1 /*
2 * Copyright (c) 1994, 2018, 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
28 import java.io.*;
29 import java.util.function.BiConsumer;
30 import java.util.function.Function;
31 import java.util.function.BiFunction;
32 import jdk.internal.access.SharedSecrets;
33
34 /**
35 * This class implements a hash table, which maps keys to values. Any
36 * non-{@code null} object can be used as a key or as a value. <p>
37 *
38 * To successfully store and retrieve objects from a hashtable, the
39 * objects used as keys must implement the {@code hashCode}
40 * method and the {@code equals} method. <p>
41 *
42 * An instance of {@code Hashtable} has two parameters that affect its
43 * performance: <i>initial capacity</i> and <i>load factor</i>. The
44 * <i>capacity</i> is the number of <i>buckets</i> in the hash table, and the
45 * <i>initial capacity</i> is simply the capacity at the time the hash table
46 * is created. Note that the hash table is <i>open</i>: in the case of a "hash
47 * collision", a single bucket stores multiple entries, which must be searched
48 * sequentially. The <i>load factor</i> is a measure of how full the hash
49 * table is allowed to get before its capacity is automatically increased.
50 * The initial capacity and load factor parameters are merely hints to
51 * the implementation. The exact details as to when and whether the rehash
52 * method is invoked are implementation-dependent.<p>
53 *
54 * Generally, the default load factor (.75) offers a good tradeoff between
55 * time and space costs. Higher values decrease the space overhead but
56 * increase the time cost to look up an entry (which is reflected in most
57 * {@code Hashtable} operations, including {@code get} and {@code put}).<p>
58 *
59 * The initial capacity controls a tradeoff between wasted space and the
60 * need for {@code rehash} operations, which are time-consuming.
61 * No {@code rehash} operations will <i>ever</i> occur if the initial
62 * capacity is greater than the maximum number of entries the
63 * {@code Hashtable} will contain divided by its load factor. However,
64 * setting the initial capacity too high can waste space.<p>
65 *
66 * If many entries are to be made into a {@code Hashtable},
67 * creating it with a sufficiently large capacity may allow the
68 * entries to be inserted more efficiently than letting it perform
69 * automatic rehashing as needed to grow the table. <p>
70 *
71 * This example creates a hashtable of numbers. It uses the names of
72 * the numbers as keys:
73 * <pre> {@code
74 * Hashtable<String, Integer> numbers
75 * = new Hashtable<String, Integer>();
76 * numbers.put("one", 1);
77 * numbers.put("two", 2);
78 * numbers.put("three", 3);}</pre>
79 *
80 * <p>To retrieve a number, use the following code:
81 * <pre> {@code
82 * Integer n = numbers.get("two");
83 * if (n != null) {
84 * System.out.println("two = " + n);
85 * }}</pre>
86 *
87 * <p>The iterators returned by the {@code iterator} method of the collections
88 * returned by all of this class's "collection view methods" are
89 * <em>fail-fast</em>: if the Hashtable is structurally modified at any time
90 * after the iterator is created, in any way except through the iterator's own
91 * {@code remove} method, the iterator will throw a {@link
92 * ConcurrentModificationException}. Thus, in the face of concurrent
93 * modification, the iterator fails quickly and cleanly, rather than risking
94 * arbitrary, non-deterministic behavior at an undetermined time in the future.
95 * The Enumerations returned by Hashtable's {@link #keys keys} and
96 * {@link #elements elements} methods are <em>not</em> fail-fast; if the
97 * Hashtable is structurally modified at any time after the enumeration is
98 * created then the results of enumerating are undefined.
99 *
100 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
101 * as it is, generally speaking, impossible to make any hard guarantees in the
102 * presence of unsynchronized concurrent modification. Fail-fast iterators
103 * throw {@code ConcurrentModificationException} on a best-effort basis.
104 * Therefore, it would be wrong to write a program that depended on this
105 * exception for its correctness: <i>the fail-fast behavior of iterators
106 * should be used only to detect bugs.</i>
107 *
108 * <p>As of the Java 2 platform v1.2, this class was retrofitted to
109 * implement the {@link Map} interface, making it a member of the
110 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
111 *
112 * Java Collections Framework</a>. Unlike the new collection
113 * implementations, {@code Hashtable} is synchronized. If a
114 * thread-safe implementation is not needed, it is recommended to use
115 * {@link HashMap} in place of {@code Hashtable}. If a thread-safe
116 * highly-concurrent implementation is desired, then it is recommended
117 * to use {@link java.util.concurrent.ConcurrentHashMap} in place of
118 * {@code Hashtable}.
119 *
120 * @param <K> the type of keys maintained by this map
121 * @param <V> the type of mapped values
122 *
123 * @author Arthur van Hoff
124 * @author Josh Bloch
125 * @author Neal Gafter
126 * @see Object#equals(java.lang.Object)
127 * @see Object#hashCode()
128 * @see Hashtable#rehash()
129 * @see Collection
130 * @see Map
131 * @see HashMap
132 * @see TreeMap
133 * @since 1.0
134 */
135 public class Hashtable<K,V>
136 extends Dictionary<K,V>
137 implements Map<K,V>, Cloneable, java.io.Serializable {
138
139 /**
140 * The hash table data.
141 */
142 private transient Entry<?,?>[] table;
143
144 /**
145 * The total number of entries in the hash table.
146 */
147 private transient int count;
148
149 /**
150 * The table is rehashed when its size exceeds this threshold. (The
151 * value of this field is (int)(capacity * loadFactor).)
152 *
153 * @serial
154 */
155 private int threshold;
156
157 /**
158 * The load factor for the hashtable.
159 *
160 * @serial
161 */
162 private float loadFactor;
163
164 /**
165 * The number of times this Hashtable has been structurally modified
166 * Structural modifications are those that change the number of entries in
167 * the Hashtable or otherwise modify its internal structure (e.g.,
168 * rehash). This field is used to make iterators on Collection-views of
169 * the Hashtable fail-fast. (See ConcurrentModificationException).
170 */
171 private transient int modCount = 0;
172
173 /** use serialVersionUID from JDK 1.0.2 for interoperability */
174 private static final long serialVersionUID = 1421746759512286392L;
175
176 /**
177 * Constructs a new, empty hashtable with the specified initial
178 * capacity and the specified load factor.
179 *
180 * @param initialCapacity the initial capacity of the hashtable.
181 * @param loadFactor the load factor of the hashtable.
182 * @exception IllegalArgumentException if the initial capacity is less
183 * than zero, or if the load factor is nonpositive.
184 */
185 public Hashtable(int initialCapacity, float loadFactor) {
186 if (initialCapacity < 0)
187 throw new IllegalArgumentException("Illegal Capacity: " +
188 initialCapacity);
189 if (!(loadFactor > 0)) // also checks for NaNs
190 throw new IllegalArgumentException("Illegal load factor: " +
191 loadFactor);
192
193 if (initialCapacity==0)
194 initialCapacity = 1;
195 this.loadFactor = loadFactor;
196 table = new Entry<?,?>[initialCapacity];
197 threshold = (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
198 }
199
200 /**
201 * Constructs a new, empty hashtable with the specified initial capacity
202 * and default load factor (0.75).
203 *
204 * @param initialCapacity the initial capacity of the hashtable.
205 * @exception IllegalArgumentException if the initial capacity is less
206 * than zero.
207 */
208 public Hashtable(int initialCapacity) {
209 this(initialCapacity, 0.75f);
210 }
211
212 /**
213 * Constructs a new, empty hashtable with a default initial capacity (11)
214 * and load factor (0.75).
215 */
216 public Hashtable() {
217 this(11, 0.75f);
218 }
219
220 /**
221 * Constructs a new hashtable with the same mappings as the given
222 * Map. The hashtable is created with an initial capacity sufficient to
223 * hold the mappings in the given Map and a default load factor (0.75).
224 *
225 * @param t the map whose mappings are to be placed in this map.
226 * @throws NullPointerException if the specified map is null.
227 * @since 1.2
228 */
229 public Hashtable(Map<? extends K, ? extends V> t) {
230 this(Math.max(2*t.size(), 11), 0.75f);
231 putAll(t);
232 }
233
234 /**
235 * A constructor chained from {@link Properties} keeps Hashtable fields
236 * uninitialized since they are not used.
237 *
238 * @param dummy a dummy parameter
239 */
240 Hashtable(Void dummy) {}
241
242 /**
243 * Returns the number of keys in this hashtable.
244 *
245 * @return the number of keys in this hashtable.
246 */
247 public synchronized int size() {
248 return count;
249 }
250
251 /**
252 * Tests if this hashtable maps no keys to values.
253 *
254 * @return {@code true} if this hashtable maps no keys to values;
255 * {@code false} otherwise.
256 */
257 public synchronized boolean isEmpty() {
258 return count == 0;
259 }
260
261 /**
262 * Returns an enumeration of the keys in this hashtable.
263 * Use the Enumeration methods on the returned object to fetch the keys
264 * sequentially. If the hashtable is structurally modified while enumerating
265 * over the keys then the results of enumerating are undefined.
266 *
267 * @return an enumeration of the keys in this hashtable.
268 * @see Enumeration
269 * @see #elements()
270 * @see #keySet()
271 * @see Map
272 */
273 public synchronized Enumeration<K> keys() {
274 return this.<K>getEnumeration(KEYS);
275 }
276
277 /**
278 * Returns an enumeration of the values in this hashtable.
279 * Use the Enumeration methods on the returned object to fetch the elements
280 * sequentially. If the hashtable is structurally modified while enumerating
281 * over the values then the results of enumerating are undefined.
282 *
283 * @return an enumeration of the values in this hashtable.
284 * @see java.util.Enumeration
285 * @see #keys()
286 * @see #values()
287 * @see Map
288 */
289 public synchronized Enumeration<V> elements() {
290 return this.<V>getEnumeration(VALUES);
291 }
292
293 /**
294 * Tests if some key maps into the specified value in this hashtable.
295 * This operation is more expensive than the {@link #containsKey
296 * containsKey} method.
297 *
298 * <p>Note that this method is identical in functionality to
299 * {@link #containsValue containsValue}, (which is part of the
300 * {@link Map} interface in the collections framework).
301 *
302 * @param value a value to search for
303 * @return {@code true} if and only if some key maps to the
304 * {@code value} argument in this hashtable as
305 * determined by the {@code equals} method;
306 * {@code false} otherwise.
307 * @exception NullPointerException if the value is {@code null}
308 */
309 public synchronized boolean contains(Object value) {
310 if (value == null) {
311 throw new NullPointerException();
312 }
313
314 Entry<?,?> tab[] = table;
315 for (int i = tab.length ; i-- > 0 ;) {
316 for (Entry<?,?> e = tab[i] ; e != null ; e = e.next) {
317 if (e.value.equals(value)) {
318 return true;
319 }
320 }
321 }
322 return false;
323 }
324
325 /**
326 * Returns true if this hashtable maps one or more keys to this value.
327 *
328 * <p>Note that this method is identical in functionality to {@link
329 * #contains contains} (which predates the {@link Map} interface).
330 *
331 * @param value value whose presence in this hashtable is to be tested
332 * @return {@code true} if this map maps one or more keys to the
333 * specified value
334 * @throws NullPointerException if the value is {@code null}
335 * @since 1.2
336 */
337 public boolean containsValue(Object value) {
338 return contains(value);
339 }
340
341 /**
342 * Tests if the specified object is a key in this hashtable.
343 *
344 * @param key possible key
345 * @return {@code true} if and only if the specified object
346 * is a key in this hashtable, as determined by the
347 * {@code equals} method; {@code false} otherwise.
348 * @throws NullPointerException if the key is {@code null}
349 * @see #contains(Object)
350 */
351 public synchronized boolean containsKey(Object key) {
352 Entry<?,?> tab[] = table;
353 int hash = key.hashCode();
354 int index = (hash & 0x7FFFFFFF) % tab.length;
355 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
356 if ((e.hash == hash) && e.key.equals(key)) {
357 return true;
358 }
359 }
360 return false;
361 }
362
363 /**
364 * Returns the value to which the specified key is mapped,
365 * or {@code null} if this map contains no mapping for the key.
366 *
367 * <p>More formally, if this map contains a mapping from a key
368 * {@code k} to a value {@code v} such that {@code (key.equals(k))},
369 * then this method returns {@code v}; otherwise it returns
370 * {@code null}. (There can be at most one such mapping.)
371 *
372 * @param key the key whose associated value is to be returned
373 * @return the value to which the specified key is mapped, or
374 * {@code null} if this map contains no mapping for the key
375 * @throws NullPointerException if the specified key is null
376 * @see #put(Object, Object)
377 */
378 @SuppressWarnings("unchecked")
379 public synchronized V get(Object key) {
380 Entry<?,?> tab[] = table;
381 int hash = key.hashCode();
382 int index = (hash & 0x7FFFFFFF) % tab.length;
383 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
384 if ((e.hash == hash) && e.key.equals(key)) {
385 return (V)e.value;
386 }
387 }
388 return null;
389 }
390
391 /**
392 * The maximum size of array to allocate.
393 * Some VMs reserve some header words in an array.
394 * Attempts to allocate larger arrays may result in
395 * OutOfMemoryError: Requested array size exceeds VM limit
396 */
397 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
398
399 /**
400 * Increases the capacity of and internally reorganizes this
401 * hashtable, in order to accommodate and access its entries more
402 * efficiently. This method is called automatically when the
403 * number of keys in the hashtable exceeds this hashtable's capacity
404 * and load factor.
405 */
406 @SuppressWarnings("unchecked")
407 protected void rehash() {
408 int oldCapacity = table.length;
409 Entry<?,?>[] oldMap = table;
410
411 // overflow-conscious code
412 int newCapacity = (oldCapacity << 1) + 1;
413 if (newCapacity - MAX_ARRAY_SIZE > 0) {
414 if (oldCapacity == MAX_ARRAY_SIZE)
415 // Keep running with MAX_ARRAY_SIZE buckets
416 return;
417 newCapacity = MAX_ARRAY_SIZE;
418 }
419 Entry<?,?>[] newMap = new Entry<?,?>[newCapacity];
420
421 modCount++;
422 threshold = (int)Math.min(newCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
423 table = newMap;
424
425 for (int i = oldCapacity ; i-- > 0 ;) {
426 for (Entry<K,V> old = (Entry<K,V>)oldMap[i] ; old != null ; ) {
427 Entry<K,V> e = old;
428 old = old.next;
429
430 int index = (e.hash & 0x7FFFFFFF) % newCapacity;
431 e.next = (Entry<K,V>)newMap[index];
432 newMap[index] = e;
433 }
434 }
435 }
436
437 private void addEntry(int hash, K key, V value, int index) {
438 Entry<?,?> tab[] = table;
439 if (count >= threshold) {
440 // Rehash the table if the threshold is exceeded
441 rehash();
442
443 tab = table;
444 hash = key.hashCode();
445 index = (hash & 0x7FFFFFFF) % tab.length;
446 }
447
448 // Creates the new entry.
449 @SuppressWarnings("unchecked")
450 Entry<K,V> e = (Entry<K,V>) tab[index];
451 tab[index] = new Entry<>(hash, key, value, e);
452 count++;
453 modCount++;
454 }
455
456 /**
457 * Maps the specified {@code key} to the specified
458 * {@code value} in this hashtable. Neither the key nor the
459 * value can be {@code null}. <p>
460 *
461 * The value can be retrieved by calling the {@code get} method
462 * with a key that is equal to the original key.
463 *
464 * @param key the hashtable key
465 * @param value the value
466 * @return the previous value of the specified key in this hashtable,
467 * or {@code null} if it did not have one
468 * @exception NullPointerException if the key or value is
469 * {@code null}
470 * @see Object#equals(Object)
471 * @see #get(Object)
472 */
473 public synchronized V put(K key, V value) {
474 // Make sure the value is not null
475 if (value == null) {
476 throw new NullPointerException();
477 }
478
479 // Makes sure the key is not already in the hashtable.
480 Entry<?,?> tab[] = table;
481 int hash = key.hashCode();
482 int index = (hash & 0x7FFFFFFF) % tab.length;
483 @SuppressWarnings("unchecked")
484 Entry<K,V> entry = (Entry<K,V>)tab[index];
485 for(; entry != null ; entry = entry.next) {
486 if ((entry.hash == hash) && entry.key.equals(key)) {
487 V old = entry.value;
488 entry.value = value;
489 return old;
490 }
491 }
492
493 addEntry(hash, key, value, index);
494 return null;
495 }
496
497 /**
498 * Removes the key (and its corresponding value) from this
499 * hashtable. This method does nothing if the key is not in the hashtable.
500 *
501 * @param key the key that needs to be removed
502 * @return the value to which the key had been mapped in this hashtable,
503 * or {@code null} if the key did not have a mapping
504 * @throws NullPointerException if the key is {@code null}
505 */
506 public synchronized V remove(Object key) {
507 Entry<?,?> tab[] = table;
508 int hash = key.hashCode();
509 int index = (hash & 0x7FFFFFFF) % tab.length;
510 @SuppressWarnings("unchecked")
511 Entry<K,V> e = (Entry<K,V>)tab[index];
512 for(Entry<K,V> prev = null ; e != null ; prev = e, e = e.next) {
513 if ((e.hash == hash) && e.key.equals(key)) {
514 if (prev != null) {
515 prev.next = e.next;
516 } else {
517 tab[index] = e.next;
518 }
519 modCount++;
520 count--;
521 V oldValue = e.value;
522 e.value = null;
523 return oldValue;
524 }
525 }
526 return null;
527 }
528
529 /**
530 * Copies all of the mappings from the specified map to this hashtable.
531 * These mappings will replace any mappings that this hashtable had for any
532 * of the keys currently in the specified map.
533 *
534 * @param t mappings to be stored in this map
535 * @throws NullPointerException if the specified map is null
536 * @since 1.2
537 */
538 public synchronized void putAll(Map<? extends K, ? extends V> t) {
539 for (Map.Entry<? extends K, ? extends V> e : t.entrySet())
540 put(e.getKey(), e.getValue());
541 }
542
543 /**
544 * Clears this hashtable so that it contains no keys.
545 */
546 public synchronized void clear() {
547 Entry<?,?> tab[] = table;
548 for (int index = tab.length; --index >= 0; )
549 tab[index] = null;
550 modCount++;
551 count = 0;
552 }
553
554 /**
555 * Creates a shallow copy of this hashtable. All the structure of the
556 * hashtable itself is copied, but the keys and values are not cloned.
557 * This is a relatively expensive operation.
558 *
559 * @return a clone of the hashtable
560 */
561 public synchronized Object clone() {
562 Hashtable<?,?> t = cloneHashtable();
563 t.table = new Entry<?,?>[table.length];
564 for (int i = table.length ; i-- > 0 ; ) {
565 t.table[i] = (table[i] != null)
566 ? (Entry<?,?>) table[i].clone() : null;
567 }
568 t.keySet = null;
569 t.entrySet = null;
570 t.values = null;
571 t.modCount = 0;
572 return t;
573 }
574
575 /** Calls super.clone() */
576 final Hashtable<?,?> cloneHashtable() {
577 try {
578 return (Hashtable<?,?>)super.clone();
579 } catch (CloneNotSupportedException e) {
580 // this shouldn't happen, since we are Cloneable
581 throw new InternalError(e);
582 }
583 }
584
585 /**
586 * Returns a string representation of this {@code Hashtable} object
587 * in the form of a set of entries, enclosed in braces and separated
588 * by the ASCII characters "<code> , </code>" (comma and space). Each
589 * entry is rendered as the key, an equals sign {@code =}, and the
590 * associated element, where the {@code toString} method is used to
591 * convert the key and element to strings.
592 *
593 * @return a string representation of this hashtable
594 */
595 public synchronized String toString() {
596 int max = size() - 1;
597 if (max == -1)
598 return "{}";
599
600 StringBuilder sb = new StringBuilder();
601 Iterator<Map.Entry<K,V>> it = entrySet().iterator();
602
603 sb.append('{');
604 for (int i = 0; ; i++) {
605 Map.Entry<K,V> e = it.next();
606 K key = e.getKey();
607 V value = e.getValue();
608 sb.append(key == this ? "(this Map)" : key.toString());
609 sb.append('=');
610 sb.append(value == this ? "(this Map)" : value.toString());
611
612 if (i == max)
613 return sb.append('}').toString();
614 sb.append(", ");
615 }
616 }
617
618
619 private <T> Enumeration<T> getEnumeration(int type) {
620 if (count == 0) {
621 return Collections.emptyEnumeration();
622 } else {
623 return new Enumerator<>(type, false);
624 }
625 }
626
627 private <T> Iterator<T> getIterator(int type) {
628 if (count == 0) {
629 return Collections.emptyIterator();
630 } else {
631 return new Enumerator<>(type, true);
632 }
633 }
634
635 // Views
636
637 /**
638 * Each of these fields are initialized to contain an instance of the
639 * appropriate view the first time this view is requested. The views are
640 * stateless, so there's no reason to create more than one of each.
641 */
642 private transient volatile Set<K> keySet;
643 private transient volatile Set<Map.Entry<K,V>> entrySet;
644 private transient volatile Collection<V> values;
645
646 /**
647 * Returns a {@link Set} view of the keys contained in this map.
648 * The set is backed by the map, so changes to the map are
649 * reflected in the set, and vice-versa. If the map is modified
650 * while an iteration over the set is in progress (except through
651 * the iterator's own {@code remove} operation), the results of
652 * the iteration are undefined. The set supports element removal,
653 * which removes the corresponding mapping from the map, via the
654 * {@code Iterator.remove}, {@code Set.remove},
655 * {@code removeAll}, {@code retainAll}, and {@code clear}
656 * operations. It does not support the {@code add} or {@code addAll}
657 * operations.
658 *
659 * @since 1.2
660 */
661 public Set<K> keySet() {
662 if (keySet == null)
663 keySet = Collections.synchronizedSet(new KeySet(), this);
664 return keySet;
665 }
666
667 private class KeySet extends AbstractSet<K> {
668 public Iterator<K> iterator() {
669 return getIterator(KEYS);
670 }
671 public int size() {
672 return count;
673 }
674 public boolean contains(Object o) {
675 return containsKey(o);
676 }
677 public boolean remove(Object o) {
678 return Hashtable.this.remove(o) != null;
679 }
680 public void clear() {
681 Hashtable.this.clear();
682 }
683 }
684
685 /**
686 * Returns a {@link Set} view of the mappings contained in this map.
687 * The set is backed by the map, so changes to the map are
688 * reflected in the set, and vice-versa. If the map is modified
689 * while an iteration over the set is in progress (except through
690 * the iterator's own {@code remove} operation, or through the
691 * {@code setValue} operation on a map entry returned by the
692 * iterator) the results of the iteration are undefined. The set
693 * supports element removal, which removes the corresponding
694 * mapping from the map, via the {@code Iterator.remove},
695 * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
696 * {@code clear} operations. It does not support the
697 * {@code add} or {@code addAll} operations.
698 *
699 * @since 1.2
700 */
701 public Set<Map.Entry<K,V>> entrySet() {
702 if (entrySet==null)
703 entrySet = Collections.synchronizedSet(new EntrySet(), this);
704 return entrySet;
705 }
706
707 private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
708 public Iterator<Map.Entry<K,V>> iterator() {
709 return getIterator(ENTRIES);
710 }
711
712 public boolean add(Map.Entry<K,V> o) {
713 return super.add(o);
714 }
715
716 public boolean contains(Object o) {
717 if (!(o instanceof Map.Entry))
718 return false;
719 Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
720 Object key = entry.getKey();
721 Entry<?,?>[] tab = table;
722 int hash = key.hashCode();
723 int index = (hash & 0x7FFFFFFF) % tab.length;
724
725 for (Entry<?,?> e = tab[index]; e != null; e = e.next)
726 if (e.hash==hash && e.equals(entry))
727 return true;
728 return false;
729 }
730
731 public boolean remove(Object o) {
732 if (!(o instanceof Map.Entry))
733 return false;
734 Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
735 Object key = entry.getKey();
736 Entry<?,?>[] tab = table;
737 int hash = key.hashCode();
738 int index = (hash & 0x7FFFFFFF) % tab.length;
739
740 @SuppressWarnings("unchecked")
741 Entry<K,V> e = (Entry<K,V>)tab[index];
742 for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
743 if (e.hash==hash && e.equals(entry)) {
744 if (prev != null)
745 prev.next = e.next;
746 else
747 tab[index] = e.next;
748
749 e.value = null; // clear for gc.
750 modCount++;
751 count--;
752 return true;
753 }
754 }
755 return false;
756 }
757
758 public int size() {
759 return count;
760 }
761
762 public void clear() {
763 Hashtable.this.clear();
764 }
765 }
766
767 /**
768 * Returns a {@link Collection} view of the values contained in this map.
769 * The collection is backed by the map, so changes to the map are
770 * reflected in the collection, and vice-versa. If the map is
771 * modified while an iteration over the collection is in progress
772 * (except through the iterator's own {@code remove} operation),
773 * the results of the iteration are undefined. The collection
774 * supports element removal, which removes the corresponding
775 * mapping from the map, via the {@code Iterator.remove},
776 * {@code Collection.remove}, {@code removeAll},
777 * {@code retainAll} and {@code clear} operations. It does not
778 * support the {@code add} or {@code addAll} operations.
779 *
780 * @since 1.2
781 */
782 public Collection<V> values() {
783 if (values==null)
784 values = Collections.synchronizedCollection(new ValueCollection(),
785 this);
786 return values;
787 }
788
789 private class ValueCollection extends AbstractCollection<V> {
790 public Iterator<V> iterator() {
791 return getIterator(VALUES);
792 }
793 public int size() {
794 return count;
795 }
796 public boolean contains(Object o) {
797 return containsValue(o);
798 }
799 public void clear() {
800 Hashtable.this.clear();
801 }
802 }
803
804 // Comparison and hashing
805
806 /**
807 * Compares the specified Object with this Map for equality,
808 * as per the definition in the Map interface.
809 *
810 * @param o object to be compared for equality with this hashtable
811 * @return true if the specified Object is equal to this Map
812 * @see Map#equals(Object)
813 * @since 1.2
814 */
815 public synchronized boolean equals(Object o) {
816 if (o == this)
817 return true;
818
819 if (!(o instanceof Map))
820 return false;
821 Map<?,?> t = (Map<?,?>) o;
822 if (t.size() != size())
823 return false;
824
825 try {
826 for (Map.Entry<K, V> e : entrySet()) {
827 K key = e.getKey();
828 V value = e.getValue();
829 if (value == null) {
830 if (!(t.get(key) == null && t.containsKey(key)))
831 return false;
832 } else {
833 if (!value.equals(t.get(key)))
834 return false;
835 }
836 }
837 } catch (ClassCastException unused) {
838 return false;
839 } catch (NullPointerException unused) {
840 return false;
841 }
842
843 return true;
844 }
845
846 /**
847 * Returns the hash code value for this Map as per the definition in the
848 * Map interface.
849 *
850 * @see Map#hashCode()
851 * @since 1.2
852 */
853 public synchronized int hashCode() {
854 /*
855 * This code detects the recursion caused by computing the hash code
856 * of a self-referential hash table and prevents the stack overflow
857 * that would otherwise result. This allows certain 1.1-era
858 * applets with self-referential hash tables to work. This code
859 * abuses the loadFactor field to do double-duty as a hashCode
860 * in progress flag, so as not to worsen the space performance.
861 * A negative load factor indicates that hash code computation is
862 * in progress.
863 */
864 int h = 0;
865 if (count == 0 || loadFactor < 0)
866 return h; // Returns zero
867
868 loadFactor = -loadFactor; // Mark hashCode computation in progress
869 Entry<?,?>[] tab = table;
870 for (Entry<?,?> entry : tab) {
871 while (entry != null) {
872 h += entry.hashCode();
873 entry = entry.next;
874 }
875 }
876
877 loadFactor = -loadFactor; // Mark hashCode computation complete
878
879 return h;
880 }
881
882 @Override
883 public synchronized V getOrDefault(Object key, V defaultValue) {
884 V result = get(key);
885 return (null == result) ? defaultValue : result;
886 }
887
888 @SuppressWarnings("unchecked")
889 @Override
890 public synchronized void forEach(BiConsumer<? super K, ? super V> action) {
891 Objects.requireNonNull(action); // explicit check required in case
892 // table is empty.
893 final int expectedModCount = modCount;
894
895 Entry<?, ?>[] tab = table;
896 for (Entry<?, ?> entry : tab) {
897 while (entry != null) {
898 action.accept((K)entry.key, (V)entry.value);
899 entry = entry.next;
900
901 if (expectedModCount != modCount) {
902 throw new ConcurrentModificationException();
903 }
904 }
905 }
906 }
907
908 @SuppressWarnings("unchecked")
909 @Override
910 public synchronized void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
911 Objects.requireNonNull(function); // explicit check required in case
912 // table is empty.
913 final int expectedModCount = modCount;
914
915 Entry<K, V>[] tab = (Entry<K, V>[])table;
916 for (Entry<K, V> entry : tab) {
917 while (entry != null) {
918 entry.value = Objects.requireNonNull(
919 function.apply(entry.key, entry.value));
920 entry = entry.next;
921
922 if (expectedModCount != modCount) {
923 throw new ConcurrentModificationException();
924 }
925 }
926 }
927 }
928
929 @Override
930 public synchronized V putIfAbsent(K key, V value) {
931 Objects.requireNonNull(value);
932
933 // Makes sure the key is not already in the hashtable.
934 Entry<?,?> tab[] = table;
935 int hash = key.hashCode();
936 int index = (hash & 0x7FFFFFFF) % tab.length;
937 @SuppressWarnings("unchecked")
938 Entry<K,V> entry = (Entry<K,V>)tab[index];
939 for (; entry != null; entry = entry.next) {
940 if ((entry.hash == hash) && entry.key.equals(key)) {
941 V old = entry.value;
942 if (old == null) {
943 entry.value = value;
944 }
945 return old;
946 }
947 }
948
949 addEntry(hash, key, value, index);
950 return null;
951 }
952
953 @Override
954 public synchronized boolean remove(Object key, Object value) {
955 Objects.requireNonNull(value);
956
957 Entry<?,?> tab[] = table;
958 int hash = key.hashCode();
959 int index = (hash & 0x7FFFFFFF) % tab.length;
960 @SuppressWarnings("unchecked")
961 Entry<K,V> e = (Entry<K,V>)tab[index];
962 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
963 if ((e.hash == hash) && e.key.equals(key) && e.value.equals(value)) {
964 if (prev != null) {
965 prev.next = e.next;
966 } else {
967 tab[index] = e.next;
968 }
969 e.value = null; // clear for gc
970 modCount++;
971 count--;
972 return true;
973 }
974 }
975 return false;
976 }
977
978 @Override
979 public synchronized boolean replace(K key, V oldValue, V newValue) {
980 Objects.requireNonNull(oldValue);
981 Objects.requireNonNull(newValue);
982 Entry<?,?> tab[] = table;
983 int hash = key.hashCode();
984 int index = (hash & 0x7FFFFFFF) % tab.length;
985 @SuppressWarnings("unchecked")
986 Entry<K,V> e = (Entry<K,V>)tab[index];
987 for (; e != null; e = e.next) {
988 if ((e.hash == hash) && e.key.equals(key)) {
989 if (e.value.equals(oldValue)) {
990 e.value = newValue;
991 return true;
992 } else {
993 return false;
994 }
995 }
996 }
997 return false;
998 }
999
1000 @Override
1001 public synchronized V replace(K key, V value) {
1002 Objects.requireNonNull(value);
1003 Entry<?,?> tab[] = table;
1004 int hash = key.hashCode();
1005 int index = (hash & 0x7FFFFFFF) % tab.length;
1006 @SuppressWarnings("unchecked")
1007 Entry<K,V> e = (Entry<K,V>)tab[index];
1008 for (; e != null; e = e.next) {
1009 if ((e.hash == hash) && e.key.equals(key)) {
1010 V oldValue = e.value;
1011 e.value = value;
1012 return oldValue;
1013 }
1014 }
1015 return null;
1016 }
1017
1018 /**
1019 * {@inheritDoc}
1020 *
1021 * <p>This method will, on a best-effort basis, throw a
1022 * {@link java.util.ConcurrentModificationException} if the mapping
1023 * function modified this map during computation.
1024 *
1025 * @throws ConcurrentModificationException if it is detected that the
1026 * mapping function modified this map
1027 */
1028 @Override
1029 public synchronized V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1030 Objects.requireNonNull(mappingFunction);
1031
1032 Entry<?,?> tab[] = table;
1033 int hash = key.hashCode();
1034 int index = (hash & 0x7FFFFFFF) % tab.length;
1035 @SuppressWarnings("unchecked")
1036 Entry<K,V> e = (Entry<K,V>)tab[index];
1037 for (; e != null; e = e.next) {
1038 if (e.hash == hash && e.key.equals(key)) {
1039 // Hashtable not accept null value
1040 return e.value;
1041 }
1042 }
1043
1044 int mc = modCount;
1045 V newValue = mappingFunction.apply(key);
1046 if (mc != modCount) { throw new ConcurrentModificationException(); }
1047 if (newValue != null) {
1048 addEntry(hash, key, newValue, index);
1049 }
1050
1051 return newValue;
1052 }
1053
1054 /**
1055 * {@inheritDoc}
1056 *
1057 * <p>This method will, on a best-effort basis, throw a
1058 * {@link java.util.ConcurrentModificationException} if the remapping
1059 * function modified this map during computation.
1060 *
1061 * @throws ConcurrentModificationException if it is detected that the
1062 * remapping function modified this map
1063 */
1064 @Override
1065 public synchronized V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1066 Objects.requireNonNull(remappingFunction);
1067
1068 Entry<?,?> tab[] = table;
1069 int hash = key.hashCode();
1070 int index = (hash & 0x7FFFFFFF) % tab.length;
1071 @SuppressWarnings("unchecked")
1072 Entry<K,V> e = (Entry<K,V>)tab[index];
1073 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1074 if (e.hash == hash && e.key.equals(key)) {
1075 int mc = modCount;
1076 V newValue = remappingFunction.apply(key, e.value);
1077 if (mc != modCount) {
1078 throw new ConcurrentModificationException();
1079 }
1080 if (newValue == null) {
1081 if (prev != null) {
1082 prev.next = e.next;
1083 } else {
1084 tab[index] = e.next;
1085 }
1086 modCount = mc + 1;
1087 count--;
1088 } else {
1089 e.value = newValue;
1090 }
1091 return newValue;
1092 }
1093 }
1094 return null;
1095 }
1096 /**
1097 * {@inheritDoc}
1098 *
1099 * <p>This method will, on a best-effort basis, throw a
1100 * {@link java.util.ConcurrentModificationException} if the remapping
1101 * function modified this map during computation.
1102 *
1103 * @throws ConcurrentModificationException if it is detected that the
1104 * remapping function modified this map
1105 */
1106 @Override
1107 public synchronized V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1108 Objects.requireNonNull(remappingFunction);
1109
1110 Entry<?,?> tab[] = table;
1111 int hash = key.hashCode();
1112 int index = (hash & 0x7FFFFFFF) % tab.length;
1113 @SuppressWarnings("unchecked")
1114 Entry<K,V> e = (Entry<K,V>)tab[index];
1115 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1116 if (e.hash == hash && Objects.equals(e.key, key)) {
1117 int mc = modCount;
1118 V newValue = remappingFunction.apply(key, e.value);
1119 if (mc != modCount) {
1120 throw new ConcurrentModificationException();
1121 }
1122 if (newValue == null) {
1123 if (prev != null) {
1124 prev.next = e.next;
1125 } else {
1126 tab[index] = e.next;
1127 }
1128 modCount = mc + 1;
1129 count--;
1130 } else {
1131 e.value = newValue;
1132 }
1133 return newValue;
1134 }
1135 }
1136
1137 int mc = modCount;
1138 V newValue = remappingFunction.apply(key, null);
1139 if (mc != modCount) { throw new ConcurrentModificationException(); }
1140 if (newValue != null) {
1141 addEntry(hash, key, newValue, index);
1142 }
1143
1144 return newValue;
1145 }
1146
1147 /**
1148 * {@inheritDoc}
1149 *
1150 * <p>This method will, on a best-effort basis, throw a
1151 * {@link java.util.ConcurrentModificationException} if the remapping
1152 * function modified this map during computation.
1153 *
1154 * @throws ConcurrentModificationException if it is detected that the
1155 * remapping function modified this map
1156 */
1157 @Override
1158 public synchronized V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1159 Objects.requireNonNull(remappingFunction);
1160
1161 Entry<?,?> tab[] = table;
1162 int hash = key.hashCode();
1163 int index = (hash & 0x7FFFFFFF) % tab.length;
1164 @SuppressWarnings("unchecked")
1165 Entry<K,V> e = (Entry<K,V>)tab[index];
1166 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1167 if (e.hash == hash && e.key.equals(key)) {
1168 int mc = modCount;
1169 V newValue = remappingFunction.apply(e.value, value);
1170 if (mc != modCount) {
1171 throw new ConcurrentModificationException();
1172 }
1173 if (newValue == null) {
1174 if (prev != null) {
1175 prev.next = e.next;
1176 } else {
1177 tab[index] = e.next;
1178 }
1179 modCount = mc + 1;
1180 count--;
1181 } else {
1182 e.value = newValue;
1183 }
1184 return newValue;
1185 }
1186 }
1187
1188 if (value != null) {
1189 addEntry(hash, key, value, index);
1190 }
1191
1192 return value;
1193 }
1194
1195 /**
1196 * Save the state of the Hashtable to a stream (i.e., serialize it).
1197 *
1198 * @serialData The <i>capacity</i> of the Hashtable (the length of the
1199 * bucket array) is emitted (int), followed by the
1200 * <i>size</i> of the Hashtable (the number of key-value
1201 * mappings), followed by the key (Object) and value (Object)
1202 * for each key-value mapping represented by the Hashtable
1203 * The key-value mappings are emitted in no particular order.
1204 */
1205 private void writeObject(java.io.ObjectOutputStream s)
1206 throws IOException {
1207 writeHashtable(s);
1208 }
1209
1210 /**
1211 * Perform serialization of the Hashtable to an ObjectOutputStream.
1212 * The Properties class overrides this method.
1213 */
1214 void writeHashtable(java.io.ObjectOutputStream s)
1215 throws IOException {
1216 Entry<Object, Object> entryStack = null;
1217
1218 synchronized (this) {
1219 // Write out the threshold and loadFactor
1220 s.defaultWriteObject();
1221
1222 // Write out the length and count of elements
1223 s.writeInt(table.length);
1224 s.writeInt(count);
1225
1226 // Stack copies of the entries in the table
1227 for (Entry<?, ?> entry : table) {
1228
1229 while (entry != null) {
1230 entryStack =
1231 new Entry<>(0, entry.key, entry.value, entryStack);
1232 entry = entry.next;
1233 }
1234 }
1235 }
1236
1237 // Write out the key/value objects from the stacked entries
1238 while (entryStack != null) {
1239 s.writeObject(entryStack.key);
1240 s.writeObject(entryStack.value);
1241 entryStack = entryStack.next;
1242 }
1243 }
1244
1245 /**
1246 * Called by Properties to write out a simulated threshold and loadfactor.
1247 */
1248 final void defaultWriteHashtable(java.io.ObjectOutputStream s, int length,
1249 float loadFactor) throws IOException {
1250 this.threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
1251 this.loadFactor = loadFactor;
1252 s.defaultWriteObject();
1253 }
1254
1255 /**
1256 * Reconstitute the Hashtable from a stream (i.e., deserialize it).
1257 */
1258 private void readObject(java.io.ObjectInputStream s)
1259 throws IOException, ClassNotFoundException {
1260 readHashtable(s);
1261 }
1262
1263 /**
1264 * Perform deserialization of the Hashtable from an ObjectInputStream.
1265 * The Properties class overrides this method.
1266 */
1267 void readHashtable(java.io.ObjectInputStream s)
1268 throws IOException, ClassNotFoundException {
1269 // Read in the threshold and loadFactor
1270 s.defaultReadObject();
1271
1272 // Validate loadFactor (ignore threshold - it will be re-computed)
1273 if (!(loadFactor > 0)) // also checks for NaNs
1274 throw new StreamCorruptedException("Illegal load factor: " +
1275 loadFactor);
1276
1277 // Read the original length of the array and number of elements
1278 int origlength = s.readInt();
1279 int elements = s.readInt();
1280
1281 // Validate # of elements
1282 if (elements < 0)
1283 throw new StreamCorruptedException("Illegal # of Elements: " + elements);
1284
1285 // Clamp original length to be more than elements / loadFactor
1286 // (this is the invariant enforced with auto-growth)
1287 origlength = Math.max(origlength, (int)(elements / loadFactor) + 1);
1288
1289 // Compute new length with a bit of room 5% + 3 to grow but
1290 // no larger than the clamped original length. Make the length
1291 // odd if it's large enough, this helps distribute the entries.
1292 // Guard against the length ending up zero, that's not valid.
1293 int length = (int)((elements + elements / 20) / loadFactor) + 3;
1294 if (length > elements && (length & 1) == 0)
1295 length--;
1296 length = Math.min(length, origlength);
1297
1298 if (length < 0) { // overflow
1299 length = origlength;
1300 }
1301
1302 // Check Map.Entry[].class since it's the nearest public type to
1303 // what we're actually creating.
1304 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Map.Entry[].class, length);
1305 table = new Entry<?,?>[length];
1306 threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
1307 count = 0;
1308
1309 // Read the number of elements and then all the key/value objects
1310 for (; elements > 0; elements--) {
1311 @SuppressWarnings("unchecked")
1312 K key = (K)s.readObject();
1313 @SuppressWarnings("unchecked")
1314 V value = (V)s.readObject();
1315 // sync is eliminated for performance
1316 reconstitutionPut(table, key, value);
1317 }
1318 }
1319
1320 /**
1321 * The put method used by readObject. This is provided because put
1322 * is overridable and should not be called in readObject since the
1323 * subclass will not yet be initialized.
1324 *
1325 * <p>This differs from the regular put method in several ways. No
1326 * checking for rehashing is necessary since the number of elements
1327 * initially in the table is known. The modCount is not incremented and
1328 * there's no synchronization because we are creating a new instance.
1329 * Also, no return value is needed.
1330 */
1331 private void reconstitutionPut(Entry<?,?>[] tab, K key, V value)
1332 throws StreamCorruptedException
1333 {
1334 if (value == null) {
1335 throw new java.io.StreamCorruptedException();
1336 }
1337 // Makes sure the key is not already in the hashtable.
1338 // This should not happen in deserialized version.
1339 int hash = key.hashCode();
1340 int index = (hash & 0x7FFFFFFF) % tab.length;
1341 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
1342 if ((e.hash == hash) && e.key.equals(key)) {
1343 throw new java.io.StreamCorruptedException();
1344 }
1345 }
1346 // Creates the new entry.
1347 @SuppressWarnings("unchecked")
1348 Entry<K,V> e = (Entry<K,V>)tab[index];
1349 tab[index] = new Entry<>(hash, key, value, e);
1350 count++;
1351 }
1352
1353 /**
1354 * Hashtable bucket collision list entry
1355 */
1356 private static class Entry<K,V> implements Map.Entry<K,V> {
1357 final int hash;
1358 final K key;
1359 V value;
1360 Entry<K,V> next;
1361
1362 protected Entry(int hash, K key, V value, Entry<K,V> next) {
1363 this.hash = hash;
1364 this.key = key;
1365 this.value = value;
1366 this.next = next;
1367 }
1368
1369 @SuppressWarnings("unchecked")
1370 protected Object clone() {
1371 return new Entry<>(hash, key, value,
1372 (next==null ? null : (Entry<K,V>) next.clone()));
1373 }
1374
1375 // Map.Entry Ops
1376
1377 public K getKey() {
1378 return key;
1379 }
1380
1381 public V getValue() {
1382 return value;
1383 }
1384
1385 public V setValue(V value) {
1386 if (value == null)
1387 throw new NullPointerException();
1388
1389 V oldValue = this.value;
1390 this.value = value;
1391 return oldValue;
1392 }
1393
1394 public boolean equals(Object o) {
1395 if (!(o instanceof Map.Entry))
1396 return false;
1397 Map.Entry<?,?> e = (Map.Entry<?,?>)o;
1398
1399 return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
1400 (value==null ? e.getValue()==null : value.equals(e.getValue()));
1401 }
1402
1403 public int hashCode() {
1404 return hash ^ Objects.hashCode(value);
1405 }
1406
1407 public String toString() {
1408 return key.toString()+"="+value.toString();
1409 }
1410 }
1411
1412 // Types of Enumerations/Iterations
1413 private static final int KEYS = 0;
1414 private static final int VALUES = 1;
1415 private static final int ENTRIES = 2;
1416
1417 /**
1418 * A hashtable enumerator class. This class implements both the
1419 * Enumeration and Iterator interfaces, but individual instances
1420 * can be created with the Iterator methods disabled. This is necessary
1421 * to avoid unintentionally increasing the capabilities granted a user
1422 * by passing an Enumeration.
1423 */
1424 private class Enumerator<T> implements Enumeration<T>, Iterator<T> {
1425 final Entry<?,?>[] table = Hashtable.this.table;
1426 int index = table.length;
1427 Entry<?,?> entry;
1428 Entry<?,?> lastReturned;
1429 final int type;
1430
1431 /**
1432 * Indicates whether this Enumerator is serving as an Iterator
1433 * or an Enumeration. (true -> Iterator).
1434 */
1435 final boolean iterator;
1436
1437 /**
1438 * The modCount value that the iterator believes that the backing
1439 * Hashtable should have. If this expectation is violated, the iterator
1440 * has detected concurrent modification.
1441 */
1442 protected int expectedModCount = Hashtable.this.modCount;
1443
1444 Enumerator(int type, boolean iterator) {
1445 this.type = type;
1446 this.iterator = iterator;
1447 }
1448
1449 public boolean hasMoreElements() {
1450 Entry<?,?> e = entry;
1451 int i = index;
1452 Entry<?,?>[] t = table;
1453 /* Use locals for faster loop iteration */
1454 while (e == null && i > 0) {
1455 e = t[--i];
1456 }
1457 entry = e;
1458 index = i;
1459 return e != null;
1460 }
1461
1462 @SuppressWarnings("unchecked")
1463 public T nextElement() {
1464 Entry<?,?> et = entry;
1465 int i = index;
1466 Entry<?,?>[] t = table;
1467 /* Use locals for faster loop iteration */
1468 while (et == null && i > 0) {
1469 et = t[--i];
1470 }
1471 entry = et;
1472 index = i;
1473 if (et != null) {
1474 Entry<?,?> e = lastReturned = entry;
1475 entry = e.next;
1476 return type == KEYS ? (T)e.key : (type == VALUES ? (T)e.value : (T)e);
1477 }
1478 throw new NoSuchElementException("Hashtable Enumerator");
1479 }
1480
1481 // Iterator methods
1482 public boolean hasNext() {
1483 return hasMoreElements();
1484 }
1485
1486 public T next() {
1487 if (Hashtable.this.modCount != expectedModCount)
1488 throw new ConcurrentModificationException();
1489 return nextElement();
1490 }
1491
1492 public void remove() {
1493 if (!iterator)
1494 throw new UnsupportedOperationException();
1495 if (lastReturned == null)
1496 throw new IllegalStateException("Hashtable Enumerator");
1497 if (modCount != expectedModCount)
1498 throw new ConcurrentModificationException();
1499
1500 synchronized(Hashtable.this) {
1501 Entry<?,?>[] tab = Hashtable.this.table;
1502 int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
1503
1504 @SuppressWarnings("unchecked")
1505 Entry<K,V> e = (Entry<K,V>)tab[index];
1506 for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1507 if (e == lastReturned) {
1508 if (prev == null)
1509 tab[index] = e.next;
1510 else
1511 prev.next = e.next;
1512 expectedModCount++;
1513 lastReturned = null;
1514 Hashtable.this.modCount++;
1515 Hashtable.this.count--;
1516 return;
1517 }
1518 }
1519 throw new ConcurrentModificationException();
1520 }
1521 }
1522 }
1523 }