001 package railo.commons.collections; 002 003 import java.io.IOException; 004 import java.util.AbstractCollection; 005 import java.util.AbstractSet; 006 import java.util.Collection; 007 import java.util.ConcurrentModificationException; 008 import java.util.Dictionary; 009 import java.util.Enumeration; 010 import java.util.Iterator; 011 import java.util.Map; 012 import java.util.NoSuchElementException; 013 import java.util.Set; 014 015 /** 016 * This class implements a hashtable, which maps keys to values. Any 017 * non-<code>null</code> object can be used as a key or as a value. <p> 018 * 019 * To successfully store and retrieve objects from a hashtable, the 020 * objects used as keys must implement the <code>hashCode</code> 021 * method and the <code>equals</code> method. <p> 022 * 023 * An instance of <code>Hashtable</code> has two parameters that affect its 024 * performance: <i>initial capacity</i> and <i>load factor</i>. The 025 * <i>capacity</i> is the number of <i>buckets</i> in the hash table, and the 026 * <i>initial capacity</i> is simply the capacity at the time the hash table 027 * is created. Note that the hash table is <i>open</i>: in the case a "hash 028 * collision", a single bucket stores multiple entries, which must be searched 029 * sequentially. The <i>load factor</i> is a measure of how full the hash 030 * table is allowed to get before its capacity is automatically increased. 031 * When the number of entries in the hashtable exceeds the product of the load 032 * factor and the current capacity, the capacity is increased by calling the 033 * <code>rehash</code> method.<p> 034 * 035 * Generally, the default load factor (.75) offers a good tradeoff between 036 * time and space costs. Higher values decrease the space overhead but 037 * increase the time cost to look up an entry (which is reflected in most 038 * <tt>Hashtable</tt> operations, including <tt>get</tt> and <tt>put</tt>).<p> 039 * 040 * The initial capacity controls a tradeoff between wasted space and the 041 * need for <code>rehash</code> operations, which are time-consuming. 042 * No <code>rehash</code> operations will <i>ever</i> occur if the initial 043 * capacity is greater than the maximum number of entries the 044 * <tt>Hashtable</tt> will contain divided by its load factor. However, 045 * setting the initial capacity too high can waste space.<p> 046 * 047 * If many entries are to be made into a <code>Hashtable</code>, 048 * creating it with a sufficiently large capacity may allow the 049 * entries to be inserted more efficiently than letting it perform 050 * automatic rehashing as needed to grow the table. <p> 051 * 052 * This example creates a hashtable of numbers. It uses the names of 053 * the numbers as keys: 054 * <p><blockquote><pre> 055 * Hashtable numbers = new Hashtable(); 056 * numbers.put("one", new Integer(1)); 057 * numbers.put("two", new Integer(2)); 058 * numbers.put("three", new Integer(3)); 059 * </pre></blockquote> 060 * <p> 061 * To retrieve a number, use the following code: 062 * <p><blockquote><pre> 063 * Integer n = (Integer)numbers.get("two"); 064 * if (n != null) { 065 * System.out.println("two = " + n); 066 * } 067 * </pre></blockquote> 068 * <p> 069 * As of the Java 2 platform v1.2, this class has been retrofitted to 070 * implement Map, so that it becomes a part of Java's collection framework. 071 * Unlike the new collection implementations, Hashtable is synchronized.<p> 072 * 073 * The Iterators returned by the iterator and listIterator methods 074 * of the Collections returned by all of Hashtable's "collection view methods" 075 * are <em>fail-fast</em>: if the Hashtable is structurally modified 076 * at any time after the Iterator is created, in any way except through the 077 * Iterator's own remove or add methods, the Iterator will throw a 078 * ConcurrentModificationException. Thus, in the face of concurrent 079 * modification, the Iterator fails quickly and cleanly, rather than risking 080 * arbitrary, non-deterministic behavior at an undetermined time in the future. 081 * The Enumerations returned by Hashtable's keys and values methods are 082 * <em>not</em> fail-fast. 083 * 084 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed 085 * as it is, generally speaking, impossible to make any hard guarantees in the 086 * presence of unsynchronized concurrent modification. Fail-fast iterators 087 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis. 088 * Therefore, it would be wrong to write a program that depended on this 089 * exception for its correctness: <i>the fail-fast behavior of iterators 090 * should be used only to detect bugs.</i> 091 */ 092 public final class HTNS extends Dictionary implements Map, Cloneable, 093 java.io.Serializable { 094 /** 095 * The hash table data. 096 */ 097 private transient Entry table[]; 098 099 /** 100 * The total number of entries in the hash table. 101 */ 102 private transient int count; 103 104 /** 105 * The table is rehashed when its size exceeds this threshold. (The 106 * value of this field is (int)(capacity * loadFactor).) 107 * 108 * @serial 109 */ 110 private int threshold; 111 112 /** 113 * The load factor for the hashtable. 114 * 115 * @serial 116 */ 117 private float loadFactor; 118 119 /** 120 * The number of times this Hashtable has been structurally modified 121 * Structural modifications are those that change the number of entries in 122 * the Hashtable or otherwise modify its internal structure (e.g., 123 * rehash). This field is used to make iterators on Collection-views of 124 * the Hashtable fail-fast. (See ConcurrentModificationException). 125 */ 126 private transient int modCount = 0; 127 128 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 129 private static final long serialVersionUID = 1421746759512286392L; 130 131 /** 132 * Constructs a new, empty hashtable with the specified initial 133 * capacity and the specified load factor. 134 * 135 * @param initialCapacity the initial capacity of the hashtable. 136 * @param loadFactor the load factor of the hashtable. 137 * @exception IllegalArgumentException if the initial capacity is less 138 * than zero, or if the load factor is nonpositive. 139 */ 140 public HTNS(int initialCapacity, float loadFactor) { 141 if (initialCapacity < 0) 142 throw new IllegalArgumentException("Illegal Capacity: "+ 143 initialCapacity); 144 if (loadFactor <= 0 || Float.isNaN(loadFactor)) 145 throw new IllegalArgumentException("Illegal Load: "+loadFactor); 146 147 if (initialCapacity==0) 148 initialCapacity = 1; 149 this.loadFactor = loadFactor; 150 table = new Entry[initialCapacity]; 151 threshold = (int)(initialCapacity * loadFactor); 152 } 153 154 /** 155 * Constructs a new, empty hashtable with the specified initial capacity 156 * and default load factor, which is <tt>0.75</tt>. 157 * 158 * @param initialCapacity the initial capacity of the hashtable. 159 * @exception IllegalArgumentException if the initial capacity is less 160 * than zero. 161 */ 162 public HTNS(int initialCapacity) { 163 this(initialCapacity, 0.75f); 164 } 165 166 /** 167 * Constructs a new, empty hashtable with a default initial capacity (11) 168 * and load factor, which is <tt>0.75</tt>. 169 */ 170 public HTNS() { 171 this(11, 0.75f); 172 } 173 174 /** 175 * Constructs a new hashtable with the same mappings as the given 176 * Map. The hashtable is created with an initial capacity sufficient to 177 * hold the mappings in the given Map and a default load factor, which is 178 * <tt>0.75</tt>. 179 * 180 * @param t the map whose mappings are to be placed in this map. 181 * @throws NullPointerException if the specified map is null. 182 * 183 */ 184 public HTNS(Map t) { 185 this(Math.max(2*t.size(), 11), 0.75f); 186 putAll(t); 187 } 188 189 /** 190 * Returns the number of keys in this hashtable. 191 * 192 * @return the number of keys in this hashtable. 193 */ 194 public int size() { 195 return count; 196 } 197 198 /** 199 * Tests if this hashtable maps no keys to values. 200 * 201 * @return <code>true</code> if this hashtable maps no keys to values; 202 * <code>false</code> otherwise. 203 */ 204 public boolean isEmpty() { 205 return count == 0; 206 } 207 208 /** 209 * Returns an enumeration of the keys in this hashtable. 210 * 211 * @return an enumeration of the keys in this hashtable. 212 * @see Enumeration 213 * @see #elements() 214 * @see #keySet() 215 * @see Map 216 */ 217 public Enumeration keys() { 218 return getEnumeration(KEYS); 219 } 220 221 /** 222 * Returns an enumeration of the values in this hashtable. 223 * Use the Enumeration methods on the returned object to fetch the elements 224 * sequentially. 225 * 226 * @return an enumeration of the values in this hashtable. 227 * @see java.util.Enumeration 228 * @see #keys() 229 * @see #values() 230 * @see Map 231 */ 232 public Enumeration elements() { 233 return getEnumeration(VALUES); 234 } 235 236 /** 237 * Tests if some key maps into the specified value in this hashtable. 238 * This operation is more expensive than the <code>containsKey</code> 239 * method.<p> 240 * 241 * Note that this method is identical in functionality to containsValue, 242 * (which is part of the Map interface in the collections framework). 243 * 244 * @param value a value to search for. 245 * @return <code>true</code> if and only if some key maps to the 246 * <code>value</code> argument in this hashtable as 247 * determined by the <tt>equals</tt> method; 248 * <code>false</code> otherwise. 249 * @exception NullPointerException if the value is <code>null</code>. 250 * @see #containsKey(Object) 251 * @see #containsValue(Object) 252 * @see Map 253 */ 254 public boolean contains(Object value) { 255 if (value == null) { 256 throw new NullPointerException(); 257 } 258 259 Entry tab[] = table; 260 for (int i = tab.length ; i-- > 0 ;) { 261 for (Entry e = tab[i] ; e != null ; e = e.next) { 262 if (e.value.equals(value)) { 263 return true; 264 } 265 } 266 } 267 return false; 268 } 269 270 /** 271 * Returns true if this Hashtable maps one or more keys to this value.<p> 272 * 273 * Note that this method is identical in functionality to contains 274 * (which predates the Map interface). 275 * 276 * @param value value whose presence in this Hashtable is to be tested. 277 * @return <tt>true</tt> if this map maps one or more keys to the 278 * specified value. 279 * @see Map 280 * 281 */ 282 public boolean containsValue(Object value) { 283 return contains(value); 284 } 285 286 /** 287 * Tests if the specified object is a key in this hashtable. 288 * 289 * @param key possible key. 290 * @return <code>true</code> if and only if the specified object 291 * is a key in this hashtable, as determined by the 292 * <tt>equals</tt> method; <code>false</code> otherwise. 293 * @see #contains(Object) 294 */ 295 public boolean containsKey(Object key) { 296 Entry tab[] = table; 297 int hash = key.hashCode(); 298 int index = (hash & 0x7FFFFFFF) % tab.length; 299 for (Entry e = tab[index] ; e != null ; e = e.next) { 300 if ((e.hash == hash) && e.key.equals(key)) { 301 return true; 302 } 303 } 304 return false; 305 } 306 307 /** 308 * Returns the value to which the specified key is mapped in this hashtable. 309 * 310 * @param key a key in the hashtable. 311 * @return the value to which the key is mapped in this hashtable; 312 * <code>null</code> if the key is not mapped to any value in 313 * this hashtable. 314 * @see #put(Object, Object) 315 */ 316 public Object get(Object key) { 317 Entry tab[] = table; 318 int hash = key.hashCode(); 319 //int index = (hash & 0x7FFFFFFF) % tab.length; 320 int index = (hash) % tab.length; 321 for (Entry e = tab[index] ; e != null ; e = e.next) { 322 if ((e.hash == hash)) { 323 return e.value; 324 } 325 } 326 return null; 327 } 328 329 /** 330 * Increases the capacity of and internally reorganizes this 331 * hashtable, in order to accommodate and access its entries more 332 * efficiently. This method is called automatically when the 333 * number of keys in the hashtable exceeds this hashtable's capacity 334 * and load factor. 335 */ 336 protected void rehash() { 337 int oldCapacity = table.length; 338 Entry oldMap[] = table; 339 340 int newCapacity = oldCapacity * 2 + 1; 341 Entry newMap[] = new Entry[newCapacity]; 342 343 modCount++; 344 threshold = (int)(newCapacity * loadFactor); 345 table = newMap; 346 347 for (int i = oldCapacity ; i-- > 0 ;) { 348 for (Entry old = oldMap[i] ; old != null ; ) { 349 Entry e = old; 350 old = old.next; 351 352 int index = (e.hash & 0x7FFFFFFF) % newCapacity; 353 e.next = newMap[index]; 354 newMap[index] = e; 355 } 356 } 357 } 358 359 /** 360 * Maps the specified <code>key</code> to the specified 361 * <code>value</code> in this hashtable. Neither the key nor the 362 * value can be <code>null</code>. <p> 363 * 364 * The value can be retrieved by calling the <code>get</code> method 365 * with a key that is equal to the original key. 366 * 367 * @param key the hashtable key. 368 * @param value the value. 369 * @return the previous value of the specified key in this hashtable, 370 * or <code>null</code> if it did not have one. 371 * @exception NullPointerException if the key or value is 372 * <code>null</code>. 373 * @see Object#equals(Object) 374 * @see #get(Object) 375 */ 376 public Object put(Object key, Object value) { 377 // Make sure the value is not null 378 if (value == null) { 379 return remove(key); 380 } 381 382 // Makes sure the key is not already in the hashtable. 383 Entry tab[] = table; 384 int hash = key.hashCode(); 385 int index = (hash & 0x7FFFFFFF) % tab.length; 386 for (Entry e = tab[index] ; e != null ; e = e.next) { 387 if ((e.hash == hash) && e.key.equals(key)) { 388 Object old = e.value; 389 e.value = value; 390 return old; 391 } 392 } 393 394 modCount++; 395 if (count >= threshold) { 396 // Rehash the table if the threshold is exceeded 397 rehash(); 398 399 tab = table; 400 index = (hash & 0x7FFFFFFF) % tab.length; 401 } 402 403 // Creates the new entry. 404 Entry e = new Entry(hash, key, value, tab[index]); 405 tab[index] = e; 406 count++; 407 return null; 408 } 409 410 /** 411 * Removes the key (and its corresponding value) from this 412 * hashtable. This method does nothing if the key is not in the hashtable. 413 * 414 * @param key the key that needs to be removed. 415 * @return the value to which the key had been mapped in this hashtable, 416 * or <code>null</code> if the key did not have a mapping. 417 */ 418 public Object remove(Object key) { 419 Entry tab[] = table; 420 int hash = key.hashCode(); 421 int index = (hash & 0x7FFFFFFF) % tab.length; 422 for (Entry e = tab[index], prev = null ; e != null ; prev = e, e = e.next) { 423 if ((e.hash == hash) && e.key.equals(key)) { 424 modCount++; 425 if (prev != null) { 426 prev.next = e.next; 427 } else { 428 tab[index] = e.next; 429 } 430 count--; 431 Object oldValue = e.value; 432 e.value = null; 433 return oldValue; 434 } 435 } 436 return null; 437 } 438 439 /** 440 * Copies all of the mappings from the specified Map to this Hashtable 441 * These mappings will replace any mappings that this Hashtable had for any 442 * of the keys currently in the specified Map. 443 * 444 * @param t Mappings to be stored in this map. 445 * @throws NullPointerException if the specified map is null. 446 * 447 */ 448 public void putAll(Map t) { 449 Iterator i = t.entrySet().iterator(); 450 while (i.hasNext()) { 451 Map.Entry e = (Map.Entry) i.next(); 452 put(e.getKey(), e.getValue()); 453 } 454 } 455 456 /** 457 * Clears this hashtable so that it contains no keys. 458 */ 459 public void clear() { 460 Entry tab[] = table; 461 modCount++; 462 for (int index = tab.length; --index >= 0; ) 463 tab[index] = null; 464 count = 0; 465 } 466 467 /** 468 * Creates a shallow copy of this hashtable. All the structure of the 469 * hashtable itself is copied, but the keys and values are not cloned. 470 * This is a relatively expensive operation. 471 * 472 * @return a clone of the hashtable. 473 */ 474 public Object clone() { 475 try { 476 HTNS t = (HTNS)super.clone(); 477 t.table = new Entry[table.length]; 478 for (int i = table.length ; i-- > 0 ; ) { 479 t.table[i] = (table[i] != null) 480 ? (Entry)table[i].clone() : null; 481 } 482 t.keySet = null; 483 t.entrySet = null; 484 t.values = null; 485 t.modCount = 0; 486 return t; 487 } catch (CloneNotSupportedException e) { 488 // this shouldn't happen, since we are Cloneable 489 throw new InternalError(); 490 } 491 } 492 493 /** 494 * Returns a string representation of this <tt>Hashtable</tt> object 495 * in the form of a set of entries, enclosed in braces and separated 496 * by the ASCII characters "<tt>, </tt>" (comma and space). Each 497 * entry is rendered as the key, an equals sign <tt>=</tt>, and the 498 * associated element, where the <tt>toString</tt> method is used to 499 * convert the key and element to strings. <p>Overrides to 500 * <tt>toString</tt> method of <tt>Object</tt>. 501 * 502 * @return a string representation of this hashtable. 503 */ 504 public String toString() { 505 int max = size() - 1; 506 StringBuffer buf = new StringBuffer(); 507 Iterator it = entrySet().iterator(); 508 509 buf.append("{"); 510 for (int i = 0; i <= max; i++) { 511 Map.Entry e = (Map.Entry) (it.next()); 512 Object key = e.getKey(); 513 Object value = e.getValue(); 514 buf.append((key == this ? "(this Map)" : key) + "=" + 515 (value == this ? "(this Map)" : value)); 516 517 if (i < max) 518 buf.append(", "); 519 } 520 buf.append("}"); 521 return buf.toString(); 522 } 523 524 525 private Enumeration getEnumeration(int type) { 526 if (count == 0) { 527 return emptyEnumerator; 528 } 529 return new Enumerator(type, false); 530 531 } 532 533 private Iterator getIterator(int type) { 534 if (count == 0) { 535 return emptyIterator; 536 } 537 return new Enumerator(type, true); 538 } 539 540 // Views 541 542 /** 543 * Each of these fields are initialized to contain an instance of the 544 * appropriate view the first time this view is requested. The views are 545 * stateless, so there's no reason to create more than one of each. 546 */ 547 private transient volatile Set keySet = null; 548 private transient volatile Set entrySet = null; 549 private transient volatile Collection values = null; 550 551 /** 552 * Returns a Set view of the keys contained in this Hashtable. The Set 553 * is backed by the Hashtable, so changes to the Hashtable are reflected 554 * in the Set, and vice-versa. The Set supports element removal 555 * (which removes the corresponding entry from the Hashtable), but not 556 * element addition. 557 * 558 * @return a set view of the keys contained in this map. 559 * 560 */ 561 public Set keySet() { 562 if (keySet == null) 563 keySet = Collections.synchronizedSet(new KeySet(), this); 564 return keySet; 565 } 566 567 private class KeySet extends AbstractSet { 568 /** 569 * @see java.util.Set#iterator() 570 */ 571 public Iterator iterator() { 572 return getIterator(KEYS); 573 } 574 /** 575 * @see java.util.Set#size() 576 */ 577 public int size() { 578 return count; 579 } 580 /** 581 * @see java.util.Set#contains(java.lang.Object) 582 */ 583 public boolean contains(Object o) { 584 return containsKey(o); 585 } 586 /** 587 * @see java.util.Set#remove(java.lang.Object) 588 */ 589 public boolean remove(Object o) { 590 return HTNS.this.remove(o) != null; 591 } 592 /** 593 * @see java.util.Set#clear() 594 */ 595 public void clear() { 596 HTNS.this.clear(); 597 } 598 } 599 600 /** 601 * Returns a Set view of the entries contained in this Hashtable. 602 * Each element in this collection is a Map.Entry. The Set is 603 * backed by the Hashtable, so changes to the Hashtable are reflected in 604 * the Set, and vice-versa. The Set supports element removal 605 * (which removes the corresponding entry from the Hashtable), 606 * but not element addition. 607 * 608 * @return a set view of the mappings contained in this map. 609 * @see Map.Entry 610 * 611 */ 612 public Set entrySet() { 613 if (entrySet==null) 614 entrySet = Collections.synchronizedSet(new EntrySet(), this); 615 return entrySet; 616 } 617 618 private class EntrySet extends AbstractSet { 619 /** 620 * @see java.util.Set#iterator() 621 */ 622 public Iterator iterator() { 623 return getIterator(ENTRIES); 624 } 625 626 /** 627 * @see java.util.Set#contains(java.lang.Object) 628 */ 629 public boolean contains(Object o) { 630 if (!(o instanceof Map.Entry)) 631 return false; 632 Map.Entry entry = (Map.Entry)o; 633 Object key = entry.getKey(); 634 Entry tab[] = table; 635 int hash = key.hashCode(); 636 int index = (hash & 0x7FFFFFFF) % tab.length; 637 638 for (Entry e = tab[index]; e != null; e = e.next) 639 if (e.hash==hash && e.equals(entry)) 640 return true; 641 return false; 642 } 643 644 /** 645 * @see java.util.Set#remove(java.lang.Object) 646 */ 647 public boolean remove(Object o) { 648 if (!(o instanceof Map.Entry)) 649 return false; 650 Map.Entry entry = (Map.Entry)o; 651 Object key = entry.getKey(); 652 Entry tab[] = table; 653 int hash = key.hashCode(); 654 int index = (hash & 0x7FFFFFFF) % tab.length; 655 656 for (Entry e = tab[index], prev = null; e != null; 657 prev = e, e = e.next) { 658 if (e.hash==hash && e.equals(entry)) { 659 modCount++; 660 if (prev != null) 661 prev.next = e.next; 662 else 663 tab[index] = e.next; 664 665 count--; 666 e.value = null; 667 return true; 668 } 669 } 670 return false; 671 } 672 673 /** 674 * @see java.util.Set#size() 675 */ 676 public int size() { 677 return count; 678 } 679 680 /** 681 * @see java.util.Set#clear() 682 */ 683 public void clear() { 684 HTNS.this.clear(); 685 } 686 } 687 688 /** 689 * Returns a Collection view of the values contained in this Hashtable. 690 * The Collection is backed by the Hashtable, so changes to the Hashtable 691 * are reflected in the Collection, and vice-versa. The Collection 692 * supports element removal (which removes the corresponding entry from 693 * the Hashtable), but not element addition. 694 * 695 * @return a collection view of the values contained in this map. 696 * 697 */ 698 public Collection values() { 699 if (values==null) 700 values = Collections.synchronizedCollection(new ValueCollection(), 701 this); 702 return values; 703 } 704 705 private class ValueCollection extends AbstractCollection { 706 /** 707 * @see java.util.AbstractCollection#iterator() 708 */ 709 public Iterator iterator() { 710 return getIterator(VALUES); 711 } 712 /** 713 * @see java.util.AbstractCollection#size() 714 */ 715 public int size() { 716 return count; 717 } 718 /** 719 * @see java.util.AbstractCollection#contains(java.lang.Object) 720 */ 721 public boolean contains(Object o) { 722 return containsValue(o); 723 } 724 /** 725 * @see java.util.AbstractCollection#clear() 726 */ 727 public void clear() { 728 HTNS.this.clear(); 729 } 730 } 731 732 // Comparison and hashing 733 734 /** 735 * Compares the specified Object with this Map for equality, 736 * as per the definition in the Map interface. 737 * 738 * @param o object to be compared for equality with this Hashtable 739 * @return true if the specified Object is equal to this Map. 740 * @see Map#equals(Object) 741 * 742 */ 743 public boolean equals(Object o) { 744 if (o == this) 745 return true; 746 747 if (!(o instanceof Map)) 748 return false; 749 Map t = (Map) o; 750 if (t.size() != size()) 751 return false; 752 753 try { 754 Iterator i = entrySet().iterator(); 755 while (i.hasNext()) { 756 Map.Entry e = (Map.Entry) i.next(); 757 Object key = e.getKey(); 758 Object value = e.getValue(); 759 if (value == null) { 760 if (!(t.get(key)==null && t.containsKey(key))) 761 return false; 762 } else { 763 if (!value.equals(t.get(key))) 764 return false; 765 } 766 } 767 } catch(ClassCastException unused) { 768 return false; 769 } catch(NullPointerException unused) { 770 return false; 771 } 772 773 return true; 774 } 775 776 /** 777 * Returns the hash code value for this Map as per the definition in the 778 * Map interface. 779 * 780 * @see Map#hashCode() 781 * 782 */ 783 public int hashCode() { 784 /* 785 * This code detects the recursion caused by computing the hash code 786 * of a self-referential hash table and prevents the stack overflow 787 * that would otherwise result. This allows certain 1.1-era 788 * applets with self-referential hash tables to work. This code 789 * abuses the loadFactor field to do double-duty as a hashCode 790 * in progress flag, so as not to worsen the space performance. 791 * A negative load factor indicates that hash code computation is 792 * in progress. 793 */ 794 int h = 0; 795 if (count == 0 || loadFactor < 0) 796 return h; // Returns zero 797 798 loadFactor = -loadFactor; // Mark hashCode computation in progress 799 Entry tab[] = table; 800 for (int i = 0; i < tab.length; i++) 801 for (Entry e = tab[i]; e != null; e = e.next) 802 h += e.key.hashCode() ^ e.value.hashCode(); 803 loadFactor = -loadFactor; // Mark hashCode computation complete 804 805 return h; 806 } 807 808 /** 809 * Save the state of the Hashtable to a stream (i.e., serialize it). 810 * @param s 811 * @throws IOException 812 * 813 * @serialData The <i>capacity</i> of the Hashtable (the length of the 814 * bucket array) is emitted (int), followed by the 815 * <i>size</i> of the Hashtable (the number of key-value 816 * mappings), followed by the key (Object) and value (Object) 817 * for each key-value mapping represented by the Hashtable 818 * The key-value mappings are emitted in no particular order. 819 */ 820 private void writeObject(java.io.ObjectOutputStream s) 821 throws IOException 822 { 823 // Write out the length, threshold, loadfactor 824 s.defaultWriteObject(); 825 826 // Write out length, count of elements and then the key/value objects 827 s.writeInt(table.length); 828 s.writeInt(count); 829 for (int index = table.length-1; index >= 0; index--) { 830 Entry entry = table[index]; 831 832 while (entry != null) { 833 s.writeObject(entry.key); 834 s.writeObject(entry.value); 835 entry = entry.next; 836 } 837 } 838 } 839 840 /** 841 * Reconstitute the Hashtable from a stream (i.e., deserialize it). 842 * @param s 843 * @throws IOException 844 * @throws ClassNotFoundException 845 */ 846 private void readObject(java.io.ObjectInputStream s) 847 throws IOException, ClassNotFoundException 848 { 849 // Read in the length, threshold, and loadfactor 850 s.defaultReadObject(); 851 852 // Read the original length of the array and number of elements 853 int origlength = s.readInt(); 854 int elements = s.readInt(); 855 856 // Compute new size with a bit of room 5% to grow but 857 // No larger than the original size. Make the length 858 // odd if it's large enough, this helps distribute the entries. 859 // Guard against the length ending up zero, that's not valid. 860 int length = (int)(elements * loadFactor) + (elements / 20) + 3; 861 if (length > elements && (length & 1) == 0) 862 length--; 863 if (origlength > 0 && length > origlength) 864 length = origlength; 865 866 table = new Entry[length]; 867 count = 0; 868 869 // Read the number of elements and then all the key/value objects 870 for (; elements > 0; elements--) { 871 Object key = s.readObject(); 872 Object value = s.readObject(); 873 put(key, value); 874 } 875 } 876 877 878 /** 879 * Hashtable collision list. 880 */ 881 private static class Entry implements Map.Entry { 882 int hash; 883 Object key; 884 Object value; 885 Entry next; 886 887 /** 888 * @param hash 889 * @param key 890 * @param value 891 * @param next 892 */ 893 protected Entry(int hash, Object key, Object value, Entry next) { 894 this.hash = hash; 895 this.key = key; 896 this.value = value; 897 this.next = next; 898 } 899 900 /** 901 * @see java.lang.Object#clone() 902 */ 903 protected Object clone() { 904 return new Entry(hash, key, value, 905 (next==null ? null : (Entry)next.clone())); 906 } 907 908 // Map.Entry Ops 909 910 /** 911 * @see java.util.Map.Entry#getKey() 912 */ 913 public Object getKey() { 914 return key; 915 } 916 917 /** 918 * @see java.util.Map.Entry#getValue() 919 */ 920 public Object getValue() { 921 return value; 922 } 923 924 /** 925 * @see java.util.Map.Entry#setValue(java.lang.Object) 926 */ 927 public Object setValue(Object value) { 928 if (value == null) 929 throw new NullPointerException(); 930 931 Object oldValue = this.value; 932 this.value = value; 933 return oldValue; 934 } 935 936 /** 937 * @see java.util.Map.Entry#equals(java.lang.Object) 938 */ 939 public boolean equals(Object o) { 940 if (!(o instanceof Map.Entry)) 941 return false; 942 Map.Entry e = (Map.Entry)o; 943 944 return (key==null ? e.getKey()==null : key.equals(e.getKey())) && 945 (value==null ? e.getValue()==null : value.equals(e.getValue())); 946 } 947 948 /** 949 * @see java.util.Map.Entry#hashCode() 950 */ 951 public int hashCode() { 952 return hash ^ (value==null ? 0 : value.hashCode()); 953 } 954 955 /** 956 * @see java.lang.Object#toString() 957 */ 958 public String toString() { 959 return key.toString()+"="+value.toString(); 960 } 961 } 962 963 // Types of Enumerations/Iterations 964 private static final int KEYS = 0; 965 private static final int VALUES = 1; 966 private static final int ENTRIES = 2; 967 968 /** 969 * A hashtable enumerator class. This class implements both the 970 * Enumeration and Iterator interfaces, but individual instances 971 * can be created with the Iterator methods disabled. This is necessary 972 * to avoid unintentionally increasing the capabilities granted a user 973 * by passing an Enumeration. 974 */ 975 private class Enumerator implements Enumeration, Iterator { 976 Entry[] table = HTNS.this.table; 977 int index = table.length; 978 Entry entry = null; 979 Entry lastReturned = null; 980 int type; 981 982 /** 983 * Indicates whether this Enumerator is serving as an Iterator 984 * or an Enumeration. (true -> Iterator). 985 */ 986 boolean iterator; 987 988 /** 989 * The modCount value that the iterator believes that the backing 990 * List should have. If this expectation is violated, the iterator 991 * has detected concurrent modification. 992 */ 993 protected int expectedModCount = modCount; 994 995 Enumerator(int type, boolean iterator) { 996 this.type = type; 997 this.iterator = iterator; 998 } 999 1000 /** 1001 * @see java.util.Enumeration#hasMoreElements() 1002 */ 1003 public boolean hasMoreElements() { 1004 Entry e = entry; 1005 int i = index; 1006 Entry t[] = table; 1007 /* Use locals for faster loop iteration */ 1008 while (e == null && i > 0) { 1009 e = t[--i]; 1010 } 1011 entry = e; 1012 index = i; 1013 return e != null; 1014 } 1015 1016 /** 1017 * @see java.util.Enumeration#nextElement() 1018 */ 1019 public Object nextElement() { 1020 Entry et = entry; 1021 int i = index; 1022 Entry t[] = table; 1023 /* Use locals for faster loop iteration */ 1024 while (et == null && i > 0) { 1025 et = t[--i]; 1026 } 1027 entry = et; 1028 index = i; 1029 if (et != null) { 1030 Entry e = lastReturned = entry; 1031 entry = e.next; 1032 return type == KEYS ? e.key : (type == VALUES ? e.value : e); 1033 } 1034 throw new NoSuchElementException("Hashtable Enumerator"); 1035 } 1036 1037 /** 1038 * @see java.util.Iterator#hasNext() 1039 */ 1040 // Iterator methods 1041 public boolean hasNext() { 1042 return hasMoreElements(); 1043 } 1044 1045 /** 1046 * @see java.util.Iterator#next() 1047 */ 1048 public Object next() { 1049 if (modCount != expectedModCount) 1050 throw new ConcurrentModificationException(); 1051 return nextElement(); 1052 } 1053 1054 /** 1055 * @see java.util.Iterator#remove() 1056 */ 1057 public void remove() { 1058 if (!iterator) 1059 throw new UnsupportedOperationException(); 1060 if (lastReturned == null) 1061 throw new IllegalStateException("Hashtable Enumerator"); 1062 if (modCount != expectedModCount) 1063 throw new ConcurrentModificationException(); 1064 1065 synchronized(HTNS.this) { 1066 Entry[] tab = HTNS.this.table; 1067 int index = (lastReturned.hash & 0x7FFFFFFF) % tab.length; 1068 1069 for (Entry e = tab[index], prev = null; e != null; 1070 prev = e, e = e.next) { 1071 if (e == lastReturned) { 1072 modCount++; 1073 expectedModCount++; 1074 if (prev == null) 1075 tab[index] = e.next; 1076 else 1077 prev.next = e.next; 1078 count--; 1079 lastReturned = null; 1080 return; 1081 } 1082 } 1083 throw new ConcurrentModificationException(); 1084 } 1085 } 1086 } 1087 1088 1089 private static EmptyEnumerator emptyEnumerator = new EmptyEnumerator(); 1090 private static EmptyIterator emptyIterator = new EmptyIterator(); 1091 1092 /** 1093 * A hashtable enumerator class for empty hash tables, specializes 1094 * the general Enumerator 1095 */ 1096 private static class EmptyEnumerator implements Enumeration { 1097 1098 EmptyEnumerator() { 1099 } 1100 1101 /** 1102 * @see java.util.Enumeration#hasMoreElements() 1103 */ 1104 public boolean hasMoreElements() { 1105 return false; 1106 } 1107 1108 /** 1109 * @see java.util.Enumeration#nextElement() 1110 */ 1111 public Object nextElement() { 1112 throw new NoSuchElementException("Hashtable Enumerator"); 1113 } 1114 } 1115 1116 1117 /** 1118 * A hashtable iterator class for empty hash tables 1119 */ 1120 private static class EmptyIterator implements Iterator { 1121 1122 EmptyIterator() { 1123 } 1124 1125 /** 1126 * @see java.util.Iterator#hasNext() 1127 */ 1128 public boolean hasNext() { 1129 return false; 1130 } 1131 1132 /** 1133 * @see java.util.Iterator#next() 1134 */ 1135 public Object next() { 1136 throw new NoSuchElementException("Hashtable Iterator"); 1137 } 1138 1139 /** 1140 * @see java.util.Iterator#remove() 1141 */ 1142 public void remove() { 1143 throw new IllegalStateException("Hashtable Iterator"); 1144 } 1145 1146 } 1147 1148 }