1 /*
2 * Copyright (c) 1994, 2017, 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.misc.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 || Float.isNaN(loadFactor))
190 throw new IllegalArgumentException("Illegal Load: "+loadFactor);
191
192 if (initialCapacity==0)
193 initialCapacity = 1;
194 this.loadFactor = loadFactor;
195 table = new Entry<?,?>[initialCapacity];
196 threshold = (int)Math.min(initialCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
197 }
198
199 /**
200 * Constructs a new, empty hashtable with the specified initial capacity
201 * and default load factor (0.75).
202 *
203 * @param initialCapacity the initial capacity of the hashtable.
204 * @exception IllegalArgumentException if the initial capacity is less
205 * than zero.
206 */
207 public Hashtable(int initialCapacity) {
208 this(initialCapacity, 0.75f);
209 }
210
211 /**
212 * Constructs a new, empty hashtable with a default initial capacity (11)
213 * and load factor (0.75).
214 */
215 public Hashtable() {
216 this(11, 0.75f);
217 }
218
219 /**
220 * Constructs a new hashtable with the same mappings as the given
221 * Map. The hashtable is created with an initial capacity sufficient to
222 * hold the mappings in the given Map and a default load factor (0.75).
223 *
224 * @param t the map whose mappings are to be placed in this map.
225 * @throws NullPointerException if the specified map is null.
226 * @since 1.2
227 */
228 public Hashtable(Map<? extends K, ? extends V> t) {
229 this(Math.max(2*t.size(), 11), 0.75f);
230 putAll(t);
231 }
232
233 /**
234 * A constructor chained from {@link Properties} keeps Hashtable fields
235 * uninitialized since they are not used.
236 *
237 * @param dummy a dummy parameter
238 */
239 Hashtable(Void dummy) {}
240
241 /**
242 * Returns the number of keys in this hashtable.
243 *
244 * @return the number of keys in this hashtable.
245 */
246 public synchronized int size() {
247 return count;
248 }
249
250 /**
251 * Tests if this hashtable maps no keys to values.
252 *
253 * @return {@code true} if this hashtable maps no keys to values;
254 * {@code false} otherwise.
255 */
256 public synchronized boolean isEmpty() {
257 return count == 0;
258 }
259
260 /**
261 * Returns an enumeration of the keys in this hashtable.
262 * Use the Enumeration methods on the returned object to fetch the keys
263 * sequentially. If the hashtable is structurally modified while enumerating
264 * over the keys then the results of enumerating are undefined.
265 *
266 * @return an enumeration of the keys in this hashtable.
267 * @see Enumeration
268 * @see #elements()
269 * @see #keySet()
270 * @see Map
271 */
272 public synchronized Enumeration<K> keys() {
273 return this.<K>getEnumeration(KEYS);
274 }
275
276 /**
277 * Returns an enumeration of the values in this hashtable.
278 * Use the Enumeration methods on the returned object to fetch the elements
279 * sequentially. If the hashtable is structurally modified while enumerating
280 * over the values then the results of enumerating are undefined.
281 *
282 * @return an enumeration of the values in this hashtable.
283 * @see java.util.Enumeration
284 * @see #keys()
285 * @see #values()
286 * @see Map
287 */
288 public synchronized Enumeration<V> elements() {
289 return this.<V>getEnumeration(VALUES);
290 }
291
292 /**
293 * Tests if some key maps into the specified value in this hashtable.
294 * This operation is more expensive than the {@link #containsKey
295 * containsKey} method.
296 *
297 * <p>Note that this method is identical in functionality to
298 * {@link #containsValue containsValue}, (which is part of the
299 * {@link Map} interface in the collections framework).
300 *
301 * @param value a value to search for
302 * @return {@code true} if and only if some key maps to the
303 * {@code value} argument in this hashtable as
304 * determined by the {@code equals} method;
305 * {@code false} otherwise.
306 * @exception NullPointerException if the value is {@code null}
307 */
308 public synchronized boolean contains(Object value) {
309 if (value == null) {
310 throw new NullPointerException();
311 }
312
313 Entry<?,?> tab[] = table;
314 for (int i = tab.length ; i-- > 0 ;) {
315 for (Entry<?,?> e = tab[i] ; e != null ; e = e.next) {
316 if (e.value.equals(value)) {
317 return true;
318 }
319 }
320 }
321 return false;
322 }
323
324 /**
325 * Returns true if this hashtable maps one or more keys to this value.
326 *
327 * <p>Note that this method is identical in functionality to {@link
328 * #contains contains} (which predates the {@link Map} interface).
329 *
330 * @param value value whose presence in this hashtable is to be tested
331 * @return {@code true} if this map maps one or more keys to the
332 * specified value
333 * @throws NullPointerException if the value is {@code null}
334 * @since 1.2
335 */
336 public boolean containsValue(Object value) {
337 return contains(value);
338 }
339
340 /**
341 * Tests if the specified object is a key in this hashtable.
342 *
343 * @param key possible key
344 * @return {@code true} if and only if the specified object
345 * is a key in this hashtable, as determined by the
346 * {@code equals} method; {@code false} otherwise.
347 * @throws NullPointerException if the key is {@code null}
348 * @see #contains(Object)
349 */
350 public synchronized boolean containsKey(Object key) {
351 Entry<?,?> tab[] = table;
352 int hash = key.hashCode();
353 int index = (hash & 0x7FFFFFFF) % tab.length;
354 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
355 if ((e.hash == hash) && e.key.equals(key)) {
356 return true;
357 }
358 }
359 return false;
360 }
361
362 /**
363 * Returns the value to which the specified key is mapped,
364 * or {@code null} if this map contains no mapping for the key.
365 *
366 * <p>More formally, if this map contains a mapping from a key
367 * {@code k} to a value {@code v} such that {@code (key.equals(k))},
368 * then this method returns {@code v}; otherwise it returns
369 * {@code null}. (There can be at most one such mapping.)
370 *
371 * @param key the key whose associated value is to be returned
372 * @return the value to which the specified key is mapped, or
373 * {@code null} if this map contains no mapping for the key
374 * @throws NullPointerException if the specified key is null
375 * @see #put(Object, Object)
376 */
377 @SuppressWarnings("unchecked")
378 public synchronized V get(Object key) {
379 Entry<?,?> tab[] = table;
380 int hash = key.hashCode();
381 int index = (hash & 0x7FFFFFFF) % tab.length;
382 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
383 if ((e.hash == hash) && e.key.equals(key)) {
384 return (V)e.value;
385 }
386 }
387 return null;
388 }
389
390 /**
391 * The maximum size of array to allocate.
392 * Some VMs reserve some header words in an array.
393 * Attempts to allocate larger arrays may result in
394 * OutOfMemoryError: Requested array size exceeds VM limit
395 */
396 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
397
398 /**
399 * Increases the capacity of and internally reorganizes this
400 * hashtable, in order to accommodate and access its entries more
401 * efficiently. This method is called automatically when the
402 * number of keys in the hashtable exceeds this hashtable's capacity
403 * and load factor.
404 */
405 @SuppressWarnings("unchecked")
406 protected void rehash() {
407 int oldCapacity = table.length;
408 Entry<?,?>[] oldMap = table;
409
410 // overflow-conscious code
411 int newCapacity = (oldCapacity << 1) + 1;
412 if (newCapacity - MAX_ARRAY_SIZE > 0) {
413 if (oldCapacity == MAX_ARRAY_SIZE)
414 // Keep running with MAX_ARRAY_SIZE buckets
415 return;
416 newCapacity = MAX_ARRAY_SIZE;
417 }
418 Entry<?,?>[] newMap = new Entry<?,?>[newCapacity];
419
420 modCount++;
421 threshold = (int)Math.min(newCapacity * loadFactor, MAX_ARRAY_SIZE + 1);
422 table = newMap;
423
424 for (int i = oldCapacity ; i-- > 0 ;) {
425 for (Entry<K,V> old = (Entry<K,V>)oldMap[i] ; old != null ; ) {
426 Entry<K,V> e = old;
427 old = old.next;
428
429 int index = (e.hash & 0x7FFFFFFF) % newCapacity;
430 e.next = (Entry<K,V>)newMap[index];
431 newMap[index] = e;
432 }
433 }
434 }
435
436 private void addEntry(int hash, K key, V value, int index) {
437 Entry<?,?> tab[] = table;
438 if (count >= threshold) {
439 // Rehash the table if the threshold is exceeded
440 rehash();
441
442 tab = table;
443 hash = key.hashCode();
444 index = (hash & 0x7FFFFFFF) % tab.length;
445 }
446
447 // Creates the new entry.
448 @SuppressWarnings("unchecked")
449 Entry<K,V> e = (Entry<K,V>) tab[index];
450 tab[index] = new Entry<>(hash, key, value, e);
451 count++;
452 modCount++;
453 }
454
455 /**
456 * Maps the specified {@code key} to the specified
457 * {@code value} in this hashtable. Neither the key nor the
458 * value can be {@code null}. <p>
459 *
460 * The value can be retrieved by calling the {@code get} method
461 * with a key that is equal to the original key.
462 *
463 * @param key the hashtable key
464 * @param value the value
465 * @return the previous value of the specified key in this hashtable,
466 * or {@code null} if it did not have one
467 * @exception NullPointerException if the key or value is
468 * {@code null}
469 * @see Object#equals(Object)
470 * @see #get(Object)
471 */
472 public synchronized V put(K key, V value) {
473 // Make sure the value is not null
474 if (value == null) {
475 throw new NullPointerException();
476 }
477
478 // Makes sure the key is not already in the hashtable.
479 Entry<?,?> tab[] = table;
480 int hash = key.hashCode();
481 int index = (hash & 0x7FFFFFFF) % tab.length;
482 @SuppressWarnings("unchecked")
483 Entry<K,V> entry = (Entry<K,V>)tab[index];
484 for(; entry != null ; entry = entry.next) {
485 if ((entry.hash == hash) && entry.key.equals(key)) {
486 V old = entry.value;
487 entry.value = value;
488 return old;
489 }
490 }
491
492 addEntry(hash, key, value, index);
493 return null;
494 }
495
496 /**
497 * Removes the key (and its corresponding value) from this
498 * hashtable. This method does nothing if the key is not in the hashtable.
499 *
500 * @param key the key that needs to be removed
501 * @return the value to which the key had been mapped in this hashtable,
502 * or {@code null} if the key did not have a mapping
503 * @throws NullPointerException if the key is {@code null}
504 */
505 public synchronized V remove(Object key) {
506 Entry<?,?> tab[] = table;
507 int hash = key.hashCode();
508 int index = (hash & 0x7FFFFFFF) % tab.length;
509 @SuppressWarnings("unchecked")
510 Entry<K,V> e = (Entry<K,V>)tab[index];
511 for(Entry<K,V> prev = null ; e != null ; prev = e, e = e.next) {
512 if ((e.hash == hash) && e.key.equals(key)) {
513 if (prev != null) {
514 prev.next = e.next;
515 } else {
516 tab[index] = e.next;
517 }
518 modCount++;
519 count--;
520 V oldValue = e.value;
521 e.value = null;
522 return oldValue;
523 }
524 }
525 return null;
526 }
527
528 /**
529 * Copies all of the mappings from the specified map to this hashtable.
530 * These mappings will replace any mappings that this hashtable had for any
531 * of the keys currently in the specified map.
532 *
533 * @param t mappings to be stored in this map
534 * @throws NullPointerException if the specified map is null
535 * @since 1.2
536 */
537 public synchronized void putAll(Map<? extends K, ? extends V> t) {
538 for (Map.Entry<? extends K, ? extends V> e : t.entrySet())
539 put(e.getKey(), e.getValue());
540 }
541
542 /**
543 * Clears this hashtable so that it contains no keys.
544 */
545 public synchronized void clear() {
546 Entry<?,?> tab[] = table;
547 for (int index = tab.length; --index >= 0; )
548 tab[index] = null;
549 modCount++;
550 count = 0;
551 }
552
553 /**
554 * Creates a shallow copy of this hashtable. All the structure of the
555 * hashtable itself is copied, but the keys and values are not cloned.
556 * This is a relatively expensive operation.
557 *
558 * @return a clone of the hashtable
559 */
560 public synchronized Object clone() {
561 Hashtable<?,?> t = cloneHashtable();
562 t.table = new Entry<?,?>[table.length];
563 for (int i = table.length ; i-- > 0 ; ) {
564 t.table[i] = (table[i] != null)
565 ? (Entry<?,?>) table[i].clone() : null;
566 }
567 t.keySet = null;
568 t.entrySet = null;
569 t.values = null;
570 t.modCount = 0;
571 return t;
572 }
573
574 /** Calls super.clone() */
575 final Hashtable<?,?> cloneHashtable() {
576 try {
577 return (Hashtable<?,?>)super.clone();
578 } catch (CloneNotSupportedException e) {
579 // this shouldn't happen, since we are Cloneable
580 throw new InternalError(e);
581 }
582 }
583
584 /**
585 * Returns a string representation of this {@code Hashtable} object
586 * in the form of a set of entries, enclosed in braces and separated
587 * by the ASCII characters "<code> , </code>" (comma and space). Each
588 * entry is rendered as the key, an equals sign {@code =}, and the
589 * associated element, where the {@code toString} method is used to
590 * convert the key and element to strings.
591 *
592 * @return a string representation of this hashtable
593 */
594 public synchronized String toString() {
595 int max = size() - 1;
596 if (max == -1)
597 return "{}";
598
599 StringBuilder sb = new StringBuilder();
600 Iterator<Map.Entry<K,V>> it = entrySet().iterator();
601
602 sb.append('{');
603 for (int i = 0; ; i++) {
604 Map.Entry<K,V> e = it.next();
605 K key = e.getKey();
606 V value = e.getValue();
607 sb.append(key == this ? "(this Map)" : key.toString());
608 sb.append('=');
609 sb.append(value == this ? "(this Map)" : value.toString());
610
611 if (i == max)
612 return sb.append('}').toString();
613 sb.append(", ");
614 }
615 }
616
617
618 private <T> Enumeration<T> getEnumeration(int type) {
619 if (count == 0) {
620 return Collections.emptyEnumeration();
621 } else {
622 return new Enumerator<>(type, false);
623 }
624 }
625
626 private <T> Iterator<T> getIterator(int type) {
627 if (count == 0) {
628 return Collections.emptyIterator();
629 } else {
630 return new Enumerator<>(type, true);
631 }
632 }
633
634 // Views
635
636 /**
637 * Each of these fields are initialized to contain an instance of the
638 * appropriate view the first time this view is requested. The views are
639 * stateless, so there's no reason to create more than one of each.
640 */
641 private transient volatile Set<K> keySet;
642 private transient volatile Set<Map.Entry<K,V>> entrySet;
643 private transient volatile Collection<V> values;
644
645 /**
646 * Returns a {@link Set} view of the keys contained in this map.
647 * The set is backed by the map, so changes to the map are
648 * reflected in the set, and vice-versa. If the map is modified
649 * while an iteration over the set is in progress (except through
650 * the iterator's own {@code remove} operation), the results of
651 * the iteration are undefined. The set supports element removal,
652 * which removes the corresponding mapping from the map, via the
653 * {@code Iterator.remove}, {@code Set.remove},
654 * {@code removeAll}, {@code retainAll}, and {@code clear}
655 * operations. It does not support the {@code add} or {@code addAll}
656 * operations.
657 *
658 * @since 1.2
659 */
660 public Set<K> keySet() {
661 if (keySet == null)
662 keySet = Collections.synchronizedSet(new KeySet(), this);
663 return keySet;
664 }
665
666 private class KeySet extends AbstractSet<K> {
667 public Iterator<K> iterator() {
668 return getIterator(KEYS);
669 }
670 public int size() {
671 return count;
672 }
673 public boolean contains(Object o) {
674 return containsKey(o);
675 }
676 public boolean remove(Object o) {
677 return Hashtable.this.remove(o) != null;
678 }
679 public void clear() {
680 Hashtable.this.clear();
681 }
682 }
683
684 /**
685 * Returns a {@link Set} view of the mappings contained in this map.
686 * The set is backed by the map, so changes to the map are
687 * reflected in the set, and vice-versa. If the map is modified
688 * while an iteration over the set is in progress (except through
689 * the iterator's own {@code remove} operation, or through the
690 * {@code setValue} operation on a map entry returned by the
691 * iterator) the results of the iteration are undefined. The set
692 * supports element removal, which removes the corresponding
693 * mapping from the map, via the {@code Iterator.remove},
694 * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
695 * {@code clear} operations. It does not support the
696 * {@code add} or {@code addAll} operations.
697 *
698 * @since 1.2
699 */
700 public Set<Map.Entry<K,V>> entrySet() {
701 if (entrySet==null)
702 entrySet = Collections.synchronizedSet(new EntrySet(), this);
703 return entrySet;
704 }
705
706 private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
707 public Iterator<Map.Entry<K,V>> iterator() {
708 return getIterator(ENTRIES);
709 }
710
711 public boolean add(Map.Entry<K,V> o) {
712 return super.add(o);
713 }
714
715 public boolean contains(Object o) {
716 if (!(o instanceof Map.Entry))
717 return false;
718 Map.Entry<?,?> entry = (Map.Entry<?,?>)o;
719 Object key = entry.getKey();
720 Entry<?,?>[] tab = table;
721 int hash = key.hashCode();
722 int index = (hash & 0x7FFFFFFF) % tab.length;
723
724 for (Entry<?,?> e = tab[index]; e != null; e = e.next)
725 if (e.hash==hash && e.equals(entry))
726 return true;
727 return false;
728 }
729
730 public boolean remove(Object o) {
731 if (!(o instanceof Map.Entry))
732 return false;
733 Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
734 Object key = entry.getKey();
735 Entry<?,?>[] tab = table;
736 int hash = key.hashCode();
737 int index = (hash & 0x7FFFFFFF) % tab.length;
738
739 @SuppressWarnings("unchecked")
740 Entry<K,V> e = (Entry<K,V>)tab[index];
741 for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
742 if (e.hash==hash && e.equals(entry)) {
743 if (prev != null)
744 prev.next = e.next;
745 else
746 tab[index] = e.next;
747
748 e.value = null; // clear for gc.
749 modCount++;
750 count--;
751 return true;
752 }
753 }
754 return false;
755 }
756
757 public int size() {
758 return count;
759 }
760
761 public void clear() {
762 Hashtable.this.clear();
763 }
764 }
765
766 /**
767 * Returns a {@link Collection} view of the values contained in this map.
768 * The collection is backed by the map, so changes to the map are
769 * reflected in the collection, and vice-versa. If the map is
770 * modified while an iteration over the collection is in progress
771 * (except through the iterator's own {@code remove} operation),
772 * the results of the iteration are undefined. The collection
773 * supports element removal, which removes the corresponding
774 * mapping from the map, via the {@code Iterator.remove},
775 * {@code Collection.remove}, {@code removeAll},
776 * {@code retainAll} and {@code clear} operations. It does not
777 * support the {@code add} or {@code addAll} operations.
778 *
779 * @since 1.2
780 */
781 public Collection<V> values() {
782 if (values==null)
783 values = Collections.synchronizedCollection(new ValueCollection(),
784 this);
785 return values;
786 }
787
788 private class ValueCollection extends AbstractCollection<V> {
789 public Iterator<V> iterator() {
790 return getIterator(VALUES);
791 }
792 public int size() {
793 return count;
794 }
795 public boolean contains(Object o) {
796 return containsValue(o);
797 }
798 public void clear() {
799 Hashtable.this.clear();
800 }
801 }
802
803 // Comparison and hashing
804
805 /**
806 * Compares the specified Object with this Map for equality,
807 * as per the definition in the Map interface.
808 *
809 * @param o object to be compared for equality with this hashtable
810 * @return true if the specified Object is equal to this Map
811 * @see Map#equals(Object)
812 * @since 1.2
813 */
814 public synchronized boolean equals(Object o) {
815 if (o == this)
816 return true;
817
818 if (!(o instanceof Map))
819 return false;
820 Map<?,?> t = (Map<?,?>) o;
821 if (t.size() != size())
822 return false;
823
824 try {
825 for (Map.Entry<K, V> e : entrySet()) {
826 K key = e.getKey();
827 V value = e.getValue();
828 if (value == null) {
829 if (!(t.get(key) == null && t.containsKey(key)))
830 return false;
831 } else {
832 if (!value.equals(t.get(key)))
833 return false;
834 }
835 }
836 } catch (ClassCastException unused) {
837 return false;
838 } catch (NullPointerException unused) {
839 return false;
840 }
841
842 return true;
843 }
844
845 /**
846 * Returns the hash code value for this Map as per the definition in the
847 * Map interface.
848 *
849 * @see Map#hashCode()
850 * @since 1.2
851 */
852 public synchronized int hashCode() {
853 /*
854 * This code detects the recursion caused by computing the hash code
855 * of a self-referential hash table and prevents the stack overflow
856 * that would otherwise result. This allows certain 1.1-era
857 * applets with self-referential hash tables to work. This code
858 * abuses the loadFactor field to do double-duty as a hashCode
859 * in progress flag, so as not to worsen the space performance.
860 * A negative load factor indicates that hash code computation is
861 * in progress.
862 */
863 int h = 0;
864 if (count == 0 || loadFactor < 0)
865 return h; // Returns zero
866
867 loadFactor = -loadFactor; // Mark hashCode computation in progress
868 Entry<?,?>[] tab = table;
869 for (Entry<?,?> entry : tab) {
870 while (entry != null) {
871 h += entry.hashCode();
872 entry = entry.next;
873 }
874 }
875
876 loadFactor = -loadFactor; // Mark hashCode computation complete
877
878 return h;
879 }
880
881 @Override
882 public synchronized V getOrDefault(Object key, V defaultValue) {
883 V result = get(key);
884 return (null == result) ? defaultValue : result;
885 }
886
887 @SuppressWarnings("unchecked")
888 @Override
889 public synchronized void forEach(BiConsumer<? super K, ? super V> action) {
890 Objects.requireNonNull(action); // explicit check required in case
891 // table is empty.
892 final int expectedModCount = modCount;
893
894 Entry<?, ?>[] tab = table;
895 for (Entry<?, ?> entry : tab) {
896 while (entry != null) {
897 action.accept((K)entry.key, (V)entry.value);
898 entry = entry.next;
899
900 if (expectedModCount != modCount) {
901 throw new ConcurrentModificationException();
902 }
903 }
904 }
905 }
906
907 @SuppressWarnings("unchecked")
908 @Override
909 public synchronized void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
910 Objects.requireNonNull(function); // explicit check required in case
911 // table is empty.
912 final int expectedModCount = modCount;
913
914 Entry<K, V>[] tab = (Entry<K, V>[])table;
915 for (Entry<K, V> entry : tab) {
916 while (entry != null) {
917 entry.value = Objects.requireNonNull(
918 function.apply(entry.key, entry.value));
919 entry = entry.next;
920
921 if (expectedModCount != modCount) {
922 throw new ConcurrentModificationException();
923 }
924 }
925 }
926 }
927
928 @Override
929 public synchronized V putIfAbsent(K key, V value) {
930 Objects.requireNonNull(value);
931
932 // Makes sure the key is not already in the hashtable.
933 Entry<?,?> tab[] = table;
934 int hash = key.hashCode();
935 int index = (hash & 0x7FFFFFFF) % tab.length;
936 @SuppressWarnings("unchecked")
937 Entry<K,V> entry = (Entry<K,V>)tab[index];
938 for (; entry != null; entry = entry.next) {
939 if ((entry.hash == hash) && entry.key.equals(key)) {
940 V old = entry.value;
941 if (old == null) {
942 entry.value = value;
943 }
944 return old;
945 }
946 }
947
948 addEntry(hash, key, value, index);
949 return null;
950 }
951
952 @Override
953 public synchronized boolean remove(Object key, Object value) {
954 Objects.requireNonNull(value);
955
956 Entry<?,?> tab[] = table;
957 int hash = key.hashCode();
958 int index = (hash & 0x7FFFFFFF) % tab.length;
959 @SuppressWarnings("unchecked")
960 Entry<K,V> e = (Entry<K,V>)tab[index];
961 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
962 if ((e.hash == hash) && e.key.equals(key) && e.value.equals(value)) {
963 if (prev != null) {
964 prev.next = e.next;
965 } else {
966 tab[index] = e.next;
967 }
968 e.value = null; // clear for gc
969 modCount++;
970 count--;
971 return true;
972 }
973 }
974 return false;
975 }
976
977 @Override
978 public synchronized boolean replace(K key, V oldValue, V newValue) {
979 Objects.requireNonNull(oldValue);
980 Objects.requireNonNull(newValue);
981 Entry<?,?> tab[] = table;
982 int hash = key.hashCode();
983 int index = (hash & 0x7FFFFFFF) % tab.length;
984 @SuppressWarnings("unchecked")
985 Entry<K,V> e = (Entry<K,V>)tab[index];
986 for (; e != null; e = e.next) {
987 if ((e.hash == hash) && e.key.equals(key)) {
988 if (e.value.equals(oldValue)) {
989 e.value = newValue;
990 return true;
991 } else {
992 return false;
993 }
994 }
995 }
996 return false;
997 }
998
999 @Override
1000 public synchronized V replace(K key, V value) {
1001 Objects.requireNonNull(value);
1002 Entry<?,?> tab[] = table;
1003 int hash = key.hashCode();
1004 int index = (hash & 0x7FFFFFFF) % tab.length;
1005 @SuppressWarnings("unchecked")
1006 Entry<K,V> e = (Entry<K,V>)tab[index];
1007 for (; e != null; e = e.next) {
1008 if ((e.hash == hash) && e.key.equals(key)) {
1009 V oldValue = e.value;
1010 e.value = value;
1011 return oldValue;
1012 }
1013 }
1014 return null;
1015 }
1016
1017 /**
1018 * {@inheritDoc}
1019 *
1020 * <p>This method will, on a best-effort basis, throw a
1021 * {@link java.util.ConcurrentModificationException} if the mapping
1022 * function modified this map during computation.
1023 *
1024 * @throws ConcurrentModificationException if it is detected that the
1025 * mapping function modified this map
1026 */
1027 @Override
1028 public synchronized V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1029 Objects.requireNonNull(mappingFunction);
1030
1031 Entry<?,?> tab[] = table;
1032 int hash = key.hashCode();
1033 int index = (hash & 0x7FFFFFFF) % tab.length;
1034 @SuppressWarnings("unchecked")
1035 Entry<K,V> e = (Entry<K,V>)tab[index];
1036 for (; e != null; e = e.next) {
1037 if (e.hash == hash && e.key.equals(key)) {
1038 // Hashtable not accept null value
1039 return e.value;
1040 }
1041 }
1042
1043 int mc = modCount;
1044 V newValue = mappingFunction.apply(key);
1045 if (mc != modCount) { throw new ConcurrentModificationException(); }
1046 if (newValue != null) {
1047 addEntry(hash, key, newValue, index);
1048 }
1049
1050 return newValue;
1051 }
1052
1053 /**
1054 * {@inheritDoc}
1055 *
1056 * <p>This method will, on a best-effort basis, throw a
1057 * {@link java.util.ConcurrentModificationException} if the remapping
1058 * function modified this map during computation.
1059 *
1060 * @throws ConcurrentModificationException if it is detected that the
1061 * remapping function modified this map
1062 */
1063 @Override
1064 public synchronized V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1065 Objects.requireNonNull(remappingFunction);
1066
1067 Entry<?,?> tab[] = table;
1068 int hash = key.hashCode();
1069 int index = (hash & 0x7FFFFFFF) % tab.length;
1070 @SuppressWarnings("unchecked")
1071 Entry<K,V> e = (Entry<K,V>)tab[index];
1072 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1073 if (e.hash == hash && e.key.equals(key)) {
1074 int mc = modCount;
1075 V newValue = remappingFunction.apply(key, e.value);
1076 if (mc != modCount) {
1077 throw new ConcurrentModificationException();
1078 }
1079 if (newValue == null) {
1080 if (prev != null) {
1081 prev.next = e.next;
1082 } else {
1083 tab[index] = e.next;
1084 }
1085 modCount = mc + 1;
1086 count--;
1087 } else {
1088 e.value = newValue;
1089 }
1090 return newValue;
1091 }
1092 }
1093 return null;
1094 }
1095 /**
1096 * {@inheritDoc}
1097 *
1098 * <p>This method will, on a best-effort basis, throw a
1099 * {@link java.util.ConcurrentModificationException} if the remapping
1100 * function modified this map during computation.
1101 *
1102 * @throws ConcurrentModificationException if it is detected that the
1103 * remapping function modified this map
1104 */
1105 @Override
1106 public synchronized V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1107 Objects.requireNonNull(remappingFunction);
1108
1109 Entry<?,?> tab[] = table;
1110 int hash = key.hashCode();
1111 int index = (hash & 0x7FFFFFFF) % tab.length;
1112 @SuppressWarnings("unchecked")
1113 Entry<K,V> e = (Entry<K,V>)tab[index];
1114 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1115 if (e.hash == hash && Objects.equals(e.key, key)) {
1116 int mc = modCount;
1117 V newValue = remappingFunction.apply(key, e.value);
1118 if (mc != modCount) {
1119 throw new ConcurrentModificationException();
1120 }
1121 if (newValue == null) {
1122 if (prev != null) {
1123 prev.next = e.next;
1124 } else {
1125 tab[index] = e.next;
1126 }
1127 modCount = mc + 1;
1128 count--;
1129 } else {
1130 e.value = newValue;
1131 }
1132 return newValue;
1133 }
1134 }
1135
1136 int mc = modCount;
1137 V newValue = remappingFunction.apply(key, null);
1138 if (mc != modCount) { throw new ConcurrentModificationException(); }
1139 if (newValue != null) {
1140 addEntry(hash, key, newValue, index);
1141 }
1142
1143 return newValue;
1144 }
1145
1146 /**
1147 * {@inheritDoc}
1148 *
1149 * <p>This method will, on a best-effort basis, throw a
1150 * {@link java.util.ConcurrentModificationException} if the remapping
1151 * function modified this map during computation.
1152 *
1153 * @throws ConcurrentModificationException if it is detected that the
1154 * remapping function modified this map
1155 */
1156 @Override
1157 public synchronized V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1158 Objects.requireNonNull(remappingFunction);
1159
1160 Entry<?,?> tab[] = table;
1161 int hash = key.hashCode();
1162 int index = (hash & 0x7FFFFFFF) % tab.length;
1163 @SuppressWarnings("unchecked")
1164 Entry<K,V> e = (Entry<K,V>)tab[index];
1165 for (Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1166 if (e.hash == hash && e.key.equals(key)) {
1167 int mc = modCount;
1168 V newValue = remappingFunction.apply(e.value, value);
1169 if (mc != modCount) {
1170 throw new ConcurrentModificationException();
1171 }
1172 if (newValue == null) {
1173 if (prev != null) {
1174 prev.next = e.next;
1175 } else {
1176 tab[index] = e.next;
1177 }
1178 modCount = mc + 1;
1179 count--;
1180 } else {
1181 e.value = newValue;
1182 }
1183 return newValue;
1184 }
1185 }
1186
1187 if (value != null) {
1188 addEntry(hash, key, value, index);
1189 }
1190
1191 return value;
1192 }
1193
1194 /**
1195 * Save the state of the Hashtable to a stream (i.e., serialize it).
1196 *
1197 * @serialData The <i>capacity</i> of the Hashtable (the length of the
1198 * bucket array) is emitted (int), followed by the
1199 * <i>size</i> of the Hashtable (the number of key-value
1200 * mappings), followed by the key (Object) and value (Object)
1201 * for each key-value mapping represented by the Hashtable
1202 * The key-value mappings are emitted in no particular order.
1203 */
1204 private void writeObject(java.io.ObjectOutputStream s)
1205 throws IOException {
1206 writeHashtable(s);
1207 }
1208
1209 /**
1210 * Perform serialization of the Hashtable to an ObjectOutputStream.
1211 * The Properties class overrides this method.
1212 */
1213 void writeHashtable(java.io.ObjectOutputStream s)
1214 throws IOException {
1215 Entry<Object, Object> entryStack = null;
1216
1217 synchronized (this) {
1218 // Write out the threshold and loadFactor
1219 s.defaultWriteObject();
1220
1221 // Write out the length and count of elements
1222 s.writeInt(table.length);
1223 s.writeInt(count);
1224
1225 // Stack copies of the entries in the table
1226 for (Entry<?, ?> entry : table) {
1227
1228 while (entry != null) {
1229 entryStack =
1230 new Entry<>(0, entry.key, entry.value, entryStack);
1231 entry = entry.next;
1232 }
1233 }
1234 }
1235
1236 // Write out the key/value objects from the stacked entries
1237 while (entryStack != null) {
1238 s.writeObject(entryStack.key);
1239 s.writeObject(entryStack.value);
1240 entryStack = entryStack.next;
1241 }
1242 }
1243
1244 /**
1245 * Called by Properties to write out a simulated threshold and loadfactor.
1246 */
1247 final void defaultWriteHashtable(java.io.ObjectOutputStream s, int length,
1248 float loadFactor) throws IOException {
1249 this.threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
1250 this.loadFactor = loadFactor;
1251 s.defaultWriteObject();
1252 }
1253
1254 /**
1255 * Reconstitute the Hashtable from a stream (i.e., deserialize it).
1256 */
1257 private void readObject(java.io.ObjectInputStream s)
1258 throws IOException, ClassNotFoundException {
1259 readHashtable(s);
1260 }
1261
1262 /**
1263 * Perform deserialization of the Hashtable from an ObjectInputStream.
1264 * The Properties class overrides this method.
1265 */
1266 void readHashtable(java.io.ObjectInputStream s)
1267 throws IOException, ClassNotFoundException {
1268 // Read in the threshold and loadFactor
1269 s.defaultReadObject();
1270
1271 // Validate loadFactor (ignore threshold - it will be re-computed)
1272 if (loadFactor <= 0 || Float.isNaN(loadFactor))
1273 throw new StreamCorruptedException("Illegal Load: " + loadFactor);
1274
1275 // Read the original length of the array and number of elements
1276 int origlength = s.readInt();
1277 int elements = s.readInt();
1278
1279 // Validate # of elements
1280 if (elements < 0)
1281 throw new StreamCorruptedException("Illegal # of Elements: " + elements);
1282
1283 // Clamp original length to be more than elements / loadFactor
1284 // (this is the invariant enforced with auto-growth)
1285 origlength = Math.max(origlength, (int)(elements / loadFactor) + 1);
1286
1287 // Compute new length with a bit of room 5% + 3 to grow but
1288 // no larger than the clamped original length. Make the length
1289 // odd if it's large enough, this helps distribute the entries.
1290 // Guard against the length ending up zero, that's not valid.
1291 int length = (int)((elements + elements / 20) / loadFactor) + 3;
1292 if (length > elements && (length & 1) == 0)
1293 length--;
1294 length = Math.min(length, origlength);
1295
1296 // Check Map.Entry[].class since it's the nearest public type to
1297 // what we're actually creating.
1298 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Map.Entry[].class, length);
1299 table = new Entry<?,?>[length];
1300 threshold = (int)Math.min(length * loadFactor, MAX_ARRAY_SIZE + 1);
1301 count = 0;
1302
1303 // Read the number of elements and then all the key/value objects
1304 for (; elements > 0; elements--) {
1305 @SuppressWarnings("unchecked")
1306 K key = (K)s.readObject();
1307 @SuppressWarnings("unchecked")
1308 V value = (V)s.readObject();
1309 // sync is eliminated for performance
1310 reconstitutionPut(table, key, value);
1311 }
1312 }
1313
1314 /**
1315 * The put method used by readObject. This is provided because put
1316 * is overridable and should not be called in readObject since the
1317 * subclass will not yet be initialized.
1318 *
1319 * <p>This differs from the regular put method in several ways. No
1320 * checking for rehashing is necessary since the number of elements
1321 * initially in the table is known. The modCount is not incremented and
1322 * there's no synchronization because we are creating a new instance.
1323 * Also, no return value is needed.
1324 */
1325 private void reconstitutionPut(Entry<?,?>[] tab, K key, V value)
1326 throws StreamCorruptedException
1327 {
1328 if (value == null) {
1329 throw new java.io.StreamCorruptedException();
1330 }
1331 // Makes sure the key is not already in the hashtable.
1332 // This should not happen in deserialized version.
1333 int hash = key.hashCode();
1334 int index = (hash & 0x7FFFFFFF) % tab.length;
1335 for (Entry<?,?> e = tab[index] ; e != null ; e = e.next) {
1336 if ((e.hash == hash) && e.key.equals(key)) {
1337 throw new java.io.StreamCorruptedException();
1338 }
1339 }
1340 // Creates the new entry.
1341 @SuppressWarnings("unchecked")
1342 Entry<K,V> e = (Entry<K,V>)tab[index];
1343 tab[index] = new Entry<>(hash, key, value, e);
1344 count++;
1345 }
1346
1347 /**
1348 * Hashtable bucket collision list entry
1349 */
1350 private static class Entry<K,V> implements Map.Entry<K,V> {
1351 final int hash;
1352 final K key;
1353 V value;
1354 Entry<K,V> next;
1355
1356 protected Entry(int hash, K key, V value, Entry<K,V> next) {
1357 this.hash = hash;
1358 this.key = key;
1359 this.value = value;
1360 this.next = next;
1361 }
1362
1363 @SuppressWarnings("unchecked")
1364 protected Object clone() {
1365 return new Entry<>(hash, key, value,
1366 (next==null ? null : (Entry<K,V>) next.clone()));
1367 }
1368
1369 // Map.Entry Ops
1370
1371 public K getKey() {
1372 return key;
1373 }
1374
1375 public V getValue() {
1376 return value;
1377 }
1378
1379 public V setValue(V value) {
1380 if (value == null)
1381 throw new NullPointerException();
1382
1383 V oldValue = this.value;
1384 this.value = value;
1385 return oldValue;
1386 }
1387
1388 public boolean equals(Object o) {
1389 if (!(o instanceof Map.Entry))
1390 return false;
1391 Map.Entry<?,?> e = (Map.Entry<?,?>)o;
1392
1393 return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
1394 (value==null ? e.getValue()==null : value.equals(e.getValue()));
1395 }
1396
1397 public int hashCode() {
1398 return hash ^ Objects.hashCode(value);
1399 }
1400
1401 public String toString() {
1402 return key.toString()+"="+value.toString();
1403 }
1404 }
1405
1406 // Types of Enumerations/Iterations
1407 private static final int KEYS = 0;
1408 private static final int VALUES = 1;
1409 private static final int ENTRIES = 2;
1410
1411 /**
1412 * A hashtable enumerator class. This class implements both the
1413 * Enumeration and Iterator interfaces, but individual instances
1414 * can be created with the Iterator methods disabled. This is necessary
1415 * to avoid unintentionally increasing the capabilities granted a user
1416 * by passing an Enumeration.
1417 */
1418 private class Enumerator<T> implements Enumeration<T>, Iterator<T> {
1419 final Entry<?,?>[] table = Hashtable.this.table;
1420 int index = table.length;
1421 Entry<?,?> entry;
1422 Entry<?,?> lastReturned;
1423 final int type;
1424
1425 /**
1426 * Indicates whether this Enumerator is serving as an Iterator
1427 * or an Enumeration. (true -> Iterator).
1428 */
1429 final boolean iterator;
1430
1431 /**
1432 * The modCount value that the iterator believes that the backing
1433 * Hashtable should have. If this expectation is violated, the iterator
1434 * has detected concurrent modification.
1435 */
1436 protected int expectedModCount = Hashtable.this.modCount;
1437
1438 Enumerator(int type, boolean iterator) {
1439 this.type = type;
1440 this.iterator = iterator;
1441 }
1442
1443 public boolean hasMoreElements() {
1444 Entry<?,?> e = entry;
1445 int i = index;
1446 Entry<?,?>[] t = table;
1447 /* Use locals for faster loop iteration */
1448 while (e == null && i > 0) {
1449 e = t[--i];
1450 }
1451 entry = e;
1452 index = i;
1453 return e != null;
1454 }
1455
1456 @SuppressWarnings("unchecked")
1457 public T nextElement() {
1458 Entry<?,?> et = entry;
1459 int i = index;
1460 Entry<?,?>[] t = table;
1461 /* Use locals for faster loop iteration */
1462 while (et == null && i > 0) {
1463 et = t[--i];
1464 }
1465 entry = et;
1466 index = i;
1467 if (et != null) {
1468 Entry<?,?> e = lastReturned = entry;
1469 entry = e.next;
1470 return type == KEYS ? (T)e.key : (type == VALUES ? (T)e.value : (T)e);
1471 }
1472 throw new NoSuchElementException("Hashtable Enumerator");
1473 }
1474
1475 // Iterator methods
1476 public boolean hasNext() {
1477 return hasMoreElements();
1478 }
1479
1480 public T next() {
1481 if (Hashtable.this.modCount != expectedModCount)
1482 throw new ConcurrentModificationException();
1483 return nextElement();
1484 }
1485
1486 public void remove() {
1487 if (!iterator)
1488 throw new UnsupportedOperationException();
1489 if (lastReturned == null)
1490 throw new IllegalStateException("Hashtable Enumerator");
1491 if (modCount != expectedModCount)
1492 throw new ConcurrentModificationException();
1493
1494 synchronized(Hashtable.this) {
1495 Entry<?,?>[] tab = Hashtable.this.table;
1496 int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length;
1497
1498 @SuppressWarnings("unchecked")
1499 Entry<K,V> e = (Entry<K,V>)tab[index];
1500 for(Entry<K,V> prev = null; e != null; prev = e, e = e.next) {
1501 if (e == lastReturned) {
1502 if (prev == null)
1503 tab[index] = e.next;
1504 else
1505 prev.next = e.next;
1506 expectedModCount++;
1507 lastReturned = null;
1508 Hashtable.this.modCount++;
1509 Hashtable.this.count--;
1510 return;
1511 }
1512 }
1513 throw new ConcurrentModificationException();
1514 }
1515 }
1516 }
1517 }