNumLeafs() {
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| 353 | int numLeafs = 0;
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[258] | 354 | for (TrieNode<T> child : children) {
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| 355 | if (child.isLeaf()) {
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[248] | 356 | numLeafs++;
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| 357 | } else {
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| 358 | numLeafs += child.getNumLeafs();
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| 359 | }
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| 360 | }
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| 361 | return numLeafs;
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| 362 | }
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[258] | 363 |
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| 364 | /**
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| 365 | * <p>
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| 366 | * Sets the {@link #count} of this node.
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| 367 | * </p>
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| 368 | * <p>
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| 369 | * This function should only be used sparingly and very carefully! The count
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| 370 | * is usually maintained automatically by the training procedures.
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| 371 | * </p>
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| 372 | *
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| 373 | * @param count
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| 374 | * new count
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| 375 | */
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| 376 | protected void setCount(int count) {
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| 377 | this.count = count;
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| 378 | }
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[1] | 379 | }
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