| AbstractMap.java |
1 /*
2 * %W% %E%
3 *
4 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
5 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6 */
7
8 package java.util;
9 import java.util.Map.Entry;
10
11 /**
12 * This class provides a skeletal implementation of the <tt>Map</tt>
13 * interface, to minimize the effort required to implement this interface.
14 *
15 * <p>To implement an unmodifiable map, the programmer needs only to extend this
16 * class and provide an implementation for the <tt>entrySet</tt> method, which
17 * returns a set-view of the map's mappings. Typically, the returned set
18 * will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should
19 * not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator
20 * should not support the <tt>remove</tt> method.
21 *
22 * <p>To implement a modifiable map, the programmer must additionally override
23 * this class's <tt>put</tt> method (which otherwise throws an
24 * <tt>UnsupportedOperationException</tt>), and the iterator returned by
25 * <tt>entrySet().iterator()</tt> must additionally implement its
26 * <tt>remove</tt> method.
27 *
28 * <p>The programmer should generally provide a void (no argument) and map
29 * constructor, as per the recommendation in the <tt>Map</tt> interface
30 * specification.
31 *
32 * <p>The documentation for each non-abstract method in this class describes its
33 * implementation in detail. Each of these methods may be overridden if the
34 * map being implemented admits a more efficient implementation.
35 *
36 * <p>This class is a member of the
37 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
38 * Java Collections Framework</a>.
39 *
40 * @param <K> the type of keys maintained by this map
41 * @param <V> the type of mapped values
42 *
43 * @author Josh Bloch
44 * @author Neal Gafter
45 * @version %I%, %G%
46 * @see Map
47 * @see Collection
48 * @since 1.2
49 */
50
51 public abstract class AbstractMap<K,V> implements Map<K,V> {
52 /**
53 * Sole constructor. (For invocation by subclass constructors, typically
54 * implicit.)
55 */
56 protected AbstractMap() {
57 }
58
59 // Query Operations
60
61 /**
62 * {@inheritDoc}
63 *
64 * <p>This implementation returns <tt>entrySet().size()</tt>.
65 */
66 public int size() {
67 return entrySet().size();
68 }
69
70 /**
71 * {@inheritDoc}
72 *
73 * <p>This implementation returns <tt>size() == 0</tt>.
74 */
75 public boolean isEmpty() {
76 return size() == 0;
77 }
78
79 /**
80 * {@inheritDoc}
81 *
82 * <p>This implementation iterates over <tt>entrySet()</tt> searching
83 * for an entry with the specified value. If such an entry is found,
84 * <tt>true</tt> is returned. If the iteration terminates without
85 * finding such an entry, <tt>false</tt> is returned. Note that this
86 * implementation requires linear time in the size of the map.
87 *
88 * @throws ClassCastException {@inheritDoc}
89 * @throws NullPointerException {@inheritDoc}
90 */
91 public boolean containsValue(Object value) {
92 Iterator<Entry<K,V>> i = entrySet().iterator();
93 if (value==null) {
94 while (i.hasNext()) {
95 Entry<K,V> e = i.next();
96 if (e.getValue()==null)
97 return true;
98 }
99 } else {
100 while (i.hasNext()) {
101 Entry<K,V> e = i.next();
102 if (value.equals(e.getValue()))
103 return true;
104 }
105 }
106 return false;
107 }
108
109 /**
110 * {@inheritDoc}
111 *
112 * <p>This implementation iterates over <tt>entrySet()</tt> searching
113 * for an entry with the specified key. If such an entry is found,
114 * <tt>true</tt> is returned. If the iteration terminates without
115 * finding such an entry, <tt>false</tt> is returned. Note that this
116 * implementation requires linear time in the size of the map; many
117 * implementations will override this method.
118 *
119 * @throws ClassCastException {@inheritDoc}
120 * @throws NullPointerException {@inheritDoc}
121 */
122 public boolean containsKey(Object key) {
123 Iterator<Map.Entry<K,V>> i = entrySet().iterator();
124 if (key==null) {
125 while (i.hasNext()) {
126 Entry<K,V> e = i.next();
127 if (e.getKey()==null)
128 return true;
129 }
130 } else {
131 while (i.hasNext()) {
132 Entry<K,V> e = i.next();
133 if (key.equals(e.getKey()))
134 return true;
135 }
136 }
137 return false;
138 }
139
140 /**
141 * {@inheritDoc}
142 *
143 * <p>This implementation iterates over <tt>entrySet()</tt> searching
144 * for an entry with the specified key. If such an entry is found,
145 * the entry's value is returned. If the iteration terminates without
146 * finding such an entry, <tt>null</tt> is returned. Note that this
147 * implementation requires linear time in the size of the map; many
148 * implementations will override this method.
149 *
150 * @throws ClassCastException {@inheritDoc}
151 * @throws NullPointerException {@inheritDoc}
152 */
153 public V get(Object key) {
154 Iterator<Entry<K,V>> i = entrySet().iterator();
155 if (key==null) {
156 while (i.hasNext()) {
157 Entry<K,V> e = i.next();
158 if (e.getKey()==null)
159 return e.getValue();
160 }
161 } else {
162 while (i.hasNext()) {
163 Entry<K,V> e = i.next();
164 if (key.equals(e.getKey()))
165 return e.getValue();
166 }
167 }
168 return null;
169 }
170
171
172 // Modification Operations
173
174 /**
175 * {@inheritDoc}
176 *
177 * <p>This implementation always throws an
178 * <tt>UnsupportedOperationException</tt>.
179 *
180 * @throws UnsupportedOperationException {@inheritDoc}
181 * @throws ClassCastException {@inheritDoc}
182 * @throws NullPointerException {@inheritDoc}
183 * @throws IllegalArgumentException {@inheritDoc}
184 */
185 public V put(K key, V value) {
186 throw new UnsupportedOperationException();
187 }
188
189 /**
190 * {@inheritDoc}
191 *
192 * <p>This implementation iterates over <tt>entrySet()</tt> searching for an
193 * entry with the specified key. If such an entry is found, its value is
194 * obtained with its <tt>getValue</tt> operation, the entry is removed
195 * from the collection (and the backing map) with the iterator's
196 * <tt>remove</tt> operation, and the saved value is returned. If the
197 * iteration terminates without finding such an entry, <tt>null</tt> is
198 * returned. Note that this implementation requires linear time in the
199 * size of the map; many implementations will override this method.
200 *
201 * <p>Note that this implementation throws an
202 * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt>
203 * iterator does not support the <tt>remove</tt> method and this map
204 * contains a mapping for the specified key.
205 *
206 * @throws UnsupportedOperationException {@inheritDoc}
207 * @throws ClassCastException {@inheritDoc}
208 * @throws NullPointerException {@inheritDoc}
209 */
210 public V remove(Object key) {
211 Iterator<Entry<K,V>> i = entrySet().iterator();
212 Entry<K,V> correctEntry = null;
213 if (key==null) {
214 while (correctEntry==null && i.hasNext()) {
215 Entry<K,V> e = i.next();
216 if (e.getKey()==null)
217 correctEntry = e;
218 }
219 } else {
220 while (correctEntry==null && i.hasNext()) {
221 Entry<K,V> e = i.next();
222 if (key.equals(e.getKey()))
223 correctEntry = e;
224 }
225 }
226
227 V oldValue = null;
228 if (correctEntry !=null) {
229 oldValue = correctEntry.getValue();
230 i.remove();
231 }
232 return oldValue;
233 }
234
235
236 // Bulk Operations
237
238 /**
239 * {@inheritDoc}
240 *
241 * <p>This implementation iterates over the specified map's
242 * <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt>
243 * operation once for each entry returned by the iteration.
244 *
245 * <p>Note that this implementation throws an
246 * <tt>UnsupportedOperationException</tt> if this map does not support
247 * the <tt>put</tt> operation and the specified map is nonempty.
248 *
249 * @throws UnsupportedOperationException {@inheritDoc}
250 * @throws ClassCastException {@inheritDoc}
251 * @throws NullPointerException {@inheritDoc}
252 * @throws IllegalArgumentException {@inheritDoc}
253 */
254 public void putAll(Map<? extends K, ? extends V> m) {
255 for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
256 put(e.getKey(), e.getValue());
257 }
258
259 /**
260 * {@inheritDoc}
261 *
262 * <p>This implementation calls <tt>entrySet().clear()</tt>.
263 *
264 * <p>Note that this implementation throws an
265 * <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt>
266 * does not support the <tt>clear</tt> operation.
267 *
268 * @throws UnsupportedOperationException {@inheritDoc}
269 */
270 public void clear() {
271 entrySet().clear();
272 }
273
274
275 // Views
276
277 /**
278 * Each of these fields are initialized to contain an instance of the
279 * appropriate view the first time this view is requested. The views are
280 * stateless, so there's no reason to create more than one of each.
281 */
282 transient volatile Set<K> keySet = null;
283 transient volatile Collection<V> values = null;
284
285 /**
286 * {@inheritDoc}
287 *
288 * <p>This implementation returns a set that subclasses {@link AbstractSet}.
289 * The subclass's iterator method returns a "wrapper object" over this
290 * map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method
291 * delegates to this map's <tt>size</tt> method and the
292 * <tt>contains</tt> method delegates to this map's
293 * <tt>containsKey</tt> method.
294 *
295 * <p>The set is created the first time this method is called,
296 * and returned in response to all subsequent calls. No synchronization
297 * is performed, so there is a slight chance that multiple calls to this
298 * method will not all return the same set.
299 */
300 public Set<K> keySet() {
301 if (keySet == null) {
302 keySet = new AbstractSet<K>() {
303 public Iterator<K> iterator() {
304 return new Iterator<K>() {
305 private Iterator<Entry<K,V>> i = entrySet().iterator();
306
307 public boolean hasNext() {
308 return i.hasNext();
309 }
310
311 public K next() {
312 return i.next().getKey();
313 }
314
315 public void remove() {
316 i.remove();
317 }
318 };
319 }
320
321 public int size() {
322 return AbstractMap.this.size();
323 }
324
325 public boolean contains(Object k) {
326 return AbstractMap.this.containsKey(k);
327 }
328 };
329 }
330 return keySet;
331 }
332
333 /**
334 * {@inheritDoc}
335 *
336 * <p>This implementation returns a collection that subclasses {@link
337 * AbstractCollection}. The subclass's iterator method returns a
338 * "wrapper object" over this map's <tt>entrySet()</tt> iterator.
339 * The <tt>size</tt> method delegates to this map's <tt>size</tt>
340 * method and the <tt>contains</tt> method delegates to this map's
341 * <tt>containsValue</tt> method.
342 *
343 * <p>The collection is created the first time this method is called, and
344 * returned in response to all subsequent calls. No synchronization is
345 * performed, so there is a slight chance that multiple calls to this
346 * method will not all return the same collection.
347 */
348 public Collection<V> values() {
349 if (values == null) {
350 values = new AbstractCollection<V>() {
351 public Iterator<V> iterator() {
352 return new Iterator<V>() {
353 private Iterator<Entry<K,V>> i = entrySet().iterator();
354
355 public boolean hasNext() {
356 return i.hasNext();
357 }
358
359 public V next() {
360 return i.next().getValue();
361 }
362
363 public void remove() {
364 i.remove();
365 }
366 };
367 }
368
369 public int size() {
370 return AbstractMap.this.size();
371 }
372
373 public boolean contains(Object v) {
374 return AbstractMap.this.containsValue(v);
375 }
376 };
377 }
378 return values;
379 }
380
381 public abstract Set<Entry<K,V>> entrySet();
382
383
384 // Comparison and hashing
385
386 /**
387 * Compares the specified object with this map for equality. Returns
388 * <tt>true</tt> if the given object is also a map and the two maps
389 * represent the same mappings. More formally, two maps <tt>m1</tt> and
390 * <tt>m2</tt> represent the same mappings if
391 * <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the
392 * <tt>equals</tt> method works properly across different implementations
393 * of the <tt>Map</tt> interface.
394 *
395 * <p>This implementation first checks if the specified object is this map;
396 * if so it returns <tt>true</tt>. Then, it checks if the specified
397 * object is a map whose size is identical to the size of this map; if
398 * not, it returns <tt>false</tt>. If so, it iterates over this map's
399 * <tt>entrySet</tt> collection, and checks that the specified map
400 * contains each mapping that this map contains. If the specified map
401 * fails to contain such a mapping, <tt>false</tt> is returned. If the
402 * iteration completes, <tt>true</tt> is returned.
403 *
404 * @param o object to be compared for equality with this map
405 * @return <tt>true</tt> if the specified object is equal to this map
406 */
407 public boolean equals(Object o) {
408 if (o == this)
409 return true;
410
411 if (!(o instanceof Map))
412 return false;
413 Map<K,V> m = (Map<K,V>) o;
414 if (m.size() != size())
415 return false;
416
417 try {
418 Iterator<Entry<K,V>> i = entrySet().iterator();
419 while (i.hasNext()) {
420 Entry<K,V> e = i.next();
421 K key = e.getKey();
422 V value = e.getValue();
423 if (value == null) {
424 if (!(m.get(key)==null && m.containsKey(key)))
425 return false;
426 } else {
427 if (!value.equals(m.get(key)))
428 return false;
429 }
430 }
431 } catch (ClassCastException unused) {
432 return false;
433 } catch (NullPointerException unused) {
434 return false;
435 }
436
437 return true;
438 }
439
440 /**
441 * Returns the hash code value for this map. The hash code of a map is
442 * defined to be the sum of the hash codes of each entry in the map's
443 * <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt>
444 * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps
445 * <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of
446 * {@link Object#hashCode}.
447 *
448 * <p>This implementation iterates over <tt>entrySet()</tt>, calling
449 * {@link Map.Entry#hashCode hashCode()} on each element (entry) in the
450 * set, and adding up the results.
451 *
452 * @return the hash code value for this map
453 * @see Map.Entry#hashCode()
454 * @see Object#equals(Object)
455 * @see Set#equals(Object)
456 */
457 public int hashCode() {
458 int h = 0;
459 Iterator<Entry<K,V>> i = entrySet().iterator();
460 while (i.hasNext())
461 h += i.next().hashCode();
462 return h;
463 }
464
465 /**
466 * Returns a string representation of this map. The string representation
467 * consists of a list of key-value mappings in the order returned by the
468 * map's <tt>entrySet</tt> view's iterator, enclosed in braces
469 * (<tt>"{}"</tt>). Adjacent mappings are separated by the characters
470 * <tt>", "</tt> (comma and space). Each key-value mapping is rendered as
471 * the key followed by an equals sign (<tt>"="</tt>) followed by the
472 * associated value. Keys and values are converted to strings as by
473 * {@link String#valueOf(Object)}.
474 *
475 * @return a string representation of this map
476 */
477 public String toString() {
478 Iterator<Entry<K,V>> i = entrySet().iterator();
479 if (! i.hasNext())
480 return "{}";
481
482 StringBuilder sb = new StringBuilder();
483 sb.append('{');
484 for (;;) {
485 Entry<K,V> e = i.next();
486 K key = e.getKey();
487 V value = e.getValue();
488 sb.append(key == this ? "(this Map)" : key);
489 sb.append('=');
490 sb.append(value == this ? "(this Map)" : value);
491 if (! i.hasNext())
492 return sb.append('}').toString();
493 sb.append(", ");
494 }
495 }
496
497 /**
498 * Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys
499 * and values themselves are not cloned.
500 *
501 * @return a shallow copy of this map
502 */
503 protected Object clone() throws CloneNotSupportedException {
504 AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone();
505 result.keySet = null;
506 result.values = null;
507 return result;
508 }
509
510 /**
511 * Utility method for SimpleEntry and SimpleImmutableEntry.
512 * Test for equality, checking for nulls.
513 */
514 private static boolean eq(Object o1, Object o2) {
515 return o1 == null ? o2 == null : o1.equals(o2);
516 }
517
518 // Implementation Note: SimpleEntry and SimpleImmutableEntry
519 // are distinct unrelated classes, even though they share
520 // some code. Since you can't add or subtract final-ness
521 // of a field in a subclass, they can't share representations,
522 // and the amount of duplicated code is too small to warrant
523 // exposing a common abstract class.
524
525
526 /**
527 * An Entry maintaining a key and a value. The value may be
528 * changed using the <tt>setValue</tt> method. This class
529 * facilitates the process of building custom map
530 * implementations. For example, it may be convenient to return
531 * arrays of <tt>SimpleEntry</tt> instances in method
532 * <tt>Map.entrySet().toArray</tt>.
533 *
534 * @since 1.6
535 */
536 public static class SimpleEntry<K,V>
537 implements Entry<K,V>, java.io.Serializable
538 {
539 private static final long serialVersionUID = -8499721149061103585L;
540
541 private final K key;
542 private V value;
543
544 /**
545 * Creates an entry representing a mapping from the specified
546 * key to the specified value.
547 *
548 * @param key the key represented by this entry
549 * @param value the value represented by this entry
550 */
551 public SimpleEntry(K key, V value) {
552 this.key = key;
553 this.value = value;
554 }
555
556 /**
557 * Creates an entry representing the same mapping as the
558 * specified entry.
559 *
560 * @param entry the entry to copy
561 */
562 public SimpleEntry(Entry<? extends K, ? extends V> entry) {
563 this.key = entry.getKey();
564 this.value = entry.getValue();
565 }
566
567 /**
568 * Returns the key corresponding to this entry.
569 *
570 * @return the key corresponding to this entry
571 */
572 public K getKey() {
573 return key;
574 }
575
576 /**
577 * Returns the value corresponding to this entry.
578 *
579 * @return the value corresponding to this entry
580 */
581 public V getValue() {
582 return value;
583 }
584
585 /**
586 * Replaces the value corresponding to this entry with the specified
587 * value.
588 *
589 * @param value new value to be stored in this entry
590 * @return the old value corresponding to the entry
591 */
592 public V setValue(V value) {
593 V oldValue = this.value;
594 this.value = value;
595 return oldValue;
596 }
597
598 /**
599 * Compares the specified object with this entry for equality.
600 * Returns {@code true} if the given object is also a map entry and
601 * the two entries represent the same mapping. More formally, two
602 * entries {@code e1} and {@code e2} represent the same mapping
603 * if<pre>
604 * (e1.getKey()==null ?
605 * e2.getKey()==null :
606 * e1.getKey().equals(e2.getKey()))
607 * &&
608 * (e1.getValue()==null ?
609 * e2.getValue()==null :
610 * e1.getValue().equals(e2.getValue()))</pre>
611 * This ensures that the {@code equals} method works properly across
612 * different implementations of the {@code Map.Entry} interface.
613 *
614 * @param o object to be compared for equality with this map entry
615 * @return {@code true} if the specified object is equal to this map
616 * entry
617 * @see #hashCode
618 */
619 public boolean equals(Object o) {
620 if (!(o instanceof Map.Entry))
621 return false;
622 Map.Entry e = (Map.Entry)o;
623 return eq(key, e.getKey()) && eq(value, e.getValue());
624 }
625
626 /**
627 * Returns the hash code value for this map entry. The hash code
628 * of a map entry {@code e} is defined to be: <pre>
629 * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
630 * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
631 * This ensures that {@code e1.equals(e2)} implies that
632 * {@code e1.hashCode()==e2.hashCode()} for any two Entries
633 * {@code e1} and {@code e2}, as required by the general
634 * contract of {@link Object#hashCode}.
635 *
636 * @return the hash code value for this map entry
637 * @see #equals
638 */
639 public int hashCode() {
640 return (key == null ? 0 : key.hashCode()) ^
641 (value == null ? 0 : value.hashCode());
642 }
643
644 /**
645 * Returns a String representation of this map entry. This
646 * implementation returns the string representation of this
647 * entry's key followed by the equals character ("<tt>=</tt>")
648 * followed by the string representation of this entry's value.
649 *
650 * @return a String representation of this map entry
651 */
652 public String toString() {
653 return key + "=" + value;
654 }
655
656 }
657
658 /**
659 * An Entry maintaining an immutable key and value. This class
660 * does not support method <tt>setValue</tt>. This class may be
661 * convenient in methods that return thread-safe snapshots of
662 * key-value mappings.
663 *
664 * @since 1.6
665 */
666 public static class SimpleImmutableEntry<K,V>
667 implements Entry<K,V>, java.io.Serializable
668 {
669 private static final long serialVersionUID = 7138329143949025153L;
670
671 private final K key;
672 private final V value;
673
674 /**
675 * Creates an entry representing a mapping from the specified
676 * key to the specified value.
677 *
678 * @param key the key represented by this entry
679 * @param value the value represented by this entry
680 */
681 public SimpleImmutableEntry(K key, V value) {
682 this.key = key;
683 this.value = value;
684 }
685
686 /**
687 * Creates an entry representing the same mapping as the
688 * specified entry.
689 *
690 * @param entry the entry to copy
691 */
692 public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) {
693 this.key = entry.getKey();
694 this.value = entry.getValue();
695 }
696
697 /**
698 * Returns the key corresponding to this entry.
699 *
700 * @return the key corresponding to this entry
701 */
702 public K getKey() {
703 return key;
704 }
705
706 /**
707 * Returns the value corresponding to this entry.
708 *
709 * @return the value corresponding to this entry
710 */
711 public V getValue() {
712 return value;
713 }
714
715 /**
716 * Replaces the value corresponding to this entry with the specified
717 * value (optional operation). This implementation simply throws
718 * <tt>UnsupportedOperationException</tt>, as this class implements
719 * an <i>immutable</i> map entry.
720 *
721 * @param value new value to be stored in this entry
722 * @return (Does not return)
723 * @throws UnsupportedOperationException always
724 */
725 public V setValue(V value) {
726 throw new UnsupportedOperationException();
727 }
728
729 /**
730 * Compares the specified object with this entry for equality.
731 * Returns {@code true} if the given object is also a map entry and
732 * the two entries represent the same mapping. More formally, two
733 * entries {@code e1} and {@code e2} represent the same mapping
734 * if<pre>
735 * (e1.getKey()==null ?
736 * e2.getKey()==null :
737 * e1.getKey().equals(e2.getKey()))
738 * &&
739 * (e1.getValue()==null ?
740 * e2.getValue()==null :
741 * e1.getValue().equals(e2.getValue()))</pre>
742 * This ensures that the {@code equals} method works properly across
743 * different implementations of the {@code Map.Entry} interface.
744 *
745 * @param o object to be compared for equality with this map entry
746 * @return {@code true} if the specified object is equal to this map
747 * entry
748 * @see #hashCode
749 */
750 public boolean equals(Object o) {
751 if (!(o instanceof Map.Entry))
752 return false;
753 Map.Entry e = (Map.Entry)o;
754 return eq(key, e.getKey()) && eq(value, e.getValue());
755 }
756
757 /**
758 * Returns the hash code value for this map entry. The hash code
759 * of a map entry {@code e} is defined to be: <pre>
760 * (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
761 * (e.getValue()==null ? 0 : e.getValue().hashCode())</pre>
762 * This ensures that {@code e1.equals(e2)} implies that
763 * {@code e1.hashCode()==e2.hashCode()} for any two Entries
764 * {@code e1} and {@code e2}, as required by the general
765 * contract of {@link Object#hashCode}.
766 *
767 * @return the hash code value for this map entry
768 * @see #equals
769 */
770 public int hashCode() {
771 return (key == null ? 0 : key.hashCode()) ^
772 (value == null ? 0 : value.hashCode());
773 }
774
775 /**
776 * Returns a String representation of this map entry. This
777 * implementation returns the string representation of this
778 * entry's key followed by the equals character ("<tt>=</tt>")
779 * followed by the string representation of this entry's value.
780 *
781 * @return a String representation of this map entry
782 */
783 public String toString() {
784 return key + "=" + value;
785 }
786
787 }
788
789 }
790