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| 1 | /* | ||
| 2 | * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.util; | ||
| 27 | import java.io.*; | ||
| 28 | |||
| 29 | /** | ||
| 30 | * This class implements a hash table, which maps keys to values. Any | ||
| 31 | * non-<code>null</code> object can be used as a key or as a value. <p> | ||
| 32 | * | ||
| 33 | * To successfully store and retrieve objects from a hashtable, the | ||
| 34 | * objects used as keys must implement the <code>hashCode</code> | ||
| 35 | * method and the <code>equals</code> method. <p> | ||
| 36 | * | ||
| 37 | * An instance of <code>Hashtable</code> has two parameters that affect its | ||
| 38 | * performance: <i>initial capacity</i> and <i>load factor</i>. The | ||
| 39 | * <i>capacity</i> is the number of <i>buckets</i> in the hash table, and the | ||
| 40 | * <i>initial capacity</i> is simply the capacity at the time the hash table | ||
| 41 | * is created. Note that the hash table is <i>open</i>: in the case of a "hash | ||
| 42 | * collision", a single bucket stores multiple entries, which must be searched | ||
| 43 | * sequentially. The <i>load factor</i> is a measure of how full the hash | ||
| 44 | * table is allowed to get before its capacity is automatically increased. | ||
| 45 | * The initial capacity and load factor parameters are merely hints to | ||
| 46 | * the implementation. The exact details as to when and whether the rehash | ||
| 47 | * method is invoked are implementation-dependent.<p> | ||
| 48 | * | ||
| 49 | * Generally, the default load factor (.75) offers a good tradeoff between | ||
| 50 | * time and space costs. Higher values decrease the space overhead but | ||
| 51 | * increase the time cost to look up an entry (which is reflected in most | ||
| 52 | * <tt>Hashtable</tt> operations, including <tt>get</tt> and <tt>put</tt>).<p> | ||
| 53 | * | ||
| 54 | * The initial capacity controls a tradeoff between wasted space and the | ||
| 55 | * need for <code>rehash</code> operations, which are time-consuming. | ||
| 56 | * No <code>rehash</code> operations will <i>ever</i> occur if the initial | ||
| 57 | * capacity is greater than the maximum number of entries the | ||
| 58 | * <tt>Hashtable</tt> will contain divided by its load factor. However, | ||
| 59 | * setting the initial capacity too high can waste space.<p> | ||
| 60 | * | ||
| 61 | * If many entries are to be made into a <code>Hashtable</code>, | ||
| 62 | * creating it with a sufficiently large capacity may allow the | ||
| 63 | * entries to be inserted more efficiently than letting it perform | ||
| 64 | * automatic rehashing as needed to grow the table. <p> | ||
| 65 | * | ||
| 66 | * This example creates a hashtable of numbers. It uses the names of | ||
| 67 | * the numbers as keys: | ||
| 68 | * <pre> {@code | ||
| 69 | * Hashtable<String, Integer> numbers | ||
| 70 | * = new Hashtable<String, Integer>(); | ||
| 71 | * numbers.put("one", 1); | ||
| 72 | * numbers.put("two", 2); | ||
| 73 | * numbers.put("three", 3);}</pre> | ||
| 74 | * | ||
| 75 | * <p>To retrieve a number, use the following code: | ||
| 76 | * <pre> {@code | ||
| 77 | * Integer n = numbers.get("two"); | ||
| 78 | * if (n != null) { | ||
| 79 | * System.out.println("two = " + n); | ||
| 80 | * }}</pre> | ||
| 81 | * | ||
| 82 | * <p>The iterators returned by the <tt>iterator</tt> method of the collections | ||
| 83 | * returned by all of this class's "collection view methods" are | ||
| 84 | * <em>fail-fast</em>: if the Hashtable is structurally modified at any time | ||
| 85 | * after the iterator is created, in any way except through the iterator's own | ||
| 86 | * <tt>remove</tt> method, the iterator will throw a {@link | ||
| 87 | * ConcurrentModificationException}. Thus, in the face of concurrent | ||
| 88 | * modification, the iterator fails quickly and cleanly, rather than risking | ||
| 89 | * arbitrary, non-deterministic behavior at an undetermined time in the future. | ||
| 90 | * The Enumerations returned by Hashtable's keys and elements methods are | ||
| 91 | * <em>not</em> fail-fast. | ||
| 92 | * | ||
| 93 | * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed | ||
| 94 | * as it is, generally speaking, impossible to make any hard guarantees in the | ||
| 95 | * presence of unsynchronized concurrent modification. Fail-fast iterators | ||
| 96 | * throw <tt>ConcurrentModificationException</tt> on a best-effort basis. | ||
| 97 | * Therefore, it would be wrong to write a program that depended on this | ||
| 98 | * exception for its correctness: <i>the fail-fast behavior of iterators | ||
| 99 | * should be used only to detect bugs.</i> | ||
| 100 | * | ||
| 101 | * <p>As of the Java 2 platform v1.2, this class was retrofitted to | ||
| 102 | * implement the {@link Map} interface, making it a member of the | ||
| 103 | * <a href="{@docRoot}/../technotes/guides/collections/index.html"> | ||
| 104 | * | ||
| 105 | * Java Collections Framework</a>. Unlike the new collection | ||
| 106 | * implementations, {@code Hashtable} is synchronized. If a | ||
| 107 | * thread-safe implementation is not needed, it is recommended to use | ||
| 108 | * {@link HashMap} in place of {@code Hashtable}. If a thread-safe | ||
| 109 | * highly-concurrent implementation is desired, then it is recommended | ||
| 110 | * to use {@link java.util.concurrent.ConcurrentHashMap} in place of | ||
| 111 | * {@code Hashtable}. | ||
| 112 | * | ||
| 113 | * @author Arthur van Hoff | ||
| 114 | * @author Josh Bloch | ||
| 115 | * @author Neal Gafter | ||
| 116 | * @see Object#equals(java.lang.Object) | ||
| 117 | * @see Object#hashCode() | ||
| 118 | * @see Hashtable#rehash() | ||
| 119 | * @see Collection | ||
| 120 | * @see Map | ||
| 121 | * @see HashMap | ||
| 122 | * @see TreeMap | ||
| 123 | * @since JDK1.0 | ||
| 124 | */ | ||
| 125 | public class Hashtable<K,V> | ||
| 126 | extends Dictionary<K,V> | ||
| 127 | implements Map<K,V>, Cloneable, java.io.Serializable { | ||
| 128 | |||
| 129 | /** | ||
| 130 | * The hash table data. | ||
| 131 | */ | ||
| 132 | private transient Entry[] table; | ||
| 133 | |||
| 134 | /** | ||
| 135 | * The total number of entries in the hash table. | ||
| 136 | */ | ||
| 137 | private transient int count; | ||
| 138 | |||
| 139 | /** | ||
| 140 | * The table is rehashed when its size exceeds this threshold. (The | ||
| 141 | * value of this field is (int)(capacity * loadFactor).) | ||
| 142 | * | ||
| 143 | * @serial | ||
| 144 | */ | ||
| 145 | private int threshold; | ||
| 146 | |||
| 147 | /** | ||
| 148 | * The load factor for the hashtable. | ||
| 149 | * | ||
| 150 | * @serial | ||
| 151 | */ | ||
| 152 | private float loadFactor; | ||
| 153 | |||
| 154 | /** | ||
| 155 | * The number of times this Hashtable has been structurally modified | ||
| 156 | * Structural modifications are those that change the number of entries in | ||
| 157 | * the Hashtable or otherwise modify its internal structure (e.g., | ||
| 158 | * rehash). This field is used to make iterators on Collection-views of | ||
| 159 | * the Hashtable fail-fast. (See ConcurrentModificationException). | ||
| 160 | */ | ||
| 161 | private transient int modCount = 0; | ||
| 162 | |||
| 163 | /** use serialVersionUID from JDK 1.0.2 for interoperability */ | ||
| 164 | private static final long serialVersionUID = 1421746759512286392L; | ||
| 165 | |||
| 166 | /** | ||
| 167 | * Constructs a new, empty hashtable with the specified initial | ||
| 168 | * capacity and the specified load factor. | ||
| 169 | * | ||
| 170 | * @param initialCapacity the initial capacity of the hashtable. | ||
| 171 | * @param loadFactor the load factor of the hashtable. | ||
| 172 | * @exception IllegalArgumentException if the initial capacity is less | ||
| 173 | * than zero, or if the load factor is nonpositive. | ||
| 174 | */ | ||
| 175 | public Hashtable(int initialCapacity, float loadFactor) { | ||
| 176 | if (initialCapacity < 0) | ||
| 177 | throw new IllegalArgumentException("Illegal Capacity: "+ | ||
| 178 | initialCapacity); | ||
| 179 | if (loadFactor <= 0 || Float.isNaN(loadFactor)) | ||
| 180 | throw new IllegalArgumentException("Illegal Load: "+loadFactor); | ||
| 181 | |||
| 182 | if (initialCapacity==0) | ||
| 183 | initialCapacity = 1; | ||
| 184 | this.loadFactor = loadFactor; | ||
| 185 | table = new Entry[initialCapacity]; | ||
| 186 | threshold = (int)(initialCapacity * loadFactor); | ||
| 187 | } | ||
| 188 | |||
| 189 | /** | ||
| 190 | * Constructs a new, empty hashtable with the specified initial capacity | ||
| 191 | * and default load factor (0.75). | ||
| 192 | * | ||
| 193 | * @param initialCapacity the initial capacity of the hashtable. | ||
| 194 | * @exception IllegalArgumentException if the initial capacity is less | ||
| 195 | * than zero. | ||
| 196 | */ | ||
| 197 | public Hashtable(int initialCapacity) { | ||
| 198 | this(initialCapacity, 0.75f); | ||
| 199 | } | ||
| 200 | |||
| 201 | /** | ||
| 202 | * Constructs a new, empty hashtable with a default initial capacity (11) | ||
| 203 | * and load factor (0.75). | ||
| 204 | */ | ||
| 205 | public Hashtable() { | ||
| 206 | this(11, 0.75f); | ||
| 207 | } | ||
| 208 | |||
| 209 | /** | ||
| 210 | * Constructs a new hashtable with the same mappings as the given | ||
| 211 | * Map. The hashtable is created with an initial capacity sufficient to | ||
| 212 | * hold the mappings in the given Map and a default load factor (0.75). | ||
| 213 | * | ||
| 214 | * @param t the map whose mappings are to be placed in this map. | ||
| 215 | * @throws NullPointerException if the specified map is null. | ||
| 216 | * @since 1.2 | ||
| 217 | */ | ||
| 218 | public Hashtable(Map<? extends K, ? extends V> t) { | ||
| 219 | this(Math.max(2*t.size(), 11), 0.75f); | ||
| 220 | putAll(t); | ||
| 221 | } | ||
| 222 | |||
| 223 | /** | ||
| 224 | * Returns the number of keys in this hashtable. | ||
| 225 | * | ||
| 226 | * @return the number of keys in this hashtable. | ||
| 227 | */ | ||
| 228 | public synchronized int size() { | ||
| 229 | return count; | ||
| 230 | } | ||
| 231 | |||
| 232 | /** | ||
| 233 | * Tests if this hashtable maps no keys to values. | ||
| 234 | * | ||
| 235 | * @return <code>true</code> if this hashtable maps no keys to values; | ||
| 236 | * <code>false</code> otherwise. | ||
| 237 | */ | ||
| 238 | public synchronized boolean isEmpty() { | ||
| 239 | return count == 0; | ||
| 240 | } | ||
| 241 | |||
| 242 | /** | ||
| 243 | * Returns an enumeration of the keys in this hashtable. | ||
| 244 | * | ||
| 245 | * @return an enumeration of the keys in this hashtable. | ||
| 246 | * @see Enumeration | ||
| 247 | * @see #elements() | ||
| 248 | * @see #keySet() | ||
| 249 | * @see Map | ||
| 250 | */ | ||
| 251 | public synchronized Enumeration<K> keys() { | ||
| 252 | return this.<K>getEnumeration(KEYS); | ||
| 253 | } | ||
| 254 | |||
| 255 | /** | ||
| 256 | * Returns an enumeration of the values in this hashtable. | ||
| 257 | * Use the Enumeration methods on the returned object to fetch the elements | ||
| 258 | * sequentially. | ||
| 259 | * | ||
| 260 | * @return an enumeration of the values in this hashtable. | ||
| 261 | * @see java.util.Enumeration | ||
| 262 | * @see #keys() | ||
| 263 | * @see #values() | ||
| 264 | * @see Map | ||
| 265 | */ | ||
| 266 | public synchronized Enumeration<V> elements() { | ||
| 267 | return this.<V>getEnumeration(VALUES); | ||
| 268 | } | ||
| 269 | |||
| 270 | /** | ||
| 271 | * Tests if some key maps into the specified value in this hashtable. | ||
| 272 | * This operation is more expensive than the {@link #containsKey | ||
| 273 | * containsKey} method. | ||
| 274 | * | ||
| 275 | * <p>Note that this method is identical in functionality to | ||
| 276 | * {@link #containsValue containsValue}, (which is part of the | ||
| 277 | * {@link Map} interface in the collections framework). | ||
| 278 | * | ||
| 279 | * @param value a value to search for | ||
| 280 | * @return <code>true</code> if and only if some key maps to the | ||
| 281 | * <code>value</code> argument in this hashtable as | ||
| 282 | * determined by the <tt>equals</tt> method; | ||
| 283 | * <code>false</code> otherwise. | ||
| 284 | * @exception NullPointerException if the value is <code>null</code> | ||
| 285 | */ | ||
| 286 | public synchronized boolean contains(Object value) { | ||
| 287 | if (value == null) { | ||
| 288 | throw new NullPointerException(); | ||
| 289 | } | ||
| 290 | |||
| 291 | Entry tab[] = table; | ||
| 292 | for (int i = tab.length ; i-- > 0 ;) { | ||
| 293 | for (Entry<K,V> e = tab[i] ; e != null ; e = e.next) { | ||
| 294 | if (e.value.equals(value)) { | ||
| 295 | return true; | ||
| 296 | } | ||
| 297 | } | ||
| 298 | } | ||
| 299 | return false; | ||
| 300 | } | ||
| 301 | |||
| 302 | /** | ||
| 303 | * Returns true if this hashtable maps one or more keys to this value. | ||
| 304 | * | ||
| 305 | * <p>Note that this method is identical in functionality to {@link | ||
| 306 | * #contains contains} (which predates the {@link Map} interface). | ||
| 307 | * | ||
| 308 | * @param value value whose presence in this hashtable is to be tested | ||
| 309 | * @return <tt>true</tt> if this map maps one or more keys to the | ||
| 310 | * specified value | ||
| 311 | * @throws NullPointerException if the value is <code>null</code> | ||
| 312 | * @since 1.2 | ||
| 313 | */ | ||
| 314 | public boolean containsValue(Object value) { | ||
| 315 | return contains(value); | ||
| 316 | } | ||
| 317 | |||
| 318 | /** | ||
| 319 | * Tests if the specified object is a key in this hashtable. | ||
| 320 | * | ||
| 321 | * @param key possible key | ||
| 322 | * @return <code>true</code> if and only if the specified object | ||
| 323 | * is a key in this hashtable, as determined by the | ||
| 324 | * <tt>equals</tt> method; <code>false</code> otherwise. | ||
| 325 | * @throws NullPointerException if the key is <code>null</code> | ||
| 326 | * @see #contains(Object) | ||
| 327 | */ | ||
| 328 | public synchronized boolean containsKey(Object key) { | ||
| 329 | Entry tab[] = table; | ||
| 330 | int hash = key.hashCode(); | ||
| 331 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 332 | for (Entry<K,V> e = tab[index] ; e != null ; e = e.next) { | ||
| 333 | if ((e.hash == hash) && e.key.equals(key)) { | ||
| 334 | return true; | ||
| 335 | } | ||
| 336 | } | ||
| 337 | return false; | ||
| 338 | } | ||
| 339 | |||
| 340 | /** | ||
| 341 | * Returns the value to which the specified key is mapped, | ||
| 342 | * or {@code null} if this map contains no mapping for the key. | ||
| 343 | * | ||
| 344 | * <p>More formally, if this map contains a mapping from a key | ||
| 345 | * {@code k} to a value {@code v} such that {@code (key.equals(k))}, | ||
| 346 | * then this method returns {@code v}; otherwise it returns | ||
| 347 | * {@code null}. (There can be at most one such mapping.) | ||
| 348 | * | ||
| 349 | * @param key the key whose associated value is to be returned | ||
| 350 | * @return the value to which the specified key is mapped, or | ||
| 351 | * {@code null} if this map contains no mapping for the key | ||
| 352 | * @throws NullPointerException if the specified key is null | ||
| 353 | * @see #put(Object, Object) | ||
| 354 | */ | ||
| 355 | public synchronized V get(Object key) { | ||
| 356 | Entry tab[] = table; | ||
| 357 | int hash = key.hashCode(); | ||
| 358 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 359 | for (Entry<K,V> e = tab[index] ; e != null ; e = e.next) { | ||
| 360 | if ((e.hash == hash) && e.key.equals(key)) { | ||
| 361 | return e.value; | ||
| 362 | } | ||
| 363 | } | ||
| 364 | return null; | ||
| 365 | } | ||
| 366 | |||
| 367 | /** | ||
| 368 | * The maximum size of array to allocate. | ||
| 369 | * Some VMs reserve some header words in an array. | ||
| 370 | * Attempts to allocate larger arrays may result in | ||
| 371 | * OutOfMemoryError: Requested array size exceeds VM limit | ||
| 372 | */ | ||
| 373 | private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; | ||
| 374 | |||
| 375 | /** | ||
| 376 | * Increases the capacity of and internally reorganizes this | ||
| 377 | * hashtable, in order to accommodate and access its entries more | ||
| 378 | * efficiently. This method is called automatically when the | ||
| 379 | * number of keys in the hashtable exceeds this hashtable's capacity | ||
| 380 | * and load factor. | ||
| 381 | */ | ||
| 382 | protected void rehash() { | ||
| 383 | int oldCapacity = table.length; | ||
| 384 | Entry[] oldMap = table; | ||
| 385 | |||
| 386 | // overflow-conscious code | ||
| 387 | int newCapacity = (oldCapacity << 1) + 1; | ||
| 388 | if (newCapacity - MAX_ARRAY_SIZE > 0) { | ||
| 389 | if (oldCapacity == MAX_ARRAY_SIZE) | ||
| 390 | // Keep running with MAX_ARRAY_SIZE buckets | ||
| 391 | return; | ||
| 392 | newCapacity = MAX_ARRAY_SIZE; | ||
| 393 | } | ||
| 394 | Entry[] newMap = new Entry[newCapacity]; | ||
| 395 | |||
| 396 | modCount++; | ||
| 397 | threshold = (int)(newCapacity * loadFactor); | ||
| 398 | table = newMap; | ||
| 399 | |||
| 400 | for (int i = oldCapacity ; i-- > 0 ;) { | ||
| 401 | for (Entry<K,V> old = oldMap[i] ; old != null ; ) { | ||
| 402 | Entry<K,V> e = old; | ||
| 403 | old = old.next; | ||
| 404 | |||
| 405 | int index = (e.hash & 0x7FFFFFFF) % newCapacity; | ||
| 406 | e.next = newMap[index]; | ||
| 407 | newMap[index] = e; | ||
| 408 | } | ||
| 409 | } | ||
| 410 | } | ||
| 411 | |||
| 412 | /** | ||
| 413 | * Maps the specified <code>key</code> to the specified | ||
| 414 | * <code>value</code> in this hashtable. Neither the key nor the | ||
| 415 | * value can be <code>null</code>. <p> | ||
| 416 | * | ||
| 417 | * The value can be retrieved by calling the <code>get</code> method | ||
| 418 | * with a key that is equal to the original key. | ||
| 419 | * | ||
| 420 | * @param key the hashtable key | ||
| 421 | * @param value the value | ||
| 422 | * @return the previous value of the specified key in this hashtable, | ||
| 423 | * or <code>null</code> if it did not have one | ||
| 424 | * @exception NullPointerException if the key or value is | ||
| 425 | * <code>null</code> | ||
| 426 | * @see Object#equals(Object) | ||
| 427 | * @see #get(Object) | ||
| 428 | */ | ||
| 429 | public synchronized V put(K key, V value) { | ||
| 430 | // Make sure the value is not null | ||
| 431 | if (value == null) { | ||
| 432 | throw new NullPointerException(); | ||
| 433 | } | ||
| 434 | |||
| 435 | // Makes sure the key is not already in the hashtable. | ||
| 436 | Entry tab[] = table; | ||
| 437 | int hash = key.hashCode(); | ||
| 438 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 439 | for (Entry<K,V> e = tab[index] ; e != null ; e = e.next) { | ||
| 440 | if ((e.hash == hash) && e.key.equals(key)) { | ||
| 441 | V old = e.value; | ||
| 442 | e.value = value; | ||
| 443 | return old; | ||
| 444 | } | ||
| 445 | } | ||
| 446 | |||
| 447 | modCount++; | ||
| 448 | if (count >= threshold) { | ||
| 449 | // Rehash the table if the threshold is exceeded | ||
| 450 | rehash(); | ||
| 451 | |||
| 452 | tab = table; | ||
| 453 | index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 454 | } | ||
| 455 | |||
| 456 | // Creates the new entry. | ||
| 457 | Entry<K,V> e = tab[index]; | ||
| 458 | tab[index] = new Entry<>(hash, key, value, e); | ||
| 459 | count++; | ||
| 460 | return null; | ||
| 461 | } | ||
| 462 | |||
| 463 | /** | ||
| 464 | * Removes the key (and its corresponding value) from this | ||
| 465 | * hashtable. This method does nothing if the key is not in the hashtable. | ||
| 466 | * | ||
| 467 | * @param key the key that needs to be removed | ||
| 468 | * @return the value to which the key had been mapped in this hashtable, | ||
| 469 | * or <code>null</code> if the key did not have a mapping | ||
| 470 | * @throws NullPointerException if the key is <code>null</code> | ||
| 471 | */ | ||
| 472 | public synchronized V remove(Object key) { | ||
| 473 | Entry tab[] = table; | ||
| 474 | int hash = key.hashCode(); | ||
| 475 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 476 | for (Entry<K,V> e = tab[index], prev = null ; e != null ; prev = e, e = e.next) { | ||
| 477 | if ((e.hash == hash) && e.key.equals(key)) { | ||
| 478 | modCount++; | ||
| 479 | if (prev != null) { | ||
| 480 | prev.next = e.next; | ||
| 481 | } else { | ||
| 482 | tab[index] = e.next; | ||
| 483 | } | ||
| 484 | count--; | ||
| 485 | V oldValue = e.value; | ||
| 486 | e.value = null; | ||
| 487 | return oldValue; | ||
| 488 | } | ||
| 489 | } | ||
| 490 | return null; | ||
| 491 | } | ||
| 492 | |||
| 493 | /** | ||
| 494 | * Copies all of the mappings from the specified map to this hashtable. | ||
| 495 | * These mappings will replace any mappings that this hashtable had for any | ||
| 496 | * of the keys currently in the specified map. | ||
| 497 | * | ||
| 498 | * @param t mappings to be stored in this map | ||
| 499 | * @throws NullPointerException if the specified map is null | ||
| 500 | * @since 1.2 | ||
| 501 | */ | ||
| 502 | public synchronized void putAll(Map<? extends K, ? extends V> t) { | ||
| 503 | for (Map.Entry<? extends K, ? extends V> e : t.entrySet()) | ||
| 504 | put(e.getKey(), e.getValue()); | ||
| 505 | } | ||
| 506 | |||
| 507 | /** | ||
| 508 | * Clears this hashtable so that it contains no keys. | ||
| 509 | */ | ||
| 510 | public synchronized void clear() { | ||
| 511 | Entry tab[] = table; | ||
| 512 | modCount++; | ||
| 513 | for (int index = tab.length; --index >= 0; ) | ||
| 514 | tab[index] = null; | ||
| 515 | count = 0; | ||
| 516 | } | ||
| 517 | |||
| 518 | /** | ||
| 519 | * Creates a shallow copy of this hashtable. All the structure of the | ||
| 520 | * hashtable itself is copied, but the keys and values are not cloned. | ||
| 521 | * This is a relatively expensive operation. | ||
| 522 | * | ||
| 523 | * @return a clone of the hashtable | ||
| 524 | */ | ||
| 525 | public synchronized Object clone() { | ||
| 526 | try { | ||
| 527 | Hashtable<K,V> t = (Hashtable<K,V>) super.clone(); | ||
| 528 | t.table = new Entry[table.length]; | ||
| 529 | for (int i = table.length ; i-- > 0 ; ) { | ||
| 530 | t.table[i] = (table[i] != null) | ||
| 531 | ? (Entry<K,V>) table[i].clone() : null; | ||
| 532 | } | ||
| 533 | t.keySet = null; | ||
| 534 | t.entrySet = null; | ||
| 535 | t.values = null; | ||
| 536 | t.modCount = 0; | ||
| 537 | return t; | ||
| 538 | } catch (CloneNotSupportedException e) { | ||
| 539 | // this shouldn't happen, since we are Cloneable | ||
| 540 | throw new InternalError(); | ||
| 541 | } | ||
| 542 | } | ||
| 543 | |||
| 544 | /** | ||
| 545 | * Returns a string representation of this <tt>Hashtable</tt> object | ||
| 546 | * in the form of a set of entries, enclosed in braces and separated | ||
| 547 | * by the ASCII characters "<tt>, </tt>" (comma and space). Each | ||
| 548 | * entry is rendered as the key, an equals sign <tt>=</tt>, and the | ||
| 549 | * associated element, where the <tt>toString</tt> method is used to | ||
| 550 | * convert the key and element to strings. | ||
| 551 | * | ||
| 552 | * @return a string representation of this hashtable | ||
| 553 | */ | ||
| 554 | public synchronized String toString() { | ||
| 555 | int max = size() - 1; | ||
| 556 | if (max == -1) | ||
| 557 | return "{}"; | ||
| 558 | |||
| 559 | StringBuilder sb = new StringBuilder(); | ||
| 560 | Iterator<Map.Entry<K,V>> it = entrySet().iterator(); | ||
| 561 | |||
| 562 | sb.append('{'); | ||
| 563 | for (int i = 0; ; i++) { | ||
| 564 | Map.Entry<K,V> e = it.next(); | ||
| 565 | K key = e.getKey(); | ||
| 566 | V value = e.getValue(); | ||
| 567 | sb.append(key == this ? "(this Map)" : key.toString()); | ||
| 568 | sb.append('='); | ||
| 569 | sb.append(value == this ? "(this Map)" : value.toString()); | ||
| 570 | |||
| 571 | if (i == max) | ||
| 572 | return sb.append('}').toString(); | ||
| 573 | sb.append(", "); | ||
| 574 | } | ||
| 575 | } | ||
| 576 | |||
| 577 | |||
| 578 | private <T> Enumeration<T> getEnumeration(int type) { | ||
| 579 | if (count == 0) { | ||
| 580 | return Collections.emptyEnumeration(); | ||
| 581 | } else { | ||
| 582 | return new Enumerator<>(type, false); | ||
| 583 | } | ||
| 584 | } | ||
| 585 | |||
| 586 | private <T> Iterator<T> getIterator(int type) { | ||
| 587 | if (count == 0) { | ||
| 588 | return Collections.emptyIterator(); | ||
| 589 | } else { | ||
| 590 | return new Enumerator<>(type, true); | ||
| 591 | } | ||
| 592 | } | ||
| 593 | |||
| 594 | // Views | ||
| 595 | |||
| 596 | /** | ||
| 597 | * Each of these fields are initialized to contain an instance of the | ||
| 598 | * appropriate view the first time this view is requested. The views are | ||
| 599 | * stateless, so there's no reason to create more than one of each. | ||
| 600 | */ | ||
| 601 | private transient volatile Set<K> keySet = null; | ||
| 602 | private transient volatile Set<Map.Entry<K,V>> entrySet = null; | ||
| 603 | private transient volatile Collection<V> values = null; | ||
| 604 | |||
| 605 | /** | ||
| 606 | * Returns a {@link Set} view of the keys contained in this map. | ||
| 607 | * The set is backed by the map, so changes to the map are | ||
| 608 | * reflected in the set, and vice-versa. If the map is modified | ||
| 609 | * while an iteration over the set is in progress (except through | ||
| 610 | * the iterator's own <tt>remove</tt> operation), the results of | ||
| 611 | * the iteration are undefined. The set supports element removal, | ||
| 612 | * which removes the corresponding mapping from the map, via the | ||
| 613 | * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, | ||
| 614 | * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> | ||
| 615 | * operations. It does not support the <tt>add</tt> or <tt>addAll</tt> | ||
| 616 | * operations. | ||
| 617 | * | ||
| 618 | * @since 1.2 | ||
| 619 | */ | ||
| 620 | public Set<K> keySet() { | ||
| 621 | if (keySet == null) | ||
| 622 | keySet = Collections.synchronizedSet(new KeySet(), this); | ||
| 623 | return keySet; | ||
| 624 | } | ||
| 625 | |||
| 626 | private class KeySet extends AbstractSet<K> { | ||
| 627 | public Iterator<K> iterator() { | ||
| 628 | return getIterator(KEYS); | ||
| 629 | } | ||
| 630 | public int size() { | ||
| 631 | return count; | ||
| 632 | } | ||
| 633 | public boolean contains(Object o) { | ||
| 634 | return containsKey(o); | ||
| 635 | } | ||
| 636 | public boolean remove(Object o) { | ||
| 637 | return Hashtable.this.remove(o) != null; | ||
| 638 | } | ||
| 639 | public void clear() { | ||
| 640 | Hashtable.this.clear(); | ||
| 641 | } | ||
| 642 | } | ||
| 643 | |||
| 644 | /** | ||
| 645 | * Returns a {@link Set} view of the mappings contained in this map. | ||
| 646 | * The set is backed by the map, so changes to the map are | ||
| 647 | * reflected in the set, and vice-versa. If the map is modified | ||
| 648 | * while an iteration over the set is in progress (except through | ||
| 649 | * the iterator's own <tt>remove</tt> operation, or through the | ||
| 650 | * <tt>setValue</tt> operation on a map entry returned by the | ||
| 651 | * iterator) the results of the iteration are undefined. The set | ||
| 652 | * supports element removal, which removes the corresponding | ||
| 653 | * mapping from the map, via the <tt>Iterator.remove</tt>, | ||
| 654 | * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and | ||
| 655 | * <tt>clear</tt> operations. It does not support the | ||
| 656 | * <tt>add</tt> or <tt>addAll</tt> operations. | ||
| 657 | * | ||
| 658 | * @since 1.2 | ||
| 659 | */ | ||
| 660 | public Set<Map.Entry<K,V>> entrySet() { | ||
| 661 | if (entrySet==null) | ||
| 662 | entrySet = Collections.synchronizedSet(new EntrySet(), this); | ||
| 663 | return entrySet; | ||
| 664 | } | ||
| 665 | |||
| 666 | private class EntrySet extends AbstractSet<Map.Entry<K,V>> { | ||
| 667 | public Iterator<Map.Entry<K,V>> iterator() { | ||
| 668 | return getIterator(ENTRIES); | ||
| 669 | } | ||
| 670 | |||
| 671 | public boolean add(Map.Entry<K,V> o) { | ||
| 672 | return super.add(o); | ||
| 673 | } | ||
| 674 | |||
| 675 | public boolean contains(Object o) { | ||
| 676 | if (!(o instanceof Map.Entry)) | ||
| 677 | return false; | ||
| 678 | Map.Entry entry = (Map.Entry)o; | ||
| 679 | Object key = entry.getKey(); | ||
| 680 | Entry[] tab = table; | ||
| 681 | int hash = key.hashCode(); | ||
| 682 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 683 | |||
| 684 | for (Entry e = tab[index]; e != null; e = e.next) | ||
| 685 | if (e.hash==hash && e.equals(entry)) | ||
| 686 | return true; | ||
| 687 | return false; | ||
| 688 | } | ||
| 689 | |||
| 690 | public boolean remove(Object o) { | ||
| 691 | if (!(o instanceof Map.Entry)) | ||
| 692 | return false; | ||
| 693 | Map.Entry<K,V> entry = (Map.Entry<K,V>) o; | ||
| 694 | K key = entry.getKey(); | ||
| 695 | Entry[] tab = table; | ||
| 696 | int hash = key.hashCode(); | ||
| 697 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 698 | |||
| 699 | for (Entry<K,V> e = tab[index], prev = null; e != null; | ||
| 700 | prev = e, e = e.next) { | ||
| 701 | if (e.hash==hash && e.equals(entry)) { | ||
| 702 | modCount++; | ||
| 703 | if (prev != null) | ||
| 704 | prev.next = e.next; | ||
| 705 | else | ||
| 706 | tab[index] = e.next; | ||
| 707 | |||
| 708 | count--; | ||
| 709 | e.value = null; | ||
| 710 | return true; | ||
| 711 | } | ||
| 712 | } | ||
| 713 | return false; | ||
| 714 | } | ||
| 715 | |||
| 716 | public int size() { | ||
| 717 | return count; | ||
| 718 | } | ||
| 719 | |||
| 720 | public void clear() { | ||
| 721 | Hashtable.this.clear(); | ||
| 722 | } | ||
| 723 | } | ||
| 724 | |||
| 725 | /** | ||
| 726 | * Returns a {@link Collection} view of the values contained in this map. | ||
| 727 | * The collection is backed by the map, so changes to the map are | ||
| 728 | * reflected in the collection, and vice-versa. If the map is | ||
| 729 | * modified while an iteration over the collection is in progress | ||
| 730 | * (except through the iterator's own <tt>remove</tt> operation), | ||
| 731 | * the results of the iteration are undefined. The collection | ||
| 732 | * supports element removal, which removes the corresponding | ||
| 733 | * mapping from the map, via the <tt>Iterator.remove</tt>, | ||
| 734 | * <tt>Collection.remove</tt>, <tt>removeAll</tt>, | ||
| 735 | * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not | ||
| 736 | * support the <tt>add</tt> or <tt>addAll</tt> operations. | ||
| 737 | * | ||
| 738 | * @since 1.2 | ||
| 739 | */ | ||
| 740 | public Collection<V> values() { | ||
| 741 | if (values==null) | ||
| 742 | values = Collections.synchronizedCollection(new ValueCollection(), | ||
| 743 | this); | ||
| 744 | return values; | ||
| 745 | } | ||
| 746 | |||
| 747 | private class ValueCollection extends AbstractCollection<V> { | ||
| 748 | public Iterator<V> iterator() { | ||
| 749 | return getIterator(VALUES); | ||
| 750 | } | ||
| 751 | public int size() { | ||
| 752 | return count; | ||
| 753 | } | ||
| 754 | public boolean contains(Object o) { | ||
| 755 | return containsValue(o); | ||
| 756 | } | ||
| 757 | public void clear() { | ||
| 758 | Hashtable.this.clear(); | ||
| 759 | } | ||
| 760 | } | ||
| 761 | |||
| 762 | // Comparison and hashing | ||
| 763 | |||
| 764 | /** | ||
| 765 | * Compares the specified Object with this Map for equality, | ||
| 766 | * as per the definition in the Map interface. | ||
| 767 | * | ||
| 768 | * @param o object to be compared for equality with this hashtable | ||
| 769 | * @return true if the specified Object is equal to this Map | ||
| 770 | * @see Map#equals(Object) | ||
| 771 | * @since 1.2 | ||
| 772 | */ | ||
| 773 | public synchronized boolean equals(Object o) { | ||
| 774 | if (o == this) | ||
| 775 | return true; | ||
| 776 | |||
| 777 | if (!(o instanceof Map)) | ||
| 778 | return false; | ||
| 779 | Map<K,V> t = (Map<K,V>) o; | ||
| 780 | if (t.size() != size()) | ||
| 781 | return false; | ||
| 782 | |||
| 783 | try { | ||
| 784 | Iterator<Map.Entry<K,V>> i = entrySet().iterator(); | ||
| 785 | while (i.hasNext()) { | ||
| 786 | Map.Entry<K,V> e = i.next(); | ||
| 787 | K key = e.getKey(); | ||
| 788 | V value = e.getValue(); | ||
| 789 | if (value == null) { | ||
| 790 | if (!(t.get(key)==null && t.containsKey(key))) | ||
| 791 | return false; | ||
| 792 | } else { | ||
| 793 | if (!value.equals(t.get(key))) | ||
| 794 | return false; | ||
| 795 | } | ||
| 796 | } | ||
| 797 | } catch (ClassCastException unused) { | ||
| 798 | return false; | ||
| 799 | } catch (NullPointerException unused) { | ||
| 800 | return false; | ||
| 801 | } | ||
| 802 | |||
| 803 | return true; | ||
| 804 | } | ||
| 805 | |||
| 806 | /** | ||
| 807 | * Returns the hash code value for this Map as per the definition in the | ||
| 808 | * Map interface. | ||
| 809 | * | ||
| 810 | * @see Map#hashCode() | ||
| 811 | * @since 1.2 | ||
| 812 | */ | ||
| 813 | public synchronized int hashCode() { | ||
| 814 | /* | ||
| 815 | * This code detects the recursion caused by computing the hash code | ||
| 816 | * of a self-referential hash table and prevents the stack overflow | ||
| 817 | * that would otherwise result. This allows certain 1.1-era | ||
| 818 | * applets with self-referential hash tables to work. This code | ||
| 819 | * abuses the loadFactor field to do double-duty as a hashCode | ||
| 820 | * in progress flag, so as not to worsen the space performance. | ||
| 821 | * A negative load factor indicates that hash code computation is | ||
| 822 | * in progress. | ||
| 823 | */ | ||
| 824 | int h = 0; | ||
| 825 | if (count == 0 || loadFactor < 0) | ||
| 826 | return h; // Returns zero | ||
| 827 | |||
| 828 | loadFactor = -loadFactor; // Mark hashCode computation in progress | ||
| 829 | Entry[] tab = table; | ||
| 830 | for (int i = 0; i < tab.length; i++) | ||
| 831 | for (Entry e = tab[i]; e != null; e = e.next) | ||
| 832 | h += e.key.hashCode() ^ e.value.hashCode(); | ||
| 833 | loadFactor = -loadFactor; // Mark hashCode computation complete | ||
| 834 | |||
| 835 | return h; | ||
| 836 | } | ||
| 837 | |||
| 838 | /** | ||
| 839 | * Save the state of the Hashtable to a stream (i.e., serialize it). | ||
| 840 | * | ||
| 841 | * @serialData The <i>capacity</i> of the Hashtable (the length of the | ||
| 842 | * bucket array) is emitted (int), followed by the | ||
| 843 | * <i>size</i> of the Hashtable (the number of key-value | ||
| 844 | * mappings), followed by the key (Object) and value (Object) | ||
| 845 | * for each key-value mapping represented by the Hashtable | ||
| 846 | * The key-value mappings are emitted in no particular order. | ||
| 847 | */ | ||
| 848 | private void writeObject(java.io.ObjectOutputStream s) | ||
| 849 | throws IOException { | ||
| 850 | Entry<Object, Object> entryStack = null; | ||
| 851 | |||
| 852 | synchronized (this) { | ||
| 853 | // Write out the length, threshold, loadfactor | ||
| 854 | s.defaultWriteObject(); | ||
| 855 | |||
| 856 | // Write out length, count of elements | ||
| 857 | s.writeInt(table.length); | ||
| 858 | s.writeInt(count); | ||
| 859 | |||
| 860 | // Stack copies of the entries in the table | ||
| 861 | for (int index = 0; index < table.length; index++) { | ||
| 862 | Entry entry = table[index]; | ||
| 863 | |||
| 864 | while (entry != null) { | ||
| 865 | entryStack = | ||
| 866 | new Entry<>(0, entry.key, entry.value, entryStack); | ||
| 867 | entry = entry.next; | ||
| 868 | } | ||
| 869 | } | ||
| 870 | } | ||
| 871 | |||
| 872 | // Write out the key/value objects from the stacked entries | ||
| 873 | while (entryStack != null) { | ||
| 874 | s.writeObject(entryStack.key); | ||
| 875 | s.writeObject(entryStack.value); | ||
| 876 | entryStack = entryStack.next; | ||
| 877 | } | ||
| 878 | } | ||
| 879 | |||
| 880 | /** | ||
| 881 | * Reconstitute the Hashtable from a stream (i.e., deserialize it). | ||
| 882 | */ | ||
| 883 | private void readObject(java.io.ObjectInputStream s) | ||
| 884 | throws IOException, ClassNotFoundException | ||
| 885 | { | ||
| 886 | // Read in the length, threshold, and loadfactor | ||
| 887 | s.defaultReadObject(); | ||
| 888 | |||
| 889 | // Read the original length of the array and number of elements | ||
| 890 | int origlength = s.readInt(); | ||
| 891 | int elements = s.readInt(); | ||
| 892 | |||
| 893 | // Compute new size with a bit of room 5% to grow but | ||
| 894 | // no larger than the original size. Make the length | ||
| 895 | // odd if it's large enough, this helps distribute the entries. | ||
| 896 | // Guard against the length ending up zero, that's not valid. | ||
| 897 | int length = (int)(elements * loadFactor) + (elements / 20) + 3; | ||
| 898 | if (length > elements && (length & 1) == 0) | ||
| 899 | length--; | ||
| 900 | if (origlength > 0 && length > origlength) | ||
| 901 | length = origlength; | ||
| 902 | |||
| 903 | Entry[] table = new Entry[length]; | ||
| 904 | count = 0; | ||
| 905 | |||
| 906 | // Read the number of elements and then all the key/value objects | ||
| 907 | for (; elements > 0; elements--) { | ||
| 908 | K key = (K)s.readObject(); | ||
| 909 | V value = (V)s.readObject(); | ||
| 910 | // synch could be eliminated for performance | ||
| 911 | reconstitutionPut(table, key, value); | ||
| 912 | } | ||
| 913 | this.table = table; | ||
| 914 | } | ||
| 915 | |||
| 916 | /** | ||
| 917 | * The put method used by readObject. This is provided because put | ||
| 918 | * is overridable and should not be called in readObject since the | ||
| 919 | * subclass will not yet be initialized. | ||
| 920 | * | ||
| 921 | * <p>This differs from the regular put method in several ways. No | ||
| 922 | * checking for rehashing is necessary since the number of elements | ||
| 923 | * initially in the table is known. The modCount is not incremented | ||
| 924 | * because we are creating a new instance. Also, no return value | ||
| 925 | * is needed. | ||
| 926 | */ | ||
| 927 | private void reconstitutionPut(Entry[] tab, K key, V value) | ||
| 928 | throws StreamCorruptedException | ||
| 929 | { | ||
| 930 | if (value == null) { | ||
| 931 | throw new java.io.StreamCorruptedException(); | ||
| 932 | } | ||
| 933 | // Makes sure the key is not already in the hashtable. | ||
| 934 | // This should not happen in deserialized version. | ||
| 935 | int hash = key.hashCode(); | ||
| 936 | int index = (hash & 0x7FFFFFFF) % tab.length; | ||
| 937 | for (Entry<K,V> e = tab[index] ; e != null ; e = e.next) { | ||
| 938 | if ((e.hash == hash) && e.key.equals(key)) { | ||
| 939 | throw new java.io.StreamCorruptedException(); | ||
| 940 | } | ||
| 941 | } | ||
| 942 | // Creates the new entry. | ||
| 943 | Entry<K,V> e = tab[index]; | ||
| 944 | tab[index] = new Entry<>(hash, key, value, e); | ||
| 945 | count++; | ||
| 946 | } | ||
| 947 | |||
| 948 | /** | ||
| 949 | * Hashtable collision list. | ||
| 950 | */ | ||
| 951 | private static class Entry<K,V> implements Map.Entry<K,V> { | ||
| 952 | int hash; | ||
| 953 | K key; | ||
| 954 | V value; | ||
| 955 | Entry<K,V> next; | ||
| 956 | |||
| 957 | protected Entry(int hash, K key, V value, Entry<K,V> next) { | ||
| 958 | this.hash = hash; | ||
| 959 | this.key = key; | ||
| 960 | this.value = value; | ||
| 961 | this.next = next; | ||
| 962 | } | ||
| 963 | |||
| 964 | protected Object clone() { | ||
| 965 | return new Entry<>(hash, key, value, | ||
| 966 | (next==null ? null : (Entry<K,V>) next.clone())); | ||
| 967 | } | ||
| 968 | |||
| 969 | // Map.Entry Ops | ||
| 970 | |||
| 971 | public K getKey() { | ||
| 972 | return key; | ||
| 973 | } | ||
| 974 | |||
| 975 | public V getValue() { | ||
| 976 | return value; | ||
| 977 | } | ||
| 978 | |||
| 979 | public V setValue(V value) { | ||
| 980 | if (value == null) | ||
| 981 | throw new NullPointerException(); | ||
| 982 | |||
| 983 | V oldValue = this.value; | ||
| 984 | this.value = value; | ||
| 985 | return oldValue; | ||
| 986 | } | ||
| 987 | |||
| 988 | public boolean equals(Object o) { | ||
| 989 | if (!(o instanceof Map.Entry)) | ||
| 990 | return false; | ||
| 991 | Map.Entry e = (Map.Entry)o; | ||
| 992 | |||
| 993 | return (key==null ? e.getKey()==null : key.equals(e.getKey())) && | ||
| 994 | (value==null ? e.getValue()==null : value.equals(e.getValue())); | ||
| 995 | } | ||
| 996 | |||
| 997 | public int hashCode() { | ||
| 998 | return hash ^ (value==null ? 0 : value.hashCode()); | ||
| 999 | } | ||
| 1000 | |||
| 1001 | public String toString() { | ||
| 1002 | return key.toString()+"="+value.toString(); | ||
| 1003 | } | ||
| 1004 | } | ||
| 1005 | |||
| 1006 | // Types of Enumerations/Iterations | ||
| 1007 | private static final int KEYS = 0; | ||
| 1008 | private static final int VALUES = 1; | ||
| 1009 | private static final int ENTRIES = 2; | ||
| 1010 | |||
| 1011 | /** | ||
| 1012 | * A hashtable enumerator class. This class implements both the | ||
| 1013 | * Enumeration and Iterator interfaces, but individual instances | ||
| 1014 | * can be created with the Iterator methods disabled. This is necessary | ||
| 1015 | * to avoid unintentionally increasing the capabilities granted a user | ||
| 1016 | * by passing an Enumeration. | ||
| 1017 | */ | ||
| 1018 | private class Enumerator<T> implements Enumeration<T>, Iterator<T> { | ||
| 1019 | Entry[] table = Hashtable.this.table; | ||
| 1020 | int index = table.length; | ||
| 1021 | Entry<K,V> entry = null; | ||
| 1022 | Entry<K,V> lastReturned = null; | ||
| 1023 | int type; | ||
| 1024 | |||
| 1025 | /** | ||
| 1026 | * Indicates whether this Enumerator is serving as an Iterator | ||
| 1027 | * or an Enumeration. (true -> Iterator). | ||
| 1028 | */ | ||
| 1029 | boolean iterator; | ||
| 1030 | |||
| 1031 | /** | ||
| 1032 | * The modCount value that the iterator believes that the backing | ||
| 1033 | * Hashtable should have. If this expectation is violated, the iterator | ||
| 1034 | * has detected concurrent modification. | ||
| 1035 | */ | ||
| 1036 | protected int expectedModCount = modCount; | ||
| 1037 | |||
| 1038 | Enumerator(int type, boolean iterator) { | ||
| 1039 | this.type = type; | ||
| 1040 | this.iterator = iterator; | ||
| 1041 | } | ||
| 1042 | |||
| 1043 | public boolean hasMoreElements() { | ||
| 1044 | Entry<K,V> e = entry; | ||
| 1045 | int i = index; | ||
| 1046 | Entry[] t = table; | ||
| 1047 | /* Use locals for faster loop iteration */ | ||
| 1048 | while (e == null && i > 0) { | ||
| 1049 | e = t[--i]; | ||
| 1050 | } | ||
| 1051 | entry = e; | ||
| 1052 | index = i; | ||
| 1053 | return e != null; | ||
| 1054 | } | ||
| 1055 | |||
| 1056 | public T nextElement() { | ||
| 1057 | Entry<K,V> et = entry; | ||
| 1058 | int i = index; | ||
| 1059 | Entry[] t = table; | ||
| 1060 | /* Use locals for faster loop iteration */ | ||
| 1061 | while (et == null && i > 0) { | ||
| 1062 | et = t[--i]; | ||
| 1063 | } | ||
| 1064 | entry = et; | ||
| 1065 | index = i; | ||
| 1066 | if (et != null) { | ||
| 1067 | Entry<K,V> e = lastReturned = entry; | ||
| 1068 | entry = e.next; | ||
| 1069 | return type == KEYS ? (T)e.key : (type == VALUES ? (T)e.value : (T)e); | ||
| 1070 | } | ||
| 1071 | throw new NoSuchElementException("Hashtable Enumerator"); | ||
| 1072 | } | ||
| 1073 | |||
| 1074 | // Iterator methods | ||
| 1075 | public boolean hasNext() { | ||
| 1076 | return hasMoreElements(); | ||
| 1077 | } | ||
| 1078 | |||
| 1079 | public T next() { | ||
| 1080 | if (modCount != expectedModCount) | ||
| 1081 | throw new ConcurrentModificationException(); | ||
| 1082 | return nextElement(); | ||
| 1083 | } | ||
| 1084 | |||
| 1085 | public void remove() { | ||
| 1086 | if (!iterator) | ||
| 1087 | throw new UnsupportedOperationException(); | ||
| 1088 | if (lastReturned == null) | ||
| 1089 | throw new IllegalStateException("Hashtable Enumerator"); | ||
| 1090 | if (modCount != expectedModCount) | ||
| 1091 | throw new ConcurrentModificationException(); | ||
| 1092 | |||
| 1093 | synchronized(Hashtable.this) { | ||
| 1094 | Entry[] tab = Hashtable.this.table; | ||
| 1095 | int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length; | ||
| 1096 | |||
| 1097 | for (Entry<K,V> e = tab[index], prev = null; e != null; | ||
| 1098 | prev = e, e = e.next) { | ||
| 1099 | if (e == lastReturned) { | ||
| 1100 | modCount++; | ||
| 1101 | expectedModCount++; | ||
| 1102 | if (prev == null) | ||
| 1103 | tab[index] = e.next; | ||
| 1104 | else | ||
| 1105 | prev.next = e.next; | ||
| 1106 | count--; | ||
| 1107 | lastReturned = null; | ||
| 1108 | return; | ||
| 1109 | } | ||
| 1110 | } | ||
| 1111 | throw new ConcurrentModificationException(); | ||
| 1112 | } | ||
| 1113 | } | ||
| 1114 | } | ||
| 1115 | } | ||