1 |
/* |
2 |
* %W% %E% |
3 |
* |
4 |
* Copyright 2005 Sun Microsystems, Inc. All rights reserved. |
5 |
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. |
6 |
*/ |
7 |
|
8 |
package java.util; |
9 |
import java.util.*; // for javadoc (till 6280605 is fixed) |
10 |
import java.util.Map.Entry; |
11 |
|
12 |
/** |
13 |
* This class provides a skeletal implementation of the <tt>Map</tt> |
14 |
* interface, to minimize the effort required to implement this interface. |
15 |
* |
16 |
* <p>To implement an unmodifiable map, the programmer needs only to extend this |
17 |
* class and provide an implementation for the <tt>entrySet</tt> method, which |
18 |
* returns a set-view of the map's mappings. Typically, the returned set |
19 |
* will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should |
20 |
* not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator |
21 |
* should not support the <tt>remove</tt> method. |
22 |
* |
23 |
* <p>To implement a modifiable map, the programmer must additionally override |
24 |
* this class's <tt>put</tt> method (which otherwise throws an |
25 |
* <tt>UnsupportedOperationException</tt>), and the iterator returned by |
26 |
* <tt>entrySet().iterator()</tt> must additionally implement its |
27 |
* <tt>remove</tt> method. |
28 |
* |
29 |
* <p>The programmer should generally provide a void (no argument) and map |
30 |
* constructor, as per the recommendation in the <tt>Map</tt> interface |
31 |
* specification. |
32 |
* |
33 |
* <p>The documentation for each non-abstract methods in this class describes its |
34 |
* implementation in detail. Each of these methods may be overridden if the |
35 |
* map being implemented admits a more efficient implementation. |
36 |
* |
37 |
* <p>This class is a member of the |
38 |
* <a href="{@docRoot}/../guide/collections/index.html"> |
39 |
* Java Collections Framework</a>. |
40 |
* |
41 |
* @param <K> the type of keys maintained by this map |
42 |
* @param <V> the type of mapped values |
43 |
* |
44 |
* @author Josh Bloch |
45 |
* @author Neal Gafter |
46 |
* @version %I%, %G% |
47 |
* @see Map |
48 |
* @see Collection |
49 |
* @since 1.2 |
50 |
*/ |
51 |
|
52 |
public abstract class AbstractMap<K,V> implements Map<K,V> { |
53 |
/** |
54 |
* Sole constructor. (For invocation by subclass constructors, typically |
55 |
* implicit.) |
56 |
*/ |
57 |
protected AbstractMap() { |
58 |
} |
59 |
|
60 |
// Query Operations |
61 |
|
62 |
/** |
63 |
* {@inheritDoc} |
64 |
* |
65 |
* <p>This implementation returns <tt>entrySet().size()</tt>. |
66 |
*/ |
67 |
public int size() { |
68 |
return entrySet().size(); |
69 |
} |
70 |
|
71 |
/** |
72 |
* {@inheritDoc} |
73 |
* |
74 |
* <p>This implementation returns <tt>size() == 0</tt>. |
75 |
*/ |
76 |
public boolean isEmpty() { |
77 |
return size() == 0; |
78 |
} |
79 |
|
80 |
/** |
81 |
* {@inheritDoc} |
82 |
* |
83 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
84 |
* for an entry with the specified value. If such an entry is found, |
85 |
* <tt>true</tt> is returned. If the iteration terminates without |
86 |
* finding such an entry, <tt>false</tt> is returned. Note that this |
87 |
* implementation requires linear time in the size of the map. |
88 |
* |
89 |
* @throws ClassCastException {@inheritDoc} |
90 |
* @throws NullPointerException {@inheritDoc} |
91 |
*/ |
92 |
public boolean containsValue(Object value) { |
93 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
94 |
if (value==null) { |
95 |
while (i.hasNext()) { |
96 |
Entry<K,V> e = i.next(); |
97 |
if (e.getValue()==null) |
98 |
return true; |
99 |
} |
100 |
} else { |
101 |
while (i.hasNext()) { |
102 |
Entry<K,V> e = i.next(); |
103 |
if (value.equals(e.getValue())) |
104 |
return true; |
105 |
} |
106 |
} |
107 |
return false; |
108 |
} |
109 |
|
110 |
/** |
111 |
* {@inheritDoc} |
112 |
* |
113 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
114 |
* for an entry with the specified key. If such an entry is found, |
115 |
* <tt>true</tt> is returned. If the iteration terminates without |
116 |
* finding such an entry, <tt>false</tt> is returned. Note that this |
117 |
* implementation requires linear time in the size of the map; many |
118 |
* implementations will override this method. |
119 |
* |
120 |
* @throws ClassCastException {@inheritDoc} |
121 |
* @throws NullPointerException {@inheritDoc} |
122 |
*/ |
123 |
public boolean containsKey(Object key) { |
124 |
Iterator<Map.Entry<K,V>> i = entrySet().iterator(); |
125 |
if (key==null) { |
126 |
while (i.hasNext()) { |
127 |
Entry<K,V> e = i.next(); |
128 |
if (e.getKey()==null) |
129 |
return true; |
130 |
} |
131 |
} else { |
132 |
while (i.hasNext()) { |
133 |
Entry<K,V> e = i.next(); |
134 |
if (key.equals(e.getKey())) |
135 |
return true; |
136 |
} |
137 |
} |
138 |
return false; |
139 |
} |
140 |
|
141 |
/** |
142 |
* {@inheritDoc} |
143 |
* |
144 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
145 |
* for an entry with the specified key. If such an entry is found, |
146 |
* the entry's value is returned. If the iteration terminates without |
147 |
* finding such an entry, <tt>null</tt> is returned. Note that this |
148 |
* implementation requires linear time in the size of the map; many |
149 |
* implementations will override this method. |
150 |
* |
151 |
* @throws ClassCastException {@inheritDoc} |
152 |
* @throws NullPointerException {@inheritDoc} |
153 |
*/ |
154 |
public V get(Object key) { |
155 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
156 |
if (key==null) { |
157 |
while (i.hasNext()) { |
158 |
Entry<K,V> e = i.next(); |
159 |
if (e.getKey()==null) |
160 |
return e.getValue(); |
161 |
} |
162 |
} else { |
163 |
while (i.hasNext()) { |
164 |
Entry<K,V> e = i.next(); |
165 |
if (key.equals(e.getKey())) |
166 |
return e.getValue(); |
167 |
} |
168 |
} |
169 |
return null; |
170 |
} |
171 |
|
172 |
|
173 |
// Modification Operations |
174 |
|
175 |
/** |
176 |
* {@inheritDoc} |
177 |
* |
178 |
* <p>This implementation always throws an |
179 |
* <tt>UnsupportedOperationException</tt>. |
180 |
* |
181 |
* @throws UnsupportedOperationException {@inheritDoc} |
182 |
* @throws ClassCastException {@inheritDoc} |
183 |
* @throws NullPointerException {@inheritDoc} |
184 |
* @throws IllegalArgumentException {@inheritDoc} |
185 |
*/ |
186 |
public V put(K key, V value) { |
187 |
throw new UnsupportedOperationException(); |
188 |
} |
189 |
|
190 |
/** |
191 |
* {@inheritDoc} |
192 |
* |
193 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching for an |
194 |
* entry with the specified key. If such an entry is found, its value is |
195 |
* obtained with its <tt>getValue</tt> operation, the entry is removed |
196 |
* from the collection (and the backing map) with the iterator's |
197 |
* <tt>remove</tt> operation, and the saved value is returned. If the |
198 |
* iteration terminates without finding such an entry, <tt>null</tt> is |
199 |
* returned. Note that this implementation requires linear time in the |
200 |
* size of the map; many implementations will override this method. |
201 |
* |
202 |
* <p>Note that this implementation throws an |
203 |
* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
204 |
* iterator does not support the <tt>remove</tt> method and this map |
205 |
* contains a mapping for the specified key. |
206 |
* |
207 |
* @throws UnsupportedOperationException {@inheritDoc} |
208 |
* @throws ClassCastException {@inheritDoc} |
209 |
* @throws NullPointerException {@inheritDoc} |
210 |
*/ |
211 |
public V remove(Object key) { |
212 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
213 |
Entry<K,V> correctEntry = null; |
214 |
if (key==null) { |
215 |
while (correctEntry==null && i.hasNext()) { |
216 |
Entry<K,V> e = i.next(); |
217 |
if (e.getKey()==null) |
218 |
correctEntry = e; |
219 |
} |
220 |
} else { |
221 |
while (correctEntry==null && i.hasNext()) { |
222 |
Entry<K,V> e = i.next(); |
223 |
if (key.equals(e.getKey())) |
224 |
correctEntry = e; |
225 |
} |
226 |
} |
227 |
|
228 |
V oldValue = null; |
229 |
if (correctEntry !=null) { |
230 |
oldValue = correctEntry.getValue(); |
231 |
i.remove(); |
232 |
} |
233 |
return oldValue; |
234 |
} |
235 |
|
236 |
|
237 |
// Bulk Operations |
238 |
|
239 |
/** |
240 |
* {@inheritDoc} |
241 |
* |
242 |
* <p>This implementation iterates over the specified map's |
243 |
* <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt> |
244 |
* operation once for each entry returned by the iteration. |
245 |
* |
246 |
* <p>Note that this implementation throws an |
247 |
* <tt>UnsupportedOperationException</tt> if this map does not support |
248 |
* the <tt>put</tt> operation and the specified map is nonempty. |
249 |
* |
250 |
* @throws UnsupportedOperationException {@inheritDoc} |
251 |
* @throws ClassCastException {@inheritDoc} |
252 |
* @throws NullPointerException {@inheritDoc} |
253 |
* @throws IllegalArgumentException {@inheritDoc} |
254 |
*/ |
255 |
public void putAll(Map<? extends K, ? extends V> m) { |
256 |
Iterator<? extends Entry<? extends K, ? extends V>> i = m.entrySet().iterator(); |
257 |
while (i.hasNext()) { |
258 |
Entry<? extends K, ? extends V> e = i.next(); |
259 |
put(e.getKey(), e.getValue()); |
260 |
} |
261 |
} |
262 |
|
263 |
/** |
264 |
* {@inheritDoc} |
265 |
* |
266 |
* <p>This implementation calls <tt>entrySet().clear()</tt>. |
267 |
* |
268 |
* <p>Note that this implementation throws an |
269 |
* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
270 |
* does not support the <tt>clear</tt> operation. |
271 |
* |
272 |
* @throws UnsupportedOperationException {@inheritDoc} |
273 |
*/ |
274 |
public void clear() { |
275 |
entrySet().clear(); |
276 |
} |
277 |
|
278 |
|
279 |
// Views |
280 |
|
281 |
/** |
282 |
* Each of these fields are initialized to contain an instance of the |
283 |
* appropriate view the first time this view is requested. The views are |
284 |
* stateless, so there's no reason to create more than one of each. |
285 |
*/ |
286 |
transient volatile Set<K> keySet = null; |
287 |
transient volatile Collection<V> values = null; |
288 |
|
289 |
/** |
290 |
* {@inheritDoc} |
291 |
* |
292 |
* <p>This implementation returns a set that subclasses {@link AbstractSet}. |
293 |
* The subclass's iterator method returns a "wrapper object" over this |
294 |
* map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method |
295 |
* delegates to this map's <tt>size</tt> method and the |
296 |
* <tt>contains</tt> method delegates to this map's |
297 |
* <tt>containsKey</tt> method. |
298 |
* |
299 |
* <p>The set is created the first time this method is called, |
300 |
* and returned in response to all subsequent calls. No synchronization |
301 |
* is performed, so there is a slight chance that multiple calls to this |
302 |
* method will not all return the same set. |
303 |
*/ |
304 |
public Set<K> keySet() { |
305 |
if (keySet == null) { |
306 |
keySet = new AbstractSet<K>() { |
307 |
public Iterator<K> iterator() { |
308 |
return new Iterator<K>() { |
309 |
private Iterator<Entry<K,V>> i = entrySet().iterator(); |
310 |
|
311 |
public boolean hasNext() { |
312 |
return i.hasNext(); |
313 |
} |
314 |
|
315 |
public K next() { |
316 |
return i.next().getKey(); |
317 |
} |
318 |
|
319 |
public void remove() { |
320 |
i.remove(); |
321 |
} |
322 |
}; |
323 |
} |
324 |
|
325 |
public int size() { |
326 |
return AbstractMap.this.size(); |
327 |
} |
328 |
|
329 |
public boolean contains(Object k) { |
330 |
return AbstractMap.this.containsKey(k); |
331 |
} |
332 |
}; |
333 |
} |
334 |
return keySet; |
335 |
} |
336 |
|
337 |
/** |
338 |
* {@inheritDoc} |
339 |
* |
340 |
* <p>This implementation returns a collection that subclasses {@link |
341 |
* AbstractCollection}. The subclass's iterator method returns a |
342 |
* "wrapper object" over this map's <tt>entrySet()</tt> iterator. |
343 |
* The <tt>size</tt> method delegates to this map's <tt>size</tt> |
344 |
* method and the <tt>contains</tt> method delegates to this map's |
345 |
* <tt>containsValue</tt> method. |
346 |
* |
347 |
* <p>The collection is created the first time this method is called, and |
348 |
* returned in response to all subsequent calls. No synchronization is |
349 |
* performed, so there is a slight chance that multiple calls to this |
350 |
* method will not all return the same collection. |
351 |
*/ |
352 |
public Collection<V> values() { |
353 |
if (values == null) { |
354 |
values = new AbstractCollection<V>() { |
355 |
public Iterator<V> iterator() { |
356 |
return new Iterator<V>() { |
357 |
private Iterator<Entry<K,V>> i = entrySet().iterator(); |
358 |
|
359 |
public boolean hasNext() { |
360 |
return i.hasNext(); |
361 |
} |
362 |
|
363 |
public V next() { |
364 |
return i.next().getValue(); |
365 |
} |
366 |
|
367 |
public void remove() { |
368 |
i.remove(); |
369 |
} |
370 |
}; |
371 |
} |
372 |
|
373 |
public int size() { |
374 |
return AbstractMap.this.size(); |
375 |
} |
376 |
|
377 |
public boolean contains(Object v) { |
378 |
return AbstractMap.this.containsValue(v); |
379 |
} |
380 |
}; |
381 |
} |
382 |
return values; |
383 |
} |
384 |
|
385 |
public abstract Set<Entry<K,V>> entrySet(); |
386 |
|
387 |
|
388 |
// Comparison and hashing |
389 |
|
390 |
/** |
391 |
* Compares the specified object with this map for equality. Returns |
392 |
* <tt>true</tt> if the given object is also a map and the two maps |
393 |
* represent the same mappings. More formally, two maps <tt>m1</tt> and |
394 |
* <tt>m2</tt> represent the same mappings if |
395 |
* <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the |
396 |
* <tt>equals</tt> method works properly across different implementations |
397 |
* of the <tt>Map</tt> interface. |
398 |
* |
399 |
* <p>This implementation first checks if the specified object is this map; |
400 |
* if so it returns <tt>true</tt>. Then, it checks if the specified |
401 |
* object is a map whose size is identical to the size of this map; if |
402 |
* not, it returns <tt>false</tt>. If so, it iterates over this map's |
403 |
* <tt>entrySet</tt> collection, and checks that the specified map |
404 |
* contains each mapping that this map contains. If the specified map |
405 |
* fails to contain such a mapping, <tt>false</tt> is returned. If the |
406 |
* iteration completes, <tt>true</tt> is returned. |
407 |
* |
408 |
* @param o object to be compared for equality with this map |
409 |
* @return <tt>true</tt> if the specified object is equal to this map |
410 |
*/ |
411 |
public boolean equals(Object o) { |
412 |
if (o == this) |
413 |
return true; |
414 |
|
415 |
if (!(o instanceof Map)) |
416 |
return false; |
417 |
Map<K,V> m = (Map<K,V>) o; |
418 |
if (m.size() != size()) |
419 |
return false; |
420 |
|
421 |
try { |
422 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
423 |
while (i.hasNext()) { |
424 |
Entry<K,V> e = i.next(); |
425 |
K key = e.getKey(); |
426 |
V value = e.getValue(); |
427 |
if (value == null) { |
428 |
if (!(m.get(key)==null && m.containsKey(key))) |
429 |
return false; |
430 |
} else { |
431 |
if (!value.equals(m.get(key))) |
432 |
return false; |
433 |
} |
434 |
} |
435 |
} catch (ClassCastException unused) { |
436 |
return false; |
437 |
} catch (NullPointerException unused) { |
438 |
return false; |
439 |
} |
440 |
|
441 |
return true; |
442 |
} |
443 |
|
444 |
/** |
445 |
* Returns the hash code value for this map. The hash code of a map is |
446 |
* defined to be the sum of the hash codes of each entry in the map's |
447 |
* <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
448 |
* implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps |
449 |
* <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of |
450 |
* {@link Object#hashCode}. |
451 |
* |
452 |
* <p>This implementation iterates over <tt>entrySet()</tt>, calling |
453 |
* {@link Map.Entry#hashCode hashCode()} on each element (entry) in the |
454 |
* set, and adding up the results. |
455 |
* |
456 |
* @return the hash code value for this map |
457 |
* @see Map.Entry#hashCode() |
458 |
* @see Object#equals(Object) |
459 |
* @see Set#equals(Object) |
460 |
*/ |
461 |
public int hashCode() { |
462 |
int h = 0; |
463 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
464 |
while (i.hasNext()) |
465 |
h += i.next().hashCode(); |
466 |
return h; |
467 |
} |
468 |
|
469 |
/** |
470 |
* Returns a string representation of this map. The string representation |
471 |
* consists of a list of key-value mappings in the order returned by the |
472 |
* map's <tt>entrySet</tt> view's iterator, enclosed in braces |
473 |
* (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
474 |
* <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
475 |
* the key followed by an equals sign (<tt>"="</tt>) followed by the |
476 |
* associated value. Keys and values are converted to strings as by |
477 |
* <tt>String.valueOf(Object)</tt>.<p> |
478 |
* |
479 |
* This implementation creates an empty string buffer, appends a left |
480 |
* brace, and iterates over the map's <tt>entrySet</tt> view, appending |
481 |
* the string representation of each <tt>map.entry</tt> in turn. After |
482 |
* appending each entry except the last, the string <tt>", "</tt> is |
483 |
* appended. Finally a right brace is appended. A string is obtained |
484 |
* from the stringbuffer, and returned. |
485 |
* |
486 |
* @return a String representation of this map |
487 |
*/ |
488 |
public String toString() { |
489 |
StringBuilder sb = new StringBuilder(); |
490 |
sb.append("{"); |
491 |
|
492 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
493 |
boolean hasNext = i.hasNext(); |
494 |
while (hasNext) { |
495 |
Entry<K,V> e = i.next(); |
496 |
K key = e.getKey(); |
497 |
V value = e.getValue(); |
498 |
if (key == this) |
499 |
sb.append("(this Map)"); |
500 |
else |
501 |
sb.append(key); |
502 |
sb.append("="); |
503 |
if (value == this) |
504 |
sb.append("(this Map)"); |
505 |
else |
506 |
sb.append(value); |
507 |
hasNext = i.hasNext(); |
508 |
if (hasNext) |
509 |
sb.append(", "); |
510 |
} |
511 |
|
512 |
sb.append("}"); |
513 |
return sb.toString(); |
514 |
} |
515 |
|
516 |
/** |
517 |
* Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
518 |
* and values themselves are not cloned. |
519 |
* |
520 |
* @return a shallow copy of this map |
521 |
*/ |
522 |
protected Object clone() throws CloneNotSupportedException { |
523 |
AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone(); |
524 |
result.keySet = null; |
525 |
result.values = null; |
526 |
return result; |
527 |
} |
528 |
|
529 |
/** |
530 |
* Utility method for SimpleEntry and SimpleImmutableEntry. |
531 |
* Test for equality, checking for nulls. |
532 |
*/ |
533 |
private static boolean eq(Object o1, Object o2) { |
534 |
return o1 == null ? o2 == null : o1.equals(o2); |
535 |
} |
536 |
|
537 |
// Implementation Note: SimpleEntry and SimpleImmutableEntry |
538 |
// are distinct unrelated classes, even though they share |
539 |
// some code. Since you can't add or subtract final-ness |
540 |
// of a field in a subclass, they can't share representations, |
541 |
// and the amount of duplicated code is too small to warrant |
542 |
// exposing a common abstract class. |
543 |
|
544 |
|
545 |
/** |
546 |
* An Entry maintaining a key and a value. The value may be |
547 |
* changed using the <tt>setValue</tt> method. This class |
548 |
* facilitates the process of building custom map |
549 |
* implementations. For example, it may be convenient to return |
550 |
* arrays of <tt>SimpleEntry</tt> instances in method |
551 |
* <tt>Map.entrySet().toArray</tt>. |
552 |
* |
553 |
* @since 1.6 |
554 |
*/ |
555 |
public static class SimpleEntry<K,V> |
556 |
implements Entry<K,V>, java.io.Serializable |
557 |
{ |
558 |
private static final long serialVersionUID = -8499721149061103585L; |
559 |
|
560 |
private final K key; |
561 |
private V value; |
562 |
|
563 |
/** |
564 |
* Creates an entry representing a mapping from the specified |
565 |
* key to the specified value. |
566 |
* |
567 |
* @param key the key represented by this entry |
568 |
* @param value the value represented by this entry |
569 |
*/ |
570 |
public SimpleEntry(K key, V value) { |
571 |
this.key = key; |
572 |
this.value = value; |
573 |
} |
574 |
|
575 |
/** |
576 |
* Creates an entry representing the same mapping as the |
577 |
* specified entry. |
578 |
* |
579 |
* @param entry the entry to copy |
580 |
*/ |
581 |
public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
582 |
this.key = entry.getKey(); |
583 |
this.value = entry.getValue(); |
584 |
} |
585 |
|
586 |
/** |
587 |
* Returns the key corresponding to this entry. |
588 |
* |
589 |
* @return the key corresponding to this entry |
590 |
*/ |
591 |
public K getKey() { |
592 |
return key; |
593 |
} |
594 |
|
595 |
/** |
596 |
* Returns the value corresponding to this entry. |
597 |
* |
598 |
* @return the value corresponding to this entry |
599 |
*/ |
600 |
public V getValue() { |
601 |
return value; |
602 |
} |
603 |
|
604 |
/** |
605 |
* Replaces the value corresponding to this entry with the specified |
606 |
* value. |
607 |
* |
608 |
* @param value new value to be stored in this entry |
609 |
* @return the old value corresponding to the entry |
610 |
*/ |
611 |
public V setValue(V value) { |
612 |
V oldValue = this.value; |
613 |
this.value = value; |
614 |
return oldValue; |
615 |
} |
616 |
|
617 |
public boolean equals(Object o) { |
618 |
if (!(o instanceof Map.Entry)) |
619 |
return false; |
620 |
Map.Entry e = (Map.Entry)o; |
621 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
622 |
} |
623 |
|
624 |
public int hashCode() { |
625 |
return (key == null ? 0 : key.hashCode()) ^ |
626 |
(value == null ? 0 : value.hashCode()); |
627 |
} |
628 |
|
629 |
/** |
630 |
* Returns a String representation of this map entry. This |
631 |
* implementation returns the string representation of this |
632 |
* entry's key followed by the equals character ("<tt>=</tt>") |
633 |
* followed by the string representation of this entry's value. |
634 |
* |
635 |
* @return a String representation of this map entry |
636 |
*/ |
637 |
public String toString() { |
638 |
return key + "=" + value; |
639 |
} |
640 |
|
641 |
} |
642 |
|
643 |
/** |
644 |
* An Entry maintaining an immutable key and value. This class |
645 |
* does not support method <tt>setValue</tt>. This class may be |
646 |
* convenient in methods that return thread-safe snapshots of |
647 |
* key-value mappings. |
648 |
* |
649 |
* @since 1.6 |
650 |
*/ |
651 |
public static class SimpleImmutableEntry<K,V> |
652 |
implements Entry<K,V>, java.io.Serializable |
653 |
{ |
654 |
private static final long serialVersionUID = 7138329143949025153L; |
655 |
|
656 |
private final K key; |
657 |
private final V value; |
658 |
|
659 |
/** |
660 |
* Creates an entry representing a mapping from the specified |
661 |
* key to the specified value. |
662 |
* |
663 |
* @param key the key represented by this entry |
664 |
* @param value the value represented by this entry |
665 |
*/ |
666 |
public SimpleImmutableEntry(K key, V value) { |
667 |
this.key = key; |
668 |
this.value = value; |
669 |
} |
670 |
|
671 |
/** |
672 |
* Creates an entry representing the same mapping as the |
673 |
* specified entry. |
674 |
* |
675 |
* @param entry the entry to copy |
676 |
*/ |
677 |
public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
678 |
this.key = entry.getKey(); |
679 |
this.value = entry.getValue(); |
680 |
} |
681 |
|
682 |
/** |
683 |
* Returns the key corresponding to this entry. |
684 |
* |
685 |
* @return the key corresponding to this entry |
686 |
*/ |
687 |
public K getKey() { |
688 |
return key; |
689 |
} |
690 |
|
691 |
/** |
692 |
* Returns the value corresponding to this entry. |
693 |
* |
694 |
* @return the value corresponding to this entry |
695 |
*/ |
696 |
public V getValue() { |
697 |
return value; |
698 |
} |
699 |
|
700 |
/** |
701 |
* Replaces the value corresponding to this entry with the specified |
702 |
* value (optional operation). This implementation simply throws |
703 |
* <tt>UnsupportedOperationException</tt>, as this class implements |
704 |
* an <i>immutable</i> map entry. |
705 |
* |
706 |
* @param value new value to be stored in this entry |
707 |
* @return (Does not return) |
708 |
* @throws UnsupportedOperationException always |
709 |
*/ |
710 |
public V setValue(V value) { |
711 |
throw new UnsupportedOperationException(); |
712 |
} |
713 |
|
714 |
public boolean equals(Object o) { |
715 |
if (!(o instanceof Map.Entry)) |
716 |
return false; |
717 |
Map.Entry e = (Map.Entry)o; |
718 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
719 |
} |
720 |
|
721 |
public int hashCode() { |
722 |
return (key == null ? 0 : key.hashCode()) ^ |
723 |
(value == null ? 0 : value.hashCode()); |
724 |
} |
725 |
|
726 |
/** |
727 |
* Returns a String representation of this map entry. This |
728 |
* implementation returns the string representation of this |
729 |
* entry's key followed by the equals character ("<tt>=</tt>") |
730 |
* followed by the string representation of this entry's value. |
731 |
* |
732 |
* @return a String representation of this map entry |
733 |
*/ |
734 |
public String toString() { |
735 |
return key + "=" + value; |
736 |
} |
737 |
|
738 |
} |
739 |
|
740 |
} |