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Comparing jsr166/src/main/java/util/AbstractMap.java (file contents):
Revision 1.9 by jsr166, Sat May 14 01:52:24 2005 UTC vs.
Revision 1.26 by jsr166, Sun May 18 23:47:55 2008 UTC

# Line 1 | Line 1
1   /*
2 < * %W% %E%
2 > * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
3 > * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *
5 < * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
6 < * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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.  Sun designates this
8 > * particular file as subject to the "Classpath" exception as provided
9 > * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 > * CA 95054 USA or visit www.sun.com if you need additional information or
23 > * have any questions.
24   */
25  
26   package java.util;
# Line 29 | Line 47 | import java.util.Map.Entry;
47   * constructor, as per the recommendation in the <tt>Map</tt> interface
48   * specification.
49   *
50 < * <p>The documentation for each non-abstract methods in this class describes its
50 > * <p>The documentation for each non-abstract method in this class describes its
51   * implementation in detail.  Each of these methods may be overridden if the
52   * map being implemented admits a more efficient implementation.
53   *
54   * <p>This class is a member of the
55 < * <a href="{@docRoot}/../guide/collections/index.html">
55 > * <a href="{@docRoot}/../technotes/guides/collections/index.html">
56   * Java Collections Framework</a>.
57   *
58   * @param <K> the type of keys maintained by this map
# Line 64 | Line 82 | public abstract class AbstractMap<K,V> i
82       * <p>This implementation returns <tt>entrySet().size()</tt>.
83       */
84      public int size() {
85 <        return entrySet().size();
85 >        return entrySet().size();
86      }
87  
88      /**
# Line 73 | Line 91 | public abstract class AbstractMap<K,V> i
91       * <p>This implementation returns <tt>size() == 0</tt>.
92       */
93      public boolean isEmpty() {
94 <        return size() == 0;
94 >        return size() == 0;
95      }
96  
97      /**
# Line 85 | Line 103 | public abstract class AbstractMap<K,V> i
103       * finding such an entry, <tt>false</tt> is returned.  Note that this
104       * implementation requires linear time in the size of the map.
105       *
88     * @throws NullPointerException {@inheritDoc}
106       * @throws ClassCastException   {@inheritDoc}
107 +     * @throws NullPointerException {@inheritDoc}
108       */
109      public boolean containsValue(Object value) {
110 <        Iterator<Entry<K,V>> i = entrySet().iterator();
111 <        if (value==null) {
112 <            while (i.hasNext()) {
113 <                Entry<K,V> e = i.next();
114 <                if (e.getValue()==null)
115 <                    return true;
116 <            }
117 <        } else {
118 <            while (i.hasNext()) {
119 <                Entry<K,V> e = i.next();
120 <                if (value.equals(e.getValue()))
121 <                    return true;
122 <            }
123 <        }
124 <        return false;
110 >        Iterator<Entry<K,V>> i = entrySet().iterator();
111 >        if (value==null) {
112 >            while (i.hasNext()) {
113 >                Entry<K,V> e = i.next();
114 >                if (e.getValue()==null)
115 >                    return true;
116 >            }
117 >        } else {
118 >            while (i.hasNext()) {
119 >                Entry<K,V> e = i.next();
120 >                if (value.equals(e.getValue()))
121 >                    return true;
122 >            }
123 >        }
124 >        return false;
125      }
126  
127      /**
# Line 116 | Line 134 | public abstract class AbstractMap<K,V> i
134       * implementation requires linear time in the size of the map; many
135       * implementations will override this method.
136       *
119     * @throws NullPointerException {@inheritDoc}
137       * @throws ClassCastException   {@inheritDoc}
138 +     * @throws NullPointerException {@inheritDoc}
139       */
140      public boolean containsKey(Object key) {
141 <        Iterator<Map.Entry<K,V>> i = entrySet().iterator();
142 <        if (key==null) {
143 <            while (i.hasNext()) {
144 <                Entry<K,V> e = i.next();
145 <                if (e.getKey()==null)
146 <                    return true;
147 <            }
148 <        } else {
149 <            while (i.hasNext()) {
150 <                Entry<K,V> e = i.next();
151 <                if (key.equals(e.getKey()))
152 <                    return true;
153 <            }
154 <        }
155 <        return false;
141 >        Iterator<Map.Entry<K,V>> i = entrySet().iterator();
142 >        if (key==null) {
143 >            while (i.hasNext()) {
144 >                Entry<K,V> e = i.next();
145 >                if (e.getKey()==null)
146 >                    return true;
147 >            }
148 >        } else {
149 >            while (i.hasNext()) {
150 >                Entry<K,V> e = i.next();
151 >                if (key.equals(e.getKey()))
152 >                    return true;
153 >            }
154 >        }
155 >        return false;
156      }
157  
158      /**
# Line 147 | Line 165 | public abstract class AbstractMap<K,V> i
165       * implementation requires linear time in the size of the map; many
166       * implementations will override this method.
167       *
150     * @throws NullPointerException          {@inheritDoc}
168       * @throws ClassCastException            {@inheritDoc}
169 +     * @throws NullPointerException          {@inheritDoc}
170       */
171      public V get(Object key) {
172 <        Iterator<Entry<K,V>> i = entrySet().iterator();
173 <        if (key==null) {
174 <            while (i.hasNext()) {
175 <                Entry<K,V> e = i.next();
176 <                if (e.getKey()==null)
177 <                    return e.getValue();
178 <            }
179 <        } else {
180 <            while (i.hasNext()) {
181 <                Entry<K,V> e = i.next();
182 <                if (key.equals(e.getKey()))
183 <                    return e.getValue();
184 <            }
185 <        }
186 <        return null;
172 >        Iterator<Entry<K,V>> i = entrySet().iterator();
173 >        if (key==null) {
174 >            while (i.hasNext()) {
175 >                Entry<K,V> e = i.next();
176 >                if (e.getKey()==null)
177 >                    return e.getValue();
178 >            }
179 >        } else {
180 >            while (i.hasNext()) {
181 >                Entry<K,V> e = i.next();
182 >                if (key.equals(e.getKey()))
183 >                    return e.getValue();
184 >            }
185 >        }
186 >        return null;
187      }
188  
189  
# Line 178 | Line 196 | public abstract class AbstractMap<K,V> i
196       * <tt>UnsupportedOperationException</tt>.
197       *
198       * @throws UnsupportedOperationException {@inheritDoc}
181     * @throws NullPointerException          {@inheritDoc}
199       * @throws ClassCastException            {@inheritDoc}
200 +     * @throws NullPointerException          {@inheritDoc}
201       * @throws IllegalArgumentException      {@inheritDoc}
202       */
203      public V put(K key, V value) {
204 <        throw new UnsupportedOperationException();
204 >        throw new UnsupportedOperationException();
205      }
206  
207      /**
# Line 204 | Line 222 | public abstract class AbstractMap<K,V> i
222       * contains a mapping for the specified key.
223       *
224       * @throws UnsupportedOperationException {@inheritDoc}
207     * @throws NullPointerException          {@inheritDoc}
225       * @throws ClassCastException            {@inheritDoc}
226 +     * @throws NullPointerException          {@inheritDoc}
227       */
228      public V remove(Object key) {
229 <        Iterator<Entry<K,V>> i = entrySet().iterator();
230 <        Entry<K,V> correctEntry = null;
231 <        if (key==null) {
232 <            while (correctEntry==null && i.hasNext()) {
233 <                Entry<K,V> e = i.next();
234 <                if (e.getKey()==null)
235 <                    correctEntry = e;
236 <            }
237 <        } else {
238 <            while (correctEntry==null && i.hasNext()) {
239 <                Entry<K,V> e = i.next();
240 <                if (key.equals(e.getKey()))
241 <                    correctEntry = e;
242 <            }
243 <        }
244 <
245 <        V oldValue = null;
246 <        if (correctEntry !=null) {
247 <            oldValue = correctEntry.getValue();
248 <            i.remove();
249 <        }
250 <        return oldValue;
229 >        Iterator<Entry<K,V>> i = entrySet().iterator();
230 >        Entry<K,V> correctEntry = null;
231 >        if (key==null) {
232 >            while (correctEntry==null && i.hasNext()) {
233 >                Entry<K,V> e = i.next();
234 >                if (e.getKey()==null)
235 >                    correctEntry = e;
236 >            }
237 >        } else {
238 >            while (correctEntry==null && i.hasNext()) {
239 >                Entry<K,V> e = i.next();
240 >                if (key.equals(e.getKey()))
241 >                    correctEntry = e;
242 >            }
243 >        }
244 >
245 >        V oldValue = null;
246 >        if (correctEntry !=null) {
247 >            oldValue = correctEntry.getValue();
248 >            i.remove();
249 >        }
250 >        return oldValue;
251      }
252  
253  
# Line 247 | Line 265 | public abstract class AbstractMap<K,V> i
265       * the <tt>put</tt> operation and the specified map is nonempty.
266       *
267       * @throws UnsupportedOperationException {@inheritDoc}
250     * @throws NullPointerException          {@inheritDoc}
268       * @throws ClassCastException            {@inheritDoc}
269 +     * @throws NullPointerException          {@inheritDoc}
270       * @throws IllegalArgumentException      {@inheritDoc}
271       */
272      public void putAll(Map<? extends K, ? extends V> m) {
273 <        Iterator<? extends Entry<? extends K, ? extends V>> i = m.entrySet().iterator();
274 <        while (i.hasNext()) {
257 <            Entry<? extends K, ? extends V> e = i.next();
258 <            put(e.getKey(), e.getValue());
259 <        }
273 >        for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
274 >            put(e.getKey(), e.getValue());
275      }
276  
277      /**
# Line 271 | Line 286 | public abstract class AbstractMap<K,V> i
286       * @throws UnsupportedOperationException {@inheritDoc}
287       */
288      public void clear() {
289 <        entrySet().clear();
289 >        entrySet().clear();
290      }
291  
292  
# Line 301 | Line 316 | public abstract class AbstractMap<K,V> i
316       * method will not all return the same set.
317       */
318      public Set<K> keySet() {
319 <        if (keySet == null) {
320 <            keySet = new AbstractSet<K>() {
321 <                public Iterator<K> iterator() {
322 <                    return new Iterator<K>() {
323 <                        private Iterator<Entry<K,V>> i = entrySet().iterator();
324 <
325 <                        public boolean hasNext() {
326 <                            return i.hasNext();
327 <                        }
328 <
329 <                        public K next() {
330 <                            return i.next().getKey();
331 <                        }
332 <
333 <                        public void remove() {
334 <                            i.remove();
335 <                        }
319 >        if (keySet == null) {
320 >            keySet = new AbstractSet<K>() {
321 >                public Iterator<K> iterator() {
322 >                    return new Iterator<K>() {
323 >                        private Iterator<Entry<K,V>> i = entrySet().iterator();
324 >
325 >                        public boolean hasNext() {
326 >                            return i.hasNext();
327 >                        }
328 >
329 >                        public K next() {
330 >                            return i.next().getKey();
331 >                        }
332 >
333 >                        public void remove() {
334 >                            i.remove();
335 >                        }
336                      };
337 <                }
337 >                }
338 >
339 >                public int size() {
340 >                    return AbstractMap.this.size();
341 >                }
342 >
343 >                public boolean isEmpty() {
344 >                    return AbstractMap.this.isEmpty();
345 >                }
346  
347 <                public int size() {
348 <                    return AbstractMap.this.size();
349 <                }
350 <
351 <                public boolean contains(Object k) {
352 <                    return AbstractMap.this.containsKey(k);
353 <                }
354 <            };
355 <        }
356 <        return keySet;
347 >                public void clear() {
348 >                    AbstractMap.this.clear();
349 >                }
350 >
351 >                public boolean contains(Object k) {
352 >                    return AbstractMap.this.containsKey(k);
353 >                }
354 >            };
355 >        }
356 >        return keySet;
357      }
358  
359      /**
# Line 349 | Line 372 | public abstract class AbstractMap<K,V> i
372       * method will not all return the same collection.
373       */
374      public Collection<V> values() {
375 <        if (values == null) {
376 <            values = new AbstractCollection<V>() {
377 <                public Iterator<V> iterator() {
378 <                    return new Iterator<V>() {
379 <                        private Iterator<Entry<K,V>> i = entrySet().iterator();
380 <
381 <                        public boolean hasNext() {
382 <                            return i.hasNext();
383 <                        }
384 <
385 <                        public V next() {
386 <                            return i.next().getValue();
387 <                        }
388 <
389 <                        public void remove() {
390 <                            i.remove();
391 <                        }
375 >        if (values == null) {
376 >            values = new AbstractCollection<V>() {
377 >                public Iterator<V> iterator() {
378 >                    return new Iterator<V>() {
379 >                        private Iterator<Entry<K,V>> i = entrySet().iterator();
380 >
381 >                        public boolean hasNext() {
382 >                            return i.hasNext();
383 >                        }
384 >
385 >                        public V next() {
386 >                            return i.next().getValue();
387 >                        }
388 >
389 >                        public void remove() {
390 >                            i.remove();
391 >                        }
392                      };
393                  }
394  
395 <                public int size() {
396 <                    return AbstractMap.this.size();
397 <                }
398 <
399 <                public boolean contains(Object v) {
400 <                    return AbstractMap.this.containsValue(v);
401 <                }
402 <            };
403 <        }
404 <        return values;
395 >                public int size() {
396 >                    return AbstractMap.this.size();
397 >                }
398 >
399 >                public boolean isEmpty() {
400 >                    return AbstractMap.this.isEmpty();
401 >                }
402 >
403 >                public void clear() {
404 >                    AbstractMap.this.clear();
405 >                }
406 >
407 >                public boolean contains(Object v) {
408 >                    return AbstractMap.this.containsValue(v);
409 >                }
410 >            };
411 >        }
412 >        return values;
413      }
414  
415      public abstract Set<Entry<K,V>> entrySet();
# Line 387 | Line 418 | public abstract class AbstractMap<K,V> i
418      // Comparison and hashing
419  
420      /**
421 <     * {@inheritDoc}
421 >     * Compares the specified object with this map for equality.  Returns
422 >     * <tt>true</tt> if the given object is also a map and the two maps
423 >     * represent the same mappings.  More formally, two maps <tt>m1</tt> and
424 >     * <tt>m2</tt> represent the same mappings if
425 >     * <tt>m1.entrySet().equals(m2.entrySet())</tt>.  This ensures that the
426 >     * <tt>equals</tt> method works properly across different implementations
427 >     * of the <tt>Map</tt> interface.
428       *
429       * <p>This implementation first checks if the specified object is this map;
430       * if so it returns <tt>true</tt>.  Then, it checks if the specified
# Line 397 | Line 434 | public abstract class AbstractMap<K,V> i
434       * contains each mapping that this map contains.  If the specified map
435       * fails to contain such a mapping, <tt>false</tt> is returned.  If the
436       * iteration completes, <tt>true</tt> is returned.
437 +     *
438 +     * @param o object to be compared for equality with this map
439 +     * @return <tt>true</tt> if the specified object is equal to this map
440       */
441      public boolean equals(Object o) {
442 <        if (o == this)
443 <            return true;
442 >        if (o == this)
443 >            return true;
444  
445 <        if (!(o instanceof Map))
446 <            return false;
447 <        Map<K,V> t = (Map<K,V>) o;
448 <        if (t.size() != size())
449 <            return false;
445 >        if (!(o instanceof Map))
446 >            return false;
447 >        Map<K,V> m = (Map<K,V>) o;
448 >        if (m.size() != size())
449 >            return false;
450  
451          try {
452              Iterator<Entry<K,V>> i = entrySet().iterator();
453              while (i.hasNext()) {
454                  Entry<K,V> e = i.next();
455 <                K key = e.getKey();
455 >                K key = e.getKey();
456                  V value = e.getValue();
457                  if (value == null) {
458 <                    if (!(t.get(key)==null && t.containsKey(key)))
458 >                    if (!(m.get(key)==null && m.containsKey(key)))
459                          return false;
460                  } else {
461 <                    if (!value.equals(t.get(key)))
461 >                    if (!value.equals(m.get(key)))
462                          return false;
463                  }
464              }
# Line 428 | Line 468 | public abstract class AbstractMap<K,V> i
468              return false;
469          }
470  
471 <        return true;
471 >        return true;
472      }
473  
474      /**
475 <     * {@inheritDoc}
475 >     * Returns the hash code value for this map.  The hash code of a map is
476 >     * defined to be the sum of the hash codes of each entry in the map's
477 >     * <tt>entrySet()</tt> view.  This ensures that <tt>m1.equals(m2)</tt>
478 >     * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps
479 >     * <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of
480 >     * {@link Object#hashCode}.
481       *
482       * <p>This implementation iterates over <tt>entrySet()</tt>, calling
483 <     * <tt>hashCode()</tt> on each element (entry) in the set, and
484 <     * adding up the results.
483 >     * {@link Map.Entry#hashCode hashCode()} on each element (entry) in the
484 >     * set, and adding up the results.
485       *
486 +     * @return the hash code value for this map
487       * @see Map.Entry#hashCode()
442     * @see Object#hashCode()
488       * @see Object#equals(Object)
489       * @see Set#equals(Object)
490       */
491      public int hashCode() {
492 <        int h = 0;
493 <        Iterator<Entry<K,V>> i = entrySet().iterator();
494 <        while (i.hasNext())
495 <            h += i.next().hashCode();
496 <        return h;
492 >        int h = 0;
493 >        Iterator<Entry<K,V>> i = entrySet().iterator();
494 >        while (i.hasNext())
495 >            h += i.next().hashCode();
496 >        return h;
497      }
498  
499      /**
# Line 459 | Line 504 | public abstract class AbstractMap<K,V> i
504       * <tt>", "</tt> (comma and space).  Each key-value mapping is rendered as
505       * the key followed by an equals sign (<tt>"="</tt>) followed by the
506       * associated value.  Keys and values are converted to strings as by
507 <     * <tt>String.valueOf(Object)</tt>.<p>
507 >     * {@link String#valueOf(Object)}.
508       *
509 <     * This implementation creates an empty string buffer, appends a left
465 <     * brace, and iterates over the map's <tt>entrySet</tt> view, appending
466 <     * the string representation of each <tt>map.entry</tt> in turn.  After
467 <     * appending each entry except the last, the string <tt>", "</tt> is
468 <     * appended.  Finally a right brace is appended.  A string is obtained
469 <     * from the stringbuffer, and returned.
470 <     *
471 <     * @return a String representation of this map.
509 >     * @return a string representation of this map
510       */
511      public String toString() {
512 <        StringBuffer buf = new StringBuffer();
513 <        buf.append("{");
514 <
515 <        Iterator<Entry<K,V>> i = entrySet().iterator();
516 <        boolean hasNext = i.hasNext();
517 <        while (hasNext) {
518 <            Entry<K,V> e = i.next();
519 <            K key = e.getKey();
512 >        Iterator<Entry<K,V>> i = entrySet().iterator();
513 >        if (! i.hasNext())
514 >            return "{}";
515 >
516 >        StringBuilder sb = new StringBuilder();
517 >        sb.append('{');
518 >        for (;;) {
519 >            Entry<K,V> e = i.next();
520 >            K key = e.getKey();
521              V value = e.getValue();
522 <            if (key == this)
523 <                buf.append("(this Map)");
524 <            else
525 <                buf.append(key);
526 <            buf.append("=");
527 <            if (value == this)
489 <                buf.append("(this Map)");
490 <            else
491 <                buf.append(value);
492 <            hasNext = i.hasNext();
493 <            if (hasNext)
494 <                buf.append(", ");
522 >            sb.append(key   == this ? "(this Map)" : key);
523 >            sb.append('=');
524 >            sb.append(value == this ? "(this Map)" : value);
525 >            if (! i.hasNext())
526 >                return sb.append('}').toString();
527 >            sb.append(", ");
528          }
496
497        buf.append("}");
498        return buf.toString();
529      }
530  
531      /**
# Line 516 | Line 546 | public abstract class AbstractMap<K,V> i
546       * Test for equality, checking for nulls.
547       */
548      private static boolean eq(Object o1, Object o2) {
549 <        return (o1 == null ? o2 == null : o1.equals(o2));
549 >        return o1 == null ? o2 == null : o1.equals(o2);
550      }
551  
552      // Implementation Note: SimpleEntry and SimpleImmutableEntry
# Line 533 | Line 563 | public abstract class AbstractMap<K,V> i
563       * facilitates the process of building custom map
564       * implementations. For example, it may be convenient to return
565       * arrays of <tt>SimpleEntry</tt> instances in method
566 <     * <tt>Map.entrySet().toArray</tt>
566 >     * <tt>Map.entrySet().toArray</tt>.
567 >     *
568 >     * @since 1.6
569       */
570 <    public static class SimpleEntry<K,V> implements Entry<K,V> {
571 <        private final K key;
572 <        private V value;
570 >    public static class SimpleEntry<K,V>
571 >        implements Entry<K,V>, java.io.Serializable
572 >    {
573 >        private static final long serialVersionUID = -8499721149061103585L;
574 >
575 >        private final K key;
576 >        private V value;
577  
578          /**
579           * Creates an entry representing a mapping from the specified
# Line 546 | Line 582 | public abstract class AbstractMap<K,V> i
582           * @param key the key represented by this entry
583           * @param value the value represented by this entry
584           */
585 <        public SimpleEntry(K key, V value) {
586 <            this.key   = key;
585 >        public SimpleEntry(K key, V value) {
586 >            this.key   = key;
587              this.value = value;
588 <        }
588 >        }
589  
590          /**
591           * Creates an entry representing the same mapping as the
592           * specified entry.
593           *
594 <         * @param entry the entry to copy.
594 >         * @param entry the entry to copy
595           */
596 <        public SimpleEntry(Entry<? extends K, ? extends V> entry) {
597 <            this.key   = entry.getKey();
596 >        public SimpleEntry(Entry<? extends K, ? extends V> entry) {
597 >            this.key   = entry.getKey();
598              this.value = entry.getValue();
599 <        }
599 >        }
600 >
601 >        /**
602 >         * Returns the key corresponding to this entry.
603 >         *
604 >         * @return the key corresponding to this entry
605 >         */
606 >        public K getKey() {
607 >            return key;
608 >        }
609 >
610 >        /**
611 >         * Returns the value corresponding to this entry.
612 >         *
613 >         * @return the value corresponding to this entry
614 >         */
615 >        public V getValue() {
616 >            return value;
617 >        }
618 >
619 >        /**
620 >         * Replaces the value corresponding to this entry with the specified
621 >         * value.
622 >         *
623 >         * @param value new value to be stored in this entry
624 >         * @return the old value corresponding to the entry
625 >         */
626 >        public V setValue(V value) {
627 >            V oldValue = this.value;
628 >            this.value = value;
629 >            return oldValue;
630 >        }
631 >
632 >        /**
633 >         * Compares the specified object with this entry for equality.
634 >         * Returns {@code true} if the given object is also a map entry and
635 >         * the two entries represent the same mapping.  More formally, two
636 >         * entries {@code e1} and {@code e2} represent the same mapping
637 >         * if<pre>
638 >         *   (e1.getKey()==null ?
639 >         *    e2.getKey()==null :
640 >         *    e1.getKey().equals(e2.getKey()))
641 >         *   &amp;&amp;
642 >         *   (e1.getValue()==null ?
643 >         *    e2.getValue()==null :
644 >         *    e1.getValue().equals(e2.getValue()))</pre>
645 >         * This ensures that the {@code equals} method works properly across
646 >         * different implementations of the {@code Map.Entry} interface.
647 >         *
648 >         * @param o object to be compared for equality with this map entry
649 >         * @return {@code true} if the specified object is equal to this map
650 >         *         entry
651 >         * @see    #hashCode
652 >         */
653 >        public boolean equals(Object o) {
654 >            if (!(o instanceof Map.Entry))
655 >                return false;
656 >            Map.Entry e = (Map.Entry)o;
657 >            return eq(key, e.getKey()) && eq(value, e.getValue());
658 >        }
659  
660 <        /**
661 <         * Returns the key corresponding to this entry.
662 <         *
663 <         * @return the key corresponding to this entry
664 <         */
665 <        public K getKey() {
666 <            return key;
667 <        }
668 <
669 <        /**
670 <         * Returns the value corresponding to this entry.
671 <         *
672 <         * @return the value corresponding to this entry
673 <         */
674 <        public V getValue() {
675 <            return value;
676 <        }
582 <
583 <        /**
584 <         * Replaces the value corresponding to this entry with the specified
585 <         * value.
586 <         *
587 <         * @param value new value to be stored in this entry
588 <         * @return the old value corresponding to the entry
589 <         */
590 <        public V setValue(V value) {
591 <            V oldValue = this.value;
592 <            this.value = value;
593 <            return oldValue;
594 <        }
595 <
596 <        public boolean equals(Object o) {
597 <            if (!(o instanceof Map.Entry))
598 <                return false;
599 <            Map.Entry e = (Map.Entry)o;
600 <            return eq(key, e.getKey()) && eq(value, e.getValue());
601 <        }
602 <
603 <        public int hashCode() {
604 <            return ((key   == null)   ? 0 :   key.hashCode()) ^
605 <                   ((value == null)   ? 0 : value.hashCode());
606 <        }
660 >        /**
661 >         * Returns the hash code value for this map entry.  The hash code
662 >         * of a map entry {@code e} is defined to be: <pre>
663 >         *   (e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
664 >         *   (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
665 >         * This ensures that {@code e1.equals(e2)} implies that
666 >         * {@code e1.hashCode()==e2.hashCode()} for any two Entries
667 >         * {@code e1} and {@code e2}, as required by the general
668 >         * contract of {@link Object#hashCode}.
669 >         *
670 >         * @return the hash code value for this map entry
671 >         * @see    #equals
672 >         */
673 >        public int hashCode() {
674 >            return (key   == null ? 0 :   key.hashCode()) ^
675 >                   (value == null ? 0 : value.hashCode());
676 >        }
677  
678          /**
679           * Returns a String representation of this map entry.  This
# Line 613 | Line 683 | public abstract class AbstractMap<K,V> i
683           *
684           * @return a String representation of this map entry
685           */
686 <        public String toString() {
687 <            return key + "=" + value;
688 <        }
686 >        public String toString() {
687 >            return key + "=" + value;
688 >        }
689  
690      }
691  
692      /**
693 <     * An Entry maintaining an immutable key and value, This class
693 >     * An Entry maintaining an immutable key and value.  This class
694       * does not support method <tt>setValue</tt>.  This class may be
695       * convenient in methods that return thread-safe snapshots of
696       * key-value mappings.
697 +     *
698 +     * @since 1.6
699       */
700 <    public static class SimpleImmutableEntry<K,V> implements Entry<K,V> {
701 <        private final K key;
702 <        private final V value;
700 >    public static class SimpleImmutableEntry<K,V>
701 >        implements Entry<K,V>, java.io.Serializable
702 >    {
703 >        private static final long serialVersionUID = 7138329143949025153L;
704 >
705 >        private final K key;
706 >        private final V value;
707  
708          /**
709           * Creates an entry representing a mapping from the specified
# Line 636 | Line 712 | public abstract class AbstractMap<K,V> i
712           * @param key the key represented by this entry
713           * @param value the value represented by this entry
714           */
715 <        public SimpleImmutableEntry(K key, V value) {
716 <            this.key   = key;
715 >        public SimpleImmutableEntry(K key, V value) {
716 >            this.key   = key;
717              this.value = value;
718 <        }
718 >        }
719  
720          /**
721           * Creates an entry representing the same mapping as the
# Line 647 | Line 723 | public abstract class AbstractMap<K,V> i
723           *
724           * @param entry the entry to copy
725           */
726 <        public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) {
727 <            this.key   = entry.getKey();
726 >        public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) {
727 >            this.key   = entry.getKey();
728              this.value = entry.getValue();
729 <        }
729 >        }
730 >
731 >        /**
732 >         * Returns the key corresponding to this entry.
733 >         *
734 >         * @return the key corresponding to this entry
735 >         */
736 >        public K getKey() {
737 >            return key;
738 >        }
739  
740 <        /**
741 <         * Returns the key corresponding to this entry.
742 <         *
743 <         * @return the key corresponding to this entry
744 <         */
745 <        public K getKey() {
746 <            return key;
747 <        }
748 <
749 <        /**
750 <         * Returns the value corresponding to this entry.
751 <         *
667 <         * @return the value corresponding to this entry
668 <         */
669 <        public V getValue() {
670 <            return value;
671 <        }
672 <
673 <        /**
674 <         * Replaces the value corresponding to this entry with the specified
675 <         * value (optional operation).  This implementation simply throws
740 >        /**
741 >         * Returns the value corresponding to this entry.
742 >         *
743 >         * @return the value corresponding to this entry
744 >         */
745 >        public V getValue() {
746 >            return value;
747 >        }
748 >
749 >        /**
750 >         * Replaces the value corresponding to this entry with the specified
751 >         * value (optional operation).  This implementation simply throws
752           * <tt>UnsupportedOperationException</tt>, as this class implements
753           * an <i>immutable</i> map entry.
754 <         *
755 <         * @param value new value to be stored in this entry
756 <         * @return (Does not return)
757 <         * @throws UnsupportedOperationException always
754 >         *
755 >         * @param value new value to be stored in this entry
756 >         * @return (Does not return)
757 >         * @throws UnsupportedOperationException always
758           */
759 <        public V setValue(V value) {
759 >        public V setValue(V value) {
760              throw new UnsupportedOperationException();
761          }
762  
763 <        public boolean equals(Object o) {
764 <            if (!(o instanceof Map.Entry))
765 <                return false;
766 <            Map.Entry e = (Map.Entry)o;
767 <            return eq(key, e.getKey()) && eq(value, e.getValue());
768 <        }
769 <
770 <        public int hashCode() {
771 <            return ((key   == null)   ? 0 :   key.hashCode()) ^
772 <                   ((value == null)   ? 0 : value.hashCode());
773 <        }
763 >        /**
764 >         * Compares the specified object with this entry for equality.
765 >         * Returns {@code true} if the given object is also a map entry and
766 >         * the two entries represent the same mapping.  More formally, two
767 >         * entries {@code e1} and {@code e2} represent the same mapping
768 >         * if<pre>
769 >         *   (e1.getKey()==null ?
770 >         *    e2.getKey()==null :
771 >         *    e1.getKey().equals(e2.getKey()))
772 >         *   &amp;&amp;
773 >         *   (e1.getValue()==null ?
774 >         *    e2.getValue()==null :
775 >         *    e1.getValue().equals(e2.getValue()))</pre>
776 >         * This ensures that the {@code equals} method works properly across
777 >         * different implementations of the {@code Map.Entry} interface.
778 >         *
779 >         * @param o object to be compared for equality with this map entry
780 >         * @return {@code true} if the specified object is equal to this map
781 >         *         entry
782 >         * @see    #hashCode
783 >         */
784 >        public boolean equals(Object o) {
785 >            if (!(o instanceof Map.Entry))
786 >                return false;
787 >            Map.Entry e = (Map.Entry)o;
788 >            return eq(key, e.getKey()) && eq(value, e.getValue());
789 >        }
790 >
791 >        /**
792 >         * Returns the hash code value for this map entry.  The hash code
793 >         * of a map entry {@code e} is defined to be: <pre>
794 >         *   (e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
795 >         *   (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
796 >         * This ensures that {@code e1.equals(e2)} implies that
797 >         * {@code e1.hashCode()==e2.hashCode()} for any two Entries
798 >         * {@code e1} and {@code e2}, as required by the general
799 >         * contract of {@link Object#hashCode}.
800 >         *
801 >         * @return the hash code value for this map entry
802 >         * @see    #equals
803 >         */
804 >        public int hashCode() {
805 >            return (key   == null ? 0 :   key.hashCode()) ^
806 >                   (value == null ? 0 : value.hashCode());
807 >        }
808  
809          /**
810           * Returns a String representation of this map entry.  This
# Line 704 | Line 814 | public abstract class AbstractMap<K,V> i
814           *
815           * @return a String representation of this map entry
816           */
817 <        public String toString() {
818 <            return key + "=" + value;
819 <        }
817 >        public String toString() {
818 >            return key + "=" + value;
819 >        }
820  
821      }
822  

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