1 |
/* |
2 |
* Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved. |
3 |
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 |
* |
5 |
* This code is free software; you can redistribute it and/or modify it |
6 |
* under the terms of the GNU General Public License version 2 only, as |
7 |
* published by the Free Software Foundation. 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; |
27 |
import java.util.Map.Entry; |
28 |
|
29 |
/** |
30 |
* This class provides a skeletal implementation of the <tt>Map</tt> |
31 |
* interface, to minimize the effort required to implement this interface. |
32 |
* |
33 |
* <p>To implement an unmodifiable map, the programmer needs only to extend this |
34 |
* class and provide an implementation for the <tt>entrySet</tt> method, which |
35 |
* returns a set-view of the map's mappings. Typically, the returned set |
36 |
* will, in turn, be implemented atop <tt>AbstractSet</tt>. This set should |
37 |
* not support the <tt>add</tt> or <tt>remove</tt> methods, and its iterator |
38 |
* should not support the <tt>remove</tt> method. |
39 |
* |
40 |
* <p>To implement a modifiable map, the programmer must additionally override |
41 |
* this class's <tt>put</tt> method (which otherwise throws an |
42 |
* <tt>UnsupportedOperationException</tt>), and the iterator returned by |
43 |
* <tt>entrySet().iterator()</tt> must additionally implement its |
44 |
* <tt>remove</tt> method. |
45 |
* |
46 |
* <p>The programmer should generally provide a void (no argument) and map |
47 |
* constructor, as per the recommendation in the <tt>Map</tt> interface |
48 |
* specification. |
49 |
* |
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}/../technotes/guides/collections/index.html"> |
56 |
* Java Collections Framework</a>. |
57 |
* |
58 |
* @param <K> the type of keys maintained by this map |
59 |
* @param <V> the type of mapped values |
60 |
* |
61 |
* @author Josh Bloch |
62 |
* @author Neal Gafter |
63 |
* @version %I%, %G% |
64 |
* @see Map |
65 |
* @see Collection |
66 |
* @since 1.2 |
67 |
*/ |
68 |
|
69 |
public abstract class AbstractMap<K,V> implements Map<K,V> { |
70 |
/** |
71 |
* Sole constructor. (For invocation by subclass constructors, typically |
72 |
* implicit.) |
73 |
*/ |
74 |
protected AbstractMap() { |
75 |
} |
76 |
|
77 |
// Query Operations |
78 |
|
79 |
/** |
80 |
* {@inheritDoc} |
81 |
* |
82 |
* <p>This implementation returns <tt>entrySet().size()</tt>. |
83 |
*/ |
84 |
public int size() { |
85 |
return entrySet().size(); |
86 |
} |
87 |
|
88 |
/** |
89 |
* {@inheritDoc} |
90 |
* |
91 |
* <p>This implementation returns <tt>size() == 0</tt>. |
92 |
*/ |
93 |
public boolean isEmpty() { |
94 |
return size() == 0; |
95 |
} |
96 |
|
97 |
/** |
98 |
* {@inheritDoc} |
99 |
* |
100 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
101 |
* for an entry with the specified value. If such an entry is found, |
102 |
* <tt>true</tt> is returned. If the iteration terminates without |
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 |
* |
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; |
125 |
} |
126 |
|
127 |
/** |
128 |
* {@inheritDoc} |
129 |
* |
130 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
131 |
* for an entry with the specified key. If such an entry is found, |
132 |
* <tt>true</tt> is returned. If the iteration terminates without |
133 |
* finding such an entry, <tt>false</tt> is returned. Note that this |
134 |
* implementation requires linear time in the size of the map; many |
135 |
* implementations will override this method. |
136 |
* |
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; |
156 |
} |
157 |
|
158 |
/** |
159 |
* {@inheritDoc} |
160 |
* |
161 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching |
162 |
* for an entry with the specified key. If such an entry is found, |
163 |
* the entry's value is returned. If the iteration terminates without |
164 |
* finding such an entry, <tt>null</tt> is returned. Note that this |
165 |
* implementation requires linear time in the size of the map; many |
166 |
* implementations will override this method. |
167 |
* |
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; |
187 |
} |
188 |
|
189 |
|
190 |
// Modification Operations |
191 |
|
192 |
/** |
193 |
* {@inheritDoc} |
194 |
* |
195 |
* <p>This implementation always throws an |
196 |
* <tt>UnsupportedOperationException</tt>. |
197 |
* |
198 |
* @throws UnsupportedOperationException {@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(); |
205 |
} |
206 |
|
207 |
/** |
208 |
* {@inheritDoc} |
209 |
* |
210 |
* <p>This implementation iterates over <tt>entrySet()</tt> searching for an |
211 |
* entry with the specified key. If such an entry is found, its value is |
212 |
* obtained with its <tt>getValue</tt> operation, the entry is removed |
213 |
* from the collection (and the backing map) with the iterator's |
214 |
* <tt>remove</tt> operation, and the saved value is returned. If the |
215 |
* iteration terminates without finding such an entry, <tt>null</tt> is |
216 |
* returned. Note that this implementation requires linear time in the |
217 |
* size of the map; many implementations will override this method. |
218 |
* |
219 |
* <p>Note that this implementation throws an |
220 |
* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
221 |
* iterator does not support the <tt>remove</tt> method and this map |
222 |
* contains a mapping for the specified key. |
223 |
* |
224 |
* @throws UnsupportedOperationException {@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; |
251 |
} |
252 |
|
253 |
|
254 |
// Bulk Operations |
255 |
|
256 |
/** |
257 |
* {@inheritDoc} |
258 |
* |
259 |
* <p>This implementation iterates over the specified map's |
260 |
* <tt>entrySet()</tt> collection, and calls this map's <tt>put</tt> |
261 |
* operation once for each entry returned by the iteration. |
262 |
* |
263 |
* <p>Note that this implementation throws an |
264 |
* <tt>UnsupportedOperationException</tt> if this map does not support |
265 |
* the <tt>put</tt> operation and the specified map is nonempty. |
266 |
* |
267 |
* @throws UnsupportedOperationException {@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 |
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
274 |
put(e.getKey(), e.getValue()); |
275 |
} |
276 |
|
277 |
/** |
278 |
* {@inheritDoc} |
279 |
* |
280 |
* <p>This implementation calls <tt>entrySet().clear()</tt>. |
281 |
* |
282 |
* <p>Note that this implementation throws an |
283 |
* <tt>UnsupportedOperationException</tt> if the <tt>entrySet</tt> |
284 |
* does not support the <tt>clear</tt> operation. |
285 |
* |
286 |
* @throws UnsupportedOperationException {@inheritDoc} |
287 |
*/ |
288 |
public void clear() { |
289 |
entrySet().clear(); |
290 |
} |
291 |
|
292 |
|
293 |
// Views |
294 |
|
295 |
/** |
296 |
* Each of these fields are initialized to contain an instance of the |
297 |
* appropriate view the first time this view is requested. The views are |
298 |
* stateless, so there's no reason to create more than one of each. |
299 |
*/ |
300 |
transient volatile Set<K> keySet = null; |
301 |
transient volatile Collection<V> values = null; |
302 |
|
303 |
/** |
304 |
* {@inheritDoc} |
305 |
* |
306 |
* <p>This implementation returns a set that subclasses {@link AbstractSet}. |
307 |
* The subclass's iterator method returns a "wrapper object" over this |
308 |
* map's <tt>entrySet()</tt> iterator. The <tt>size</tt> method |
309 |
* delegates to this map's <tt>size</tt> method and the |
310 |
* <tt>contains</tt> method delegates to this map's |
311 |
* <tt>containsKey</tt> method. |
312 |
* |
313 |
* <p>The set is created the first time this method is called, |
314 |
* and returned in response to all subsequent calls. No synchronization |
315 |
* is performed, so there is a slight chance that multiple calls to this |
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 |
} |
336 |
}; |
337 |
} |
338 |
|
339 |
public int size() { |
340 |
return AbstractMap.this.size(); |
341 |
} |
342 |
|
343 |
public boolean contains(Object k) { |
344 |
return AbstractMap.this.containsKey(k); |
345 |
} |
346 |
}; |
347 |
} |
348 |
return keySet; |
349 |
} |
350 |
|
351 |
/** |
352 |
* {@inheritDoc} |
353 |
* |
354 |
* <p>This implementation returns a collection that subclasses {@link |
355 |
* AbstractCollection}. The subclass's iterator method returns a |
356 |
* "wrapper object" over this map's <tt>entrySet()</tt> iterator. |
357 |
* The <tt>size</tt> method delegates to this map's <tt>size</tt> |
358 |
* method and the <tt>contains</tt> method delegates to this map's |
359 |
* <tt>containsValue</tt> method. |
360 |
* |
361 |
* <p>The collection is created the first time this method is called, and |
362 |
* returned in response to all subsequent calls. No synchronization is |
363 |
* performed, so there is a slight chance that multiple calls to this |
364 |
* method will not all return the same collection. |
365 |
*/ |
366 |
public Collection<V> values() { |
367 |
if (values == null) { |
368 |
values = new AbstractCollection<V>() { |
369 |
public Iterator<V> iterator() { |
370 |
return new Iterator<V>() { |
371 |
private Iterator<Entry<K,V>> i = entrySet().iterator(); |
372 |
|
373 |
public boolean hasNext() { |
374 |
return i.hasNext(); |
375 |
} |
376 |
|
377 |
public V next() { |
378 |
return i.next().getValue(); |
379 |
} |
380 |
|
381 |
public void remove() { |
382 |
i.remove(); |
383 |
} |
384 |
}; |
385 |
} |
386 |
|
387 |
public int size() { |
388 |
return AbstractMap.this.size(); |
389 |
} |
390 |
|
391 |
public boolean contains(Object v) { |
392 |
return AbstractMap.this.containsValue(v); |
393 |
} |
394 |
}; |
395 |
} |
396 |
return values; |
397 |
} |
398 |
|
399 |
public abstract Set<Entry<K,V>> entrySet(); |
400 |
|
401 |
|
402 |
// Comparison and hashing |
403 |
|
404 |
/** |
405 |
* Compares the specified object with this map for equality. Returns |
406 |
* <tt>true</tt> if the given object is also a map and the two maps |
407 |
* represent the same mappings. More formally, two maps <tt>m1</tt> and |
408 |
* <tt>m2</tt> represent the same mappings if |
409 |
* <tt>m1.entrySet().equals(m2.entrySet())</tt>. This ensures that the |
410 |
* <tt>equals</tt> method works properly across different implementations |
411 |
* of the <tt>Map</tt> interface. |
412 |
* |
413 |
* <p>This implementation first checks if the specified object is this map; |
414 |
* if so it returns <tt>true</tt>. Then, it checks if the specified |
415 |
* object is a map whose size is identical to the size of this map; if |
416 |
* not, it returns <tt>false</tt>. If so, it iterates over this map's |
417 |
* <tt>entrySet</tt> collection, and checks that the specified map |
418 |
* contains each mapping that this map contains. If the specified map |
419 |
* fails to contain such a mapping, <tt>false</tt> is returned. If the |
420 |
* iteration completes, <tt>true</tt> is returned. |
421 |
* |
422 |
* @param o object to be compared for equality with this map |
423 |
* @return <tt>true</tt> if the specified object is equal to this map |
424 |
*/ |
425 |
public boolean equals(Object o) { |
426 |
if (o == this) |
427 |
return true; |
428 |
|
429 |
if (!(o instanceof Map)) |
430 |
return false; |
431 |
Map<K,V> m = (Map<K,V>) o; |
432 |
if (m.size() != size()) |
433 |
return false; |
434 |
|
435 |
try { |
436 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
437 |
while (i.hasNext()) { |
438 |
Entry<K,V> e = i.next(); |
439 |
K key = e.getKey(); |
440 |
V value = e.getValue(); |
441 |
if (value == null) { |
442 |
if (!(m.get(key)==null && m.containsKey(key))) |
443 |
return false; |
444 |
} else { |
445 |
if (!value.equals(m.get(key))) |
446 |
return false; |
447 |
} |
448 |
} |
449 |
} catch (ClassCastException unused) { |
450 |
return false; |
451 |
} catch (NullPointerException unused) { |
452 |
return false; |
453 |
} |
454 |
|
455 |
return true; |
456 |
} |
457 |
|
458 |
/** |
459 |
* Returns the hash code value for this map. The hash code of a map is |
460 |
* defined to be the sum of the hash codes of each entry in the map's |
461 |
* <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
462 |
* implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two maps |
463 |
* <tt>m1</tt> and <tt>m2</tt>, as required by the general contract of |
464 |
* {@link Object#hashCode}. |
465 |
* |
466 |
* <p>This implementation iterates over <tt>entrySet()</tt>, calling |
467 |
* {@link Map.Entry#hashCode hashCode()} on each element (entry) in the |
468 |
* set, and adding up the results. |
469 |
* |
470 |
* @return the hash code value for this map |
471 |
* @see Map.Entry#hashCode() |
472 |
* @see Object#equals(Object) |
473 |
* @see Set#equals(Object) |
474 |
*/ |
475 |
public int hashCode() { |
476 |
int h = 0; |
477 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
478 |
while (i.hasNext()) |
479 |
h += i.next().hashCode(); |
480 |
return h; |
481 |
} |
482 |
|
483 |
/** |
484 |
* Returns a string representation of this map. The string representation |
485 |
* consists of a list of key-value mappings in the order returned by the |
486 |
* map's <tt>entrySet</tt> view's iterator, enclosed in braces |
487 |
* (<tt>"{}"</tt>). Adjacent mappings are separated by the characters |
488 |
* <tt>", "</tt> (comma and space). Each key-value mapping is rendered as |
489 |
* the key followed by an equals sign (<tt>"="</tt>) followed by the |
490 |
* associated value. Keys and values are converted to strings as by |
491 |
* {@link String#valueOf(Object)}. |
492 |
* |
493 |
* @return a string representation of this map |
494 |
*/ |
495 |
public String toString() { |
496 |
Iterator<Entry<K,V>> i = entrySet().iterator(); |
497 |
if (! i.hasNext()) |
498 |
return "{}"; |
499 |
|
500 |
StringBuilder sb = new StringBuilder(); |
501 |
sb.append('{'); |
502 |
for (;;) { |
503 |
Entry<K,V> e = i.next(); |
504 |
K key = e.getKey(); |
505 |
V value = e.getValue(); |
506 |
sb.append(key == this ? "(this Map)" : key); |
507 |
sb.append('='); |
508 |
sb.append(value == this ? "(this Map)" : value); |
509 |
if (! i.hasNext()) |
510 |
return sb.append('}').toString(); |
511 |
sb.append(", "); |
512 |
} |
513 |
} |
514 |
|
515 |
/** |
516 |
* Returns a shallow copy of this <tt>AbstractMap</tt> instance: the keys |
517 |
* and values themselves are not cloned. |
518 |
* |
519 |
* @return a shallow copy of this map |
520 |
*/ |
521 |
protected Object clone() throws CloneNotSupportedException { |
522 |
AbstractMap<K,V> result = (AbstractMap<K,V>)super.clone(); |
523 |
result.keySet = null; |
524 |
result.values = null; |
525 |
return result; |
526 |
} |
527 |
|
528 |
/** |
529 |
* Utility method for SimpleEntry and SimpleImmutableEntry. |
530 |
* Test for equality, checking for nulls. |
531 |
*/ |
532 |
private static boolean eq(Object o1, Object o2) { |
533 |
return o1 == null ? o2 == null : o1.equals(o2); |
534 |
} |
535 |
|
536 |
// Implementation Note: SimpleEntry and SimpleImmutableEntry |
537 |
// are distinct unrelated classes, even though they share |
538 |
// some code. Since you can't add or subtract final-ness |
539 |
// of a field in a subclass, they can't share representations, |
540 |
// and the amount of duplicated code is too small to warrant |
541 |
// exposing a common abstract class. |
542 |
|
543 |
|
544 |
/** |
545 |
* An Entry maintaining a key and a value. The value may be |
546 |
* changed using the <tt>setValue</tt> method. This class |
547 |
* facilitates the process of building custom map |
548 |
* implementations. For example, it may be convenient to return |
549 |
* arrays of <tt>SimpleEntry</tt> instances in method |
550 |
* <tt>Map.entrySet().toArray</tt>. |
551 |
* |
552 |
* @since 1.6 |
553 |
*/ |
554 |
public static class SimpleEntry<K,V> |
555 |
implements Entry<K,V>, java.io.Serializable |
556 |
{ |
557 |
private static final long serialVersionUID = -8499721149061103585L; |
558 |
|
559 |
private final K key; |
560 |
private V value; |
561 |
|
562 |
/** |
563 |
* Creates an entry representing a mapping from the specified |
564 |
* key to the specified value. |
565 |
* |
566 |
* @param key the key represented by this entry |
567 |
* @param value the value represented by this entry |
568 |
*/ |
569 |
public SimpleEntry(K key, V value) { |
570 |
this.key = key; |
571 |
this.value = value; |
572 |
} |
573 |
|
574 |
/** |
575 |
* Creates an entry representing the same mapping as the |
576 |
* specified entry. |
577 |
* |
578 |
* @param entry the entry to copy |
579 |
*/ |
580 |
public SimpleEntry(Entry<? extends K, ? extends V> entry) { |
581 |
this.key = entry.getKey(); |
582 |
this.value = entry.getValue(); |
583 |
} |
584 |
|
585 |
/** |
586 |
* Returns the key corresponding to this entry. |
587 |
* |
588 |
* @return the key corresponding to this entry |
589 |
*/ |
590 |
public K getKey() { |
591 |
return key; |
592 |
} |
593 |
|
594 |
/** |
595 |
* Returns the value corresponding to this entry. |
596 |
* |
597 |
* @return the value corresponding to this entry |
598 |
*/ |
599 |
public V getValue() { |
600 |
return value; |
601 |
} |
602 |
|
603 |
/** |
604 |
* Replaces the value corresponding to this entry with the specified |
605 |
* value. |
606 |
* |
607 |
* @param value new value to be stored in this entry |
608 |
* @return the old value corresponding to the entry |
609 |
*/ |
610 |
public V setValue(V value) { |
611 |
V oldValue = this.value; |
612 |
this.value = value; |
613 |
return oldValue; |
614 |
} |
615 |
|
616 |
/** |
617 |
* Compares the specified object with this entry for equality. |
618 |
* Returns {@code true} if the given object is also a map entry and |
619 |
* the two entries represent the same mapping. More formally, two |
620 |
* entries {@code e1} and {@code e2} represent the same mapping |
621 |
* if<pre> |
622 |
* (e1.getKey()==null ? |
623 |
* e2.getKey()==null : |
624 |
* e1.getKey().equals(e2.getKey())) |
625 |
* && |
626 |
* (e1.getValue()==null ? |
627 |
* e2.getValue()==null : |
628 |
* e1.getValue().equals(e2.getValue()))</pre> |
629 |
* This ensures that the {@code equals} method works properly across |
630 |
* different implementations of the {@code Map.Entry} interface. |
631 |
* |
632 |
* @param o object to be compared for equality with this map entry |
633 |
* @return {@code true} if the specified object is equal to this map |
634 |
* entry |
635 |
* @see #hashCode |
636 |
*/ |
637 |
public boolean equals(Object o) { |
638 |
if (!(o instanceof Map.Entry)) |
639 |
return false; |
640 |
Map.Entry e = (Map.Entry)o; |
641 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
642 |
} |
643 |
|
644 |
/** |
645 |
* Returns the hash code value for this map entry. The hash code |
646 |
* of a map entry {@code e} is defined to be: <pre> |
647 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
648 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
649 |
* This ensures that {@code e1.equals(e2)} implies that |
650 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
651 |
* {@code e1} and {@code e2}, as required by the general |
652 |
* contract of {@link Object#hashCode}. |
653 |
* |
654 |
* @return the hash code value for this map entry |
655 |
* @see #equals |
656 |
*/ |
657 |
public int hashCode() { |
658 |
return (key == null ? 0 : key.hashCode()) ^ |
659 |
(value == null ? 0 : value.hashCode()); |
660 |
} |
661 |
|
662 |
/** |
663 |
* Returns a String representation of this map entry. This |
664 |
* implementation returns the string representation of this |
665 |
* entry's key followed by the equals character ("<tt>=</tt>") |
666 |
* followed by the string representation of this entry's value. |
667 |
* |
668 |
* @return a String representation of this map entry |
669 |
*/ |
670 |
public String toString() { |
671 |
return key + "=" + value; |
672 |
} |
673 |
|
674 |
} |
675 |
|
676 |
/** |
677 |
* An Entry maintaining an immutable key and value. This class |
678 |
* does not support method <tt>setValue</tt>. This class may be |
679 |
* convenient in methods that return thread-safe snapshots of |
680 |
* key-value mappings. |
681 |
* |
682 |
* @since 1.6 |
683 |
*/ |
684 |
public static class SimpleImmutableEntry<K,V> |
685 |
implements Entry<K,V>, java.io.Serializable |
686 |
{ |
687 |
private static final long serialVersionUID = 7138329143949025153L; |
688 |
|
689 |
private final K key; |
690 |
private final V value; |
691 |
|
692 |
/** |
693 |
* Creates an entry representing a mapping from the specified |
694 |
* key to the specified value. |
695 |
* |
696 |
* @param key the key represented by this entry |
697 |
* @param value the value represented by this entry |
698 |
*/ |
699 |
public SimpleImmutableEntry(K key, V value) { |
700 |
this.key = key; |
701 |
this.value = value; |
702 |
} |
703 |
|
704 |
/** |
705 |
* Creates an entry representing the same mapping as the |
706 |
* specified entry. |
707 |
* |
708 |
* @param entry the entry to copy |
709 |
*/ |
710 |
public SimpleImmutableEntry(Entry<? extends K, ? extends V> entry) { |
711 |
this.key = entry.getKey(); |
712 |
this.value = entry.getValue(); |
713 |
} |
714 |
|
715 |
/** |
716 |
* Returns the key corresponding to this entry. |
717 |
* |
718 |
* @return the key corresponding to this entry |
719 |
*/ |
720 |
public K getKey() { |
721 |
return key; |
722 |
} |
723 |
|
724 |
/** |
725 |
* Returns the value corresponding to this entry. |
726 |
* |
727 |
* @return the value corresponding to this entry |
728 |
*/ |
729 |
public V getValue() { |
730 |
return value; |
731 |
} |
732 |
|
733 |
/** |
734 |
* Replaces the value corresponding to this entry with the specified |
735 |
* value (optional operation). This implementation simply throws |
736 |
* <tt>UnsupportedOperationException</tt>, as this class implements |
737 |
* an <i>immutable</i> map entry. |
738 |
* |
739 |
* @param value new value to be stored in this entry |
740 |
* @return (Does not return) |
741 |
* @throws UnsupportedOperationException always |
742 |
*/ |
743 |
public V setValue(V value) { |
744 |
throw new UnsupportedOperationException(); |
745 |
} |
746 |
|
747 |
/** |
748 |
* Compares the specified object with this entry for equality. |
749 |
* Returns {@code true} if the given object is also a map entry and |
750 |
* the two entries represent the same mapping. More formally, two |
751 |
* entries {@code e1} and {@code e2} represent the same mapping |
752 |
* if<pre> |
753 |
* (e1.getKey()==null ? |
754 |
* e2.getKey()==null : |
755 |
* e1.getKey().equals(e2.getKey())) |
756 |
* && |
757 |
* (e1.getValue()==null ? |
758 |
* e2.getValue()==null : |
759 |
* e1.getValue().equals(e2.getValue()))</pre> |
760 |
* This ensures that the {@code equals} method works properly across |
761 |
* different implementations of the {@code Map.Entry} interface. |
762 |
* |
763 |
* @param o object to be compared for equality with this map entry |
764 |
* @return {@code true} if the specified object is equal to this map |
765 |
* entry |
766 |
* @see #hashCode |
767 |
*/ |
768 |
public boolean equals(Object o) { |
769 |
if (!(o instanceof Map.Entry)) |
770 |
return false; |
771 |
Map.Entry e = (Map.Entry)o; |
772 |
return eq(key, e.getKey()) && eq(value, e.getValue()); |
773 |
} |
774 |
|
775 |
/** |
776 |
* Returns the hash code value for this map entry. The hash code |
777 |
* of a map entry {@code e} is defined to be: <pre> |
778 |
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^ |
779 |
* (e.getValue()==null ? 0 : e.getValue().hashCode())</pre> |
780 |
* This ensures that {@code e1.equals(e2)} implies that |
781 |
* {@code e1.hashCode()==e2.hashCode()} for any two Entries |
782 |
* {@code e1} and {@code e2}, as required by the general |
783 |
* contract of {@link Object#hashCode}. |
784 |
* |
785 |
* @return the hash code value for this map entry |
786 |
* @see #equals |
787 |
*/ |
788 |
public int hashCode() { |
789 |
return (key == null ? 0 : key.hashCode()) ^ |
790 |
(value == null ? 0 : value.hashCode()); |
791 |
} |
792 |
|
793 |
/** |
794 |
* Returns a String representation of this map entry. This |
795 |
* implementation returns the string representation of this |
796 |
* entry's key followed by the equals character ("<tt>=</tt>") |
797 |
* followed by the string representation of this entry's value. |
798 |
* |
799 |
* @return a String representation of this map entry |
800 |
*/ |
801 |
public String toString() { |
802 |
return key + "=" + value; |
803 |
} |
804 |
|
805 |
} |
806 |
|
807 |
} |