1 |
dl |
1.1 |
/* |
2 |
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
|
|
* Expert Group and released to the public domain, as explained at |
4 |
|
|
* http://creativecommons.org/licenses/publicdomain |
5 |
|
|
*/ |
6 |
|
|
|
7 |
|
|
package jsr166x; |
8 |
|
|
|
9 |
|
|
import java.util.*; |
10 |
|
|
import java.util.concurrent.*; |
11 |
|
|
|
12 |
|
|
/** |
13 |
dl |
1.2 |
* A scalable concurrent {@link NavigableSet} implementation based on |
14 |
|
|
* a {@link ConcurrentSkipListMap}. This class maintains a set in |
15 |
|
|
* ascending order, sorted according to the <i>natural order</i> for |
16 |
|
|
* the element's class (see {@link Comparable}), or by the comparator |
17 |
|
|
* provided at creation time, depending on which constructor is |
18 |
|
|
* used.<p> |
19 |
dl |
1.1 |
* |
20 |
|
|
* This implementation provides expected average <i>log(n)</i> time |
21 |
|
|
* cost for the <tt>contains</tt>, <tt>add</tt>, and <tt>remove</tt> |
22 |
|
|
* operations and their variants. Insertion, removal, and access |
23 |
|
|
* operations safely execute concurrently by multiple |
24 |
|
|
* threads. Iterators are <i>weakly consistent</i>, returning elements |
25 |
|
|
* reflecting the state of the set at some point at or since the |
26 |
|
|
* creation of the iterator. They do <em>not</em> throw {@link |
27 |
|
|
* ConcurrentModificationException}, and may procede concurrently with |
28 |
|
|
* other operations. |
29 |
|
|
* |
30 |
|
|
* <p>Beware that, unlike in most collections, the <tt>size</tt> |
31 |
dl |
1.4 |
* method is <em>not</em> a constant-time operation. Because of the |
32 |
dl |
1.1 |
* asynchronous nature of these sets, determining the current number |
33 |
dl |
1.4 |
* of elements requires a traversal of the elements. Additionally, the |
34 |
|
|
* bulk operations <tt>addAll</tt>, <tt>removeAll</tt>, |
35 |
|
|
* <<tt>retainAll</tt>, and tt>containsAll</tt> are <em>not</em> |
36 |
|
|
* guaranteed to be performed atomically. For example, an iterator |
37 |
|
|
* operating concurrently with an <tt>addAll</tt> operation might view |
38 |
|
|
* only some of the added elements. |
39 |
dl |
1.1 |
* |
40 |
|
|
* <p>This class and its iterators implement all of the |
41 |
|
|
* <em>optional</em> methods of the {@link Set} and {@link Iterator} |
42 |
|
|
* interfaces. Like most other concurrent collection implementations, |
43 |
|
|
* this class does not permit the use of <tt>null</tt> elements. |
44 |
dl |
1.3 |
* because <tt>null</tt> arguments and return values cannot be reliably |
45 |
dl |
1.1 |
* distinguished from the absence of elements. |
46 |
|
|
* |
47 |
|
|
* @author Doug Lea |
48 |
|
|
* @param <E> the type of elements maintained by this set |
49 |
|
|
*/ |
50 |
|
|
public class ConcurrentSkipListSet<E> |
51 |
|
|
extends AbstractSet<E> |
52 |
dl |
1.2 |
implements NavigableSet<E>, Cloneable, java.io.Serializable { |
53 |
dl |
1.1 |
|
54 |
|
|
private static final long serialVersionUID = -2479143111061671589L; |
55 |
|
|
|
56 |
|
|
/** |
57 |
|
|
* The underlying map. Uses Boolean.TRUE as value for each |
58 |
|
|
* element. Note that this class relies on default serialization, |
59 |
|
|
* which is a little wasteful in saving all of the useless value |
60 |
|
|
* fields of underlying map, but enables this field to be declared |
61 |
|
|
* final, which is necessary for thread safety. |
62 |
|
|
*/ |
63 |
|
|
private final ConcurrentSkipListMap<E,Object> m; |
64 |
|
|
|
65 |
|
|
/** |
66 |
|
|
* Constructs a new, empty set, sorted according to the elements' natural |
67 |
|
|
* order. |
68 |
|
|
*/ |
69 |
|
|
public ConcurrentSkipListSet() { |
70 |
|
|
m = new ConcurrentSkipListMap<E,Object>(); |
71 |
|
|
} |
72 |
|
|
|
73 |
|
|
/** |
74 |
|
|
* Constructs a new, empty set, sorted according to the specified |
75 |
|
|
* comparator. |
76 |
|
|
* |
77 |
|
|
* @param c the comparator that will be used to sort this set. A |
78 |
|
|
* <tt>null</tt> value indicates that the elements' <i>natural |
79 |
|
|
* ordering</i> should be used. |
80 |
|
|
*/ |
81 |
|
|
public ConcurrentSkipListSet(Comparator<? super E> c) { |
82 |
|
|
m = new ConcurrentSkipListMap<E,Object>(c); |
83 |
|
|
} |
84 |
|
|
|
85 |
|
|
/** |
86 |
|
|
* Constructs a new set containing the elements in the specified |
87 |
|
|
* collection, sorted according to the elements' <i>natural order</i>. |
88 |
|
|
* |
89 |
|
|
* @param c The elements that will comprise the new set. |
90 |
|
|
* |
91 |
|
|
* @throws ClassCastException if the elements in the specified |
92 |
|
|
* collection are not comparable, or are not mutually comparable. |
93 |
dl |
1.4 |
* @throws NullPointerException if the specified collection is |
94 |
|
|
* <tt>null</tt>. |
95 |
dl |
1.1 |
*/ |
96 |
|
|
public ConcurrentSkipListSet(Collection<? extends E> c) { |
97 |
|
|
m = new ConcurrentSkipListMap<E,Object>(); |
98 |
|
|
addAll(c); |
99 |
|
|
} |
100 |
|
|
|
101 |
|
|
/** |
102 |
|
|
* Constructs a new set containing the same elements as the specified |
103 |
|
|
* sorted set, sorted according to the same ordering. |
104 |
|
|
* |
105 |
|
|
* @param s sorted set whose elements will comprise the new set. |
106 |
dl |
1.4 |
* @throws NullPointerException if the specified sorted set is |
107 |
|
|
* <tt>null</tt>. |
108 |
dl |
1.1 |
*/ |
109 |
|
|
public ConcurrentSkipListSet(SortedSet<E> s) { |
110 |
|
|
m = new ConcurrentSkipListMap<E,Object>(s.comparator()); |
111 |
|
|
addAll(s); |
112 |
|
|
} |
113 |
|
|
|
114 |
|
|
/** |
115 |
|
|
* Returns a shallow copy of this set. (The elements themselves |
116 |
|
|
* are not cloned.) |
117 |
|
|
* |
118 |
|
|
* @return a shallow copy of this set. |
119 |
|
|
*/ |
120 |
|
|
public Object clone() { |
121 |
|
|
ConcurrentSkipListSet<E> clone = null; |
122 |
|
|
try { |
123 |
|
|
clone = (ConcurrentSkipListSet<E>) super.clone(); |
124 |
|
|
} catch (CloneNotSupportedException e) { |
125 |
|
|
throw new InternalError(); |
126 |
|
|
} |
127 |
|
|
|
128 |
|
|
clone.m.initialize(); |
129 |
|
|
clone.addAll(this); |
130 |
|
|
return clone; |
131 |
|
|
} |
132 |
|
|
|
133 |
|
|
/* ---------------- Set operations -------------- */ |
134 |
|
|
|
135 |
|
|
/** |
136 |
|
|
* Returns the number of elements in this set. If this set |
137 |
|
|
* contains more than <tt>Integer.MAX_VALUE</tt> elements, it |
138 |
|
|
* returns <tt>Integer.MAX_VALUE</tt>. |
139 |
|
|
* |
140 |
|
|
* <p>Beware that, unlike in most collections, this method is |
141 |
|
|
* <em>NOT</em> a constant-time operation. Because of the |
142 |
|
|
* asynchronous nature of these sets, determining the current |
143 |
|
|
* number of elements requires traversing them all to count them. |
144 |
|
|
* Additionally, it is possible for the size to change during |
145 |
|
|
* execution of this method, in which case the returned result |
146 |
|
|
* will be inaccurate. Thus, this method is typically not very |
147 |
|
|
* useful in concurrent applications. |
148 |
|
|
* |
149 |
|
|
* @return the number of elements in this set. |
150 |
|
|
*/ |
151 |
|
|
public int size() { |
152 |
|
|
return m.size(); |
153 |
|
|
} |
154 |
|
|
|
155 |
|
|
/** |
156 |
|
|
* Returns <tt>true</tt> if this set contains no elements. |
157 |
|
|
* @return <tt>true</tt> if this set contains no elements. |
158 |
|
|
*/ |
159 |
|
|
public boolean isEmpty() { |
160 |
|
|
return m.isEmpty(); |
161 |
|
|
} |
162 |
|
|
|
163 |
|
|
/** |
164 |
|
|
* Returns <tt>true</tt> if this set contains the specified element. |
165 |
|
|
* |
166 |
|
|
* @param o the object to be checked for containment in this set. |
167 |
|
|
* @return <tt>true</tt> if this set contains the specified element. |
168 |
|
|
* |
169 |
|
|
* @throws ClassCastException if the specified object cannot be compared |
170 |
|
|
* with the elements currently in the set. |
171 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
172 |
|
|
*/ |
173 |
|
|
public boolean contains(Object o) { |
174 |
|
|
return m.containsKey(o); |
175 |
|
|
} |
176 |
|
|
|
177 |
|
|
/** |
178 |
|
|
* Adds the specified element to this set if it is not already present. |
179 |
|
|
* |
180 |
|
|
* @param o element to be added to this set. |
181 |
|
|
* @return <tt>true</tt> if the set did not already contain the specified |
182 |
|
|
* element. |
183 |
|
|
* |
184 |
|
|
* @throws ClassCastException if the specified object cannot be compared |
185 |
|
|
* with the elements currently in the set. |
186 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
187 |
|
|
*/ |
188 |
|
|
public boolean add(E o) { |
189 |
|
|
return m.putIfAbsent(o, Boolean.TRUE) == null; |
190 |
|
|
} |
191 |
|
|
|
192 |
|
|
/** |
193 |
|
|
* Removes the specified element from this set if it is present. |
194 |
|
|
* |
195 |
|
|
* @param o object to be removed from this set, if present. |
196 |
|
|
* @return <tt>true</tt> if the set contained the specified element. |
197 |
|
|
* |
198 |
|
|
* @throws ClassCastException if the specified object cannot be compared |
199 |
|
|
* with the elements currently in the set. |
200 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
201 |
|
|
*/ |
202 |
|
|
public boolean remove(Object o) { |
203 |
|
|
return m.removep(o); |
204 |
|
|
} |
205 |
|
|
|
206 |
|
|
/** |
207 |
|
|
* Removes all of the elements from this set. |
208 |
|
|
*/ |
209 |
|
|
public void clear() { |
210 |
|
|
m.clear(); |
211 |
|
|
} |
212 |
|
|
|
213 |
|
|
/** |
214 |
|
|
* Returns an iterator over the elements in this set. The elements |
215 |
|
|
* are returned in ascending order. |
216 |
|
|
* |
217 |
|
|
* @return an iterator over the elements in this set. |
218 |
|
|
*/ |
219 |
|
|
public Iterator<E> iterator() { |
220 |
|
|
return m.keyIterator(); |
221 |
|
|
} |
222 |
dl |
1.4 |
|
223 |
|
|
/* ---------------- AbstractSet Overrides -------------- */ |
224 |
|
|
|
225 |
|
|
/** |
226 |
|
|
* Compares the specified object with this set for equality. Returns |
227 |
|
|
* <tt>true</tt> if the specified object is also a set, the two sets |
228 |
|
|
* have the same size, and every member of the specified set is |
229 |
|
|
* contained in this set (or equivalently, every member of this set is |
230 |
|
|
* contained in the specified set). This definition ensures that the |
231 |
|
|
* equals method works properly across different implementations of the |
232 |
|
|
* set interface. |
233 |
|
|
* |
234 |
|
|
* @param o Object to be compared for equality with this set. |
235 |
|
|
* @return <tt>true</tt> if the specified Object is equal to this set. |
236 |
|
|
*/ |
237 |
|
|
public boolean equals(Object o) { |
238 |
|
|
// Override AbstractSet version to avoid calling size() |
239 |
|
|
if (o == this) |
240 |
|
|
return true; |
241 |
|
|
if (!(o instanceof Set)) |
242 |
|
|
return false; |
243 |
|
|
Collection c = (Collection) o; |
244 |
|
|
try { |
245 |
|
|
return containsAll(c) && c.containsAll(this); |
246 |
|
|
} catch(ClassCastException unused) { |
247 |
|
|
return false; |
248 |
|
|
} catch(NullPointerException unused) { |
249 |
|
|
return false; |
250 |
|
|
} |
251 |
|
|
} |
252 |
|
|
|
253 |
|
|
/** |
254 |
|
|
* Removes from this set all of its elements that are contained in |
255 |
|
|
* the specified collection. If the specified collection is also |
256 |
|
|
* a set, this operation effectively modifies this set so that its |
257 |
|
|
* value is the <i>asymmetric set difference</i> of the two sets. |
258 |
|
|
* |
259 |
|
|
* @param c collection that defines which elements will be removed from |
260 |
|
|
* this set. |
261 |
|
|
* @return <tt>true</tt> if this set changed as a result of the call. |
262 |
|
|
* |
263 |
|
|
* @throws ClassCastException if the types of one or more elements in this |
264 |
|
|
* set are incompatible with the specified collection |
265 |
|
|
* @throws NullPointerException if the specified collection, or any |
266 |
|
|
* of its elements are <tt>null</tt>. |
267 |
|
|
*/ |
268 |
|
|
public boolean removeAll(Collection<?> c) { |
269 |
|
|
// Override AbstractSet version to avoid unnecessary call to size() |
270 |
|
|
boolean modified = false; |
271 |
|
|
for (Iterator<?> i = c.iterator(); i.hasNext(); ) |
272 |
|
|
if (remove(i.next())) |
273 |
|
|
modified = true; |
274 |
|
|
return modified; |
275 |
|
|
} |
276 |
dl |
1.1 |
|
277 |
|
|
/* ---------------- Relational operations -------------- */ |
278 |
|
|
|
279 |
|
|
/** |
280 |
|
|
* Returns an element greater than or equal to the given element, or |
281 |
dl |
1.3 |
* <tt>null</tt> if there is no such element. |
282 |
dl |
1.1 |
* |
283 |
|
|
* @param o the value to match |
284 |
dl |
1.4 |
* @return an element greater than or equal to given element, or |
285 |
|
|
* <tt>null</tt> if there is no such element. |
286 |
dl |
1.1 |
* @throws ClassCastException if o cannot be compared with the elements |
287 |
|
|
* currently in the set. |
288 |
|
|
* @throws NullPointerException if o is <tt>null</tt> |
289 |
|
|
*/ |
290 |
|
|
public E ceiling(E o) { |
291 |
|
|
return m.ceilingKey(o); |
292 |
|
|
} |
293 |
|
|
|
294 |
|
|
/** |
295 |
dl |
1.4 |
* Returns an element strictly less than the given element, or |
296 |
|
|
* <tt>null</tt> if there is no such element. |
297 |
dl |
1.1 |
* |
298 |
|
|
* @param o the value to match |
299 |
|
|
* @return the greatest element less than the given element, or |
300 |
dl |
1.3 |
* <tt>null</tt> if there is no such element. |
301 |
dl |
1.1 |
* @throws ClassCastException if o cannot be compared with the elements |
302 |
|
|
* currently in the set. |
303 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
304 |
|
|
*/ |
305 |
|
|
public E lower(E o) { |
306 |
|
|
return m.lowerKey(o); |
307 |
|
|
} |
308 |
|
|
|
309 |
|
|
/** |
310 |
dl |
1.4 |
* Returns an element less than or equal to the given element, or |
311 |
|
|
* <tt>null</tt> if there is no such element. |
312 |
dl |
1.1 |
* |
313 |
|
|
* @param o the value to match |
314 |
|
|
* @return the greatest element less than or equal to given |
315 |
dl |
1.3 |
* element, or <tt>null</tt> if there is no such element. |
316 |
dl |
1.1 |
* @throws ClassCastException if o cannot be compared with the elements |
317 |
|
|
* currently in the set. |
318 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
319 |
|
|
*/ |
320 |
|
|
public E floor(E o) { |
321 |
|
|
return m.floorKey(o); |
322 |
|
|
} |
323 |
|
|
|
324 |
|
|
/** |
325 |
dl |
1.4 |
* Returns an element strictly greater than the given element, or |
326 |
|
|
* <tt>null</tt> if there is no such element. |
327 |
dl |
1.1 |
* |
328 |
|
|
* @param o the value to match |
329 |
|
|
* @return the least element greater than the given element, or |
330 |
dl |
1.3 |
* <tt>null</tt> if there is no such element. |
331 |
dl |
1.1 |
* @throws ClassCastException if o cannot be compared with the elements |
332 |
|
|
* currently in the set. |
333 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
334 |
|
|
*/ |
335 |
|
|
public E higher(E o) { |
336 |
|
|
return m.higherKey(o); |
337 |
|
|
} |
338 |
|
|
|
339 |
dl |
1.2 |
/** |
340 |
|
|
* Retrieves and removes the first (lowest) element. |
341 |
|
|
* |
342 |
|
|
* @return the least element, or <tt>null</tt> if empty. |
343 |
|
|
*/ |
344 |
|
|
public E pollFirst() { |
345 |
|
|
return m.removeFirstKey(); |
346 |
|
|
} |
347 |
|
|
|
348 |
|
|
/** |
349 |
|
|
* Retrieves and removes the last (highest) element. |
350 |
|
|
* |
351 |
|
|
* @return the last element, or <tt>null</tt> if empty. |
352 |
|
|
*/ |
353 |
|
|
public E pollLast() { |
354 |
|
|
return m.removeLastKey(); |
355 |
|
|
} |
356 |
|
|
|
357 |
|
|
|
358 |
dl |
1.1 |
/* ---------------- SortedSet operations -------------- */ |
359 |
|
|
|
360 |
|
|
|
361 |
|
|
/** |
362 |
|
|
* Returns the comparator used to order this set, or <tt>null</tt> |
363 |
|
|
* if this set uses its elements natural ordering. |
364 |
|
|
* |
365 |
|
|
* @return the comparator used to order this set, or <tt>null</tt> |
366 |
|
|
* if this set uses its elements natural ordering. |
367 |
|
|
*/ |
368 |
|
|
public Comparator<? super E> comparator() { |
369 |
|
|
return m.comparator(); |
370 |
|
|
} |
371 |
|
|
|
372 |
|
|
/** |
373 |
|
|
* Returns the first (lowest) element currently in this set. |
374 |
|
|
* |
375 |
|
|
* @return the first (lowest) element currently in this set. |
376 |
|
|
* @throws NoSuchElementException sorted set is empty. |
377 |
|
|
*/ |
378 |
|
|
public E first() { |
379 |
|
|
return m.firstKey(); |
380 |
|
|
} |
381 |
|
|
|
382 |
|
|
/** |
383 |
|
|
* Returns the last (highest) element currently in this set. |
384 |
|
|
* |
385 |
|
|
* @return the last (highest) element currently in this set. |
386 |
|
|
* @throws NoSuchElementException sorted set is empty. |
387 |
|
|
*/ |
388 |
|
|
public E last() { |
389 |
|
|
return m.lastKey(); |
390 |
|
|
} |
391 |
|
|
|
392 |
dl |
1.4 |
|
393 |
|
|
|
394 |
dl |
1.1 |
/** |
395 |
|
|
* Returns a view of the portion of this set whose elements range from |
396 |
|
|
* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive. (If |
397 |
|
|
* <tt>fromElement</tt> and <tt>toElement</tt> are equal, the returned |
398 |
|
|
* sorted set is empty.) The returned sorted set is backed by this set, |
399 |
|
|
* so changes in the returned sorted set are reflected in this set, and |
400 |
|
|
* vice-versa. |
401 |
|
|
* @param fromElement low endpoint (inclusive) of the subSet. |
402 |
|
|
* @param toElement high endpoint (exclusive) of the subSet. |
403 |
|
|
* @return a view of the portion of this set whose elements range from |
404 |
|
|
* <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, |
405 |
|
|
* exclusive. |
406 |
|
|
* @throws ClassCastException if <tt>fromElement</tt> and |
407 |
|
|
* <tt>toElement</tt> cannot be compared to one another using |
408 |
|
|
* this set's comparator (or, if the set has no comparator, |
409 |
|
|
* using natural ordering). |
410 |
|
|
* @throws IllegalArgumentException if <tt>fromElement</tt> is |
411 |
|
|
* greater than <tt>toElement</tt>. |
412 |
|
|
* @throws NullPointerException if <tt>fromElement</tt> or |
413 |
|
|
* <tt>toElement</tt> is <tt>null</tt>. |
414 |
|
|
*/ |
415 |
dl |
1.2 |
public NavigableSet<E> subSet(E fromElement, E toElement) { |
416 |
dl |
1.1 |
return new ConcurrentSkipListSubSet<E>(m, fromElement, toElement); |
417 |
|
|
} |
418 |
|
|
|
419 |
|
|
/** |
420 |
|
|
* Returns a view of the portion of this set whose elements are strictly |
421 |
|
|
* less than <tt>toElement</tt>. The returned sorted set is backed by |
422 |
|
|
* this set, so changes in the returned sorted set are reflected in this |
423 |
|
|
* set, and vice-versa. |
424 |
|
|
* @param toElement high endpoint (exclusive) of the headSet. |
425 |
|
|
* @return a view of the portion of this set whose elements are strictly |
426 |
|
|
* less than toElement. |
427 |
|
|
* @throws ClassCastException if <tt>toElement</tt> is not compatible |
428 |
|
|
* with this set's comparator (or, if the set has no comparator, |
429 |
|
|
* if <tt>toElement</tt> does not implement <tt>Comparable</tt>). |
430 |
|
|
* @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>. |
431 |
|
|
*/ |
432 |
dl |
1.2 |
public NavigableSet<E> headSet(E toElement) { |
433 |
dl |
1.1 |
return new ConcurrentSkipListSubSet<E>(m, null, toElement); |
434 |
|
|
} |
435 |
|
|
|
436 |
|
|
|
437 |
|
|
/** |
438 |
|
|
* Returns a view of the portion of this set whose elements are |
439 |
|
|
* greater than or equal to <tt>fromElement</tt>. The returned |
440 |
|
|
* sorted set is backed by this set, so changes in the returned |
441 |
|
|
* sorted set are reflected in this set, and vice-versa. |
442 |
|
|
* @param fromElement low endpoint (inclusive) of the tailSet. |
443 |
|
|
* @return a view of the portion of this set whose elements are |
444 |
|
|
* greater than or equal to <tt>fromElement</tt>. |
445 |
|
|
* @throws ClassCastException if <tt>fromElement</tt> is not |
446 |
|
|
* compatible with this set's comparator (or, if the set has no |
447 |
|
|
* comparator, if <tt>fromElement</tt> does not implement |
448 |
|
|
* <tt>Comparable</tt>). |
449 |
|
|
* @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>. |
450 |
|
|
*/ |
451 |
dl |
1.2 |
public NavigableSet<E> tailSet(E fromElement) { |
452 |
dl |
1.1 |
return new ConcurrentSkipListSubSet<E>(m, fromElement, null); |
453 |
|
|
} |
454 |
dl |
1.2 |
|
455 |
|
|
/** |
456 |
|
|
* Subsets returned by {@link ConcurrentSkipListSet} subset operations |
457 |
|
|
* represent a subrange of elements of their underlying |
458 |
|
|
* sets. Instances of this class support all methods of their |
459 |
|
|
* underlying sets, differing in that elements outside their range are |
460 |
|
|
* ignored, and attempts to add elements outside their ranges result |
461 |
|
|
* in {@link IllegalArgumentException}. Instances of this class are |
462 |
|
|
* constructed only using the <tt>subSet</tt>, <tt>headSet</tt>, and |
463 |
|
|
* <tt>tailSet</tt> methods of their underlying sets. |
464 |
|
|
* |
465 |
|
|
*/ |
466 |
|
|
static class ConcurrentSkipListSubSet<E> |
467 |
|
|
extends AbstractSet<E> |
468 |
|
|
implements NavigableSet<E>, java.io.Serializable { |
469 |
|
|
|
470 |
|
|
private static final long serialVersionUID = -7647078645896651609L; |
471 |
|
|
|
472 |
|
|
/** The underlying submap */ |
473 |
|
|
private final ConcurrentSkipListMap.ConcurrentSkipListSubMap<E,Object> s; |
474 |
|
|
|
475 |
|
|
/** |
476 |
|
|
* Creates a new submap. |
477 |
dl |
1.3 |
* @param fromElement inclusive least value, or <tt>null</tt> if from start |
478 |
|
|
* @param toElement exclusive upper bound or <tt>null</tt> if to end |
479 |
dl |
1.2 |
* @throws IllegalArgumentException if fromElement and toElement |
480 |
|
|
* nonnull and fromElement greater than toElement |
481 |
|
|
*/ |
482 |
|
|
ConcurrentSkipListSubSet(ConcurrentSkipListMap<E,Object> map, |
483 |
|
|
E fromElement, E toElement) { |
484 |
|
|
s = new ConcurrentSkipListMap.ConcurrentSkipListSubMap<E,Object>(map, fromElement, |
485 |
|
|
toElement); |
486 |
|
|
} |
487 |
|
|
|
488 |
|
|
/** |
489 |
|
|
* Returns the number of elements in this set. If this set |
490 |
|
|
* contains more than <tt>Integer.MAX_VALUE</tt> elements, it |
491 |
|
|
* returns <tt>Integer.MAX_VALUE</tt>. |
492 |
|
|
* |
493 |
|
|
* <p>Beware that, unlike in most collections, this method is |
494 |
|
|
* <em>NOT</em> a constant-time operation. Because of the |
495 |
|
|
* asynchronous nature of these sets, determining the current |
496 |
|
|
* number of elements requires traversing them all to count them. |
497 |
|
|
* Additionally, it is possible for the size to change during |
498 |
|
|
* execution of this method, in which case the returned result |
499 |
|
|
* will be inaccurate. Thus, this method is typically not very |
500 |
|
|
* useful in concurrent applications. |
501 |
|
|
* |
502 |
|
|
* @return the number of elements in this set. |
503 |
|
|
*/ |
504 |
|
|
public int size() { |
505 |
|
|
return s.size(); |
506 |
|
|
} |
507 |
|
|
|
508 |
|
|
/** |
509 |
|
|
* Returns <tt>true</tt> if this set contains no elements. |
510 |
|
|
* @return <tt>true</tt> if this set contains no elements. |
511 |
|
|
*/ |
512 |
|
|
public boolean isEmpty() { |
513 |
|
|
return s.isEmpty(); |
514 |
|
|
} |
515 |
|
|
|
516 |
|
|
/** |
517 |
|
|
* Returns <tt>true</tt> if this set contains the specified |
518 |
|
|
* element. |
519 |
|
|
* |
520 |
|
|
* @param o the object to be checked for containment in this |
521 |
|
|
* set. |
522 |
|
|
* @return <tt>true</tt> if this set contains the specified |
523 |
|
|
* element. |
524 |
|
|
* |
525 |
|
|
* @throws ClassCastException if the specified object cannot |
526 |
|
|
* be compared with the elements currently in the set. |
527 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
528 |
|
|
*/ |
529 |
|
|
public boolean contains(Object o) { |
530 |
|
|
return s.containsKey(o); |
531 |
|
|
} |
532 |
|
|
|
533 |
|
|
|
534 |
|
|
/** |
535 |
|
|
* Adds the specified element to this set if it is not already |
536 |
|
|
* present. |
537 |
|
|
* |
538 |
|
|
* @param o element to be added to this set. |
539 |
|
|
* @return <tt>true</tt> if the set did not already contain |
540 |
|
|
* the specified element. |
541 |
|
|
* |
542 |
|
|
* @throws ClassCastException if the specified object cannot |
543 |
|
|
* be compared with the elements currently in the set. |
544 |
|
|
* @throws IllegalArgumentException if o is outside the range |
545 |
|
|
* of this subset. |
546 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
547 |
|
|
*/ |
548 |
|
|
public boolean add(E o) { |
549 |
|
|
return s.put(o, Boolean.TRUE) == null; |
550 |
|
|
} |
551 |
|
|
|
552 |
|
|
/** |
553 |
|
|
* Removes the specified element from this set if it is |
554 |
|
|
* present. |
555 |
|
|
* |
556 |
|
|
* @param o object to be removed from this set, if present. |
557 |
|
|
* @return <tt>true</tt> if the set contained the specified element. |
558 |
|
|
* |
559 |
|
|
* @throws ClassCastException if the specified object cannot |
560 |
|
|
* be compared with the elements currently in the set. |
561 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
562 |
|
|
*/ |
563 |
|
|
public boolean remove(Object o) { |
564 |
|
|
return s.remove(o) != null; |
565 |
|
|
} |
566 |
|
|
|
567 |
|
|
/** |
568 |
|
|
* Removes all of the elements from this set. |
569 |
|
|
*/ |
570 |
|
|
public void clear() { |
571 |
|
|
s.clear(); |
572 |
|
|
} |
573 |
|
|
|
574 |
|
|
/** |
575 |
|
|
* Returns an iterator over the elements in this set. The elements |
576 |
|
|
* are returned in ascending order. |
577 |
|
|
* |
578 |
|
|
* @return an iterator over the elements in this set. |
579 |
|
|
*/ |
580 |
|
|
public Iterator<E> iterator() { |
581 |
|
|
return s.keySet().iterator(); |
582 |
|
|
} |
583 |
|
|
|
584 |
|
|
/** |
585 |
|
|
* Returns an element greater than or equal to the given |
586 |
dl |
1.3 |
* element, or <tt>null</tt> if there is no such element. |
587 |
dl |
1.2 |
* |
588 |
|
|
* @param o the value to match |
589 |
dl |
1.3 |
* @return an element greater than or equal to given element, or <tt>null</tt> |
590 |
dl |
1.2 |
* if there is no such element. |
591 |
|
|
* @throws ClassCastException if o cannot be compared with the |
592 |
|
|
* elements currently in the set. |
593 |
|
|
* @throws NullPointerException if o is <tt>null</tt> |
594 |
|
|
*/ |
595 |
|
|
public E ceiling(E o) { |
596 |
|
|
E key = o; |
597 |
|
|
E least = s.getLeast(); |
598 |
|
|
if (least != null && s.getMap().compare(o, least) < 0) |
599 |
|
|
key = least; |
600 |
|
|
E k = s.getMap().ceilingKey(key); |
601 |
|
|
return (k != null && s.inHalfOpenRange(k))? k : null; |
602 |
|
|
} |
603 |
|
|
|
604 |
|
|
/** |
605 |
dl |
1.3 |
* Returns an element strictly less than the given element, or <tt>null</tt> if |
606 |
dl |
1.2 |
* there is no such element. |
607 |
|
|
* |
608 |
|
|
* @param o the value to match |
609 |
|
|
* @return the greatest element less than the given element, or |
610 |
dl |
1.3 |
* <tt>null</tt> if there is no such element. |
611 |
dl |
1.2 |
* @throws ClassCastException if o cannot be compared with the |
612 |
|
|
* elements currently in the set. |
613 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
614 |
|
|
*/ |
615 |
|
|
public E lower(E o) { |
616 |
|
|
E k = s.getMap().lowerKey(o); |
617 |
|
|
return (k != null && s.inHalfOpenRange(k))? k : null; |
618 |
|
|
} |
619 |
|
|
|
620 |
|
|
/** |
621 |
dl |
1.3 |
* Returns an element less than or equal to the given element, or <tt>null</tt> |
622 |
dl |
1.2 |
* if there is no such element. |
623 |
|
|
* |
624 |
|
|
* @param o the value to match |
625 |
|
|
* @return the greatest element less than or equal to given |
626 |
dl |
1.3 |
* element, or <tt>null</tt> if there is no such element. |
627 |
dl |
1.2 |
* @throws ClassCastException if o cannot be compared with the |
628 |
|
|
* elements currently in the set. |
629 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
630 |
|
|
*/ |
631 |
|
|
public E floor(E o) { |
632 |
|
|
E k = s.getMap().floorKey(o); |
633 |
|
|
return (k != null && s.inHalfOpenRange(k))? k : null; |
634 |
|
|
} |
635 |
|
|
|
636 |
|
|
/** |
637 |
dl |
1.3 |
* Returns an element strictly greater than the given element, or <tt>null</tt> |
638 |
dl |
1.2 |
* if there is no such element. |
639 |
|
|
* |
640 |
|
|
* @param o the value to match |
641 |
|
|
* @return the least element greater than the given element, or |
642 |
dl |
1.3 |
* <tt>null</tt> if there is no such element. |
643 |
dl |
1.2 |
* @throws ClassCastException if o cannot be compared with the |
644 |
|
|
* elements currently in the set. |
645 |
|
|
* @throws NullPointerException if o is <tt>null</tt>. |
646 |
|
|
*/ |
647 |
|
|
public E higher(E o) { |
648 |
|
|
E k; |
649 |
|
|
E least = s.getLeast(); |
650 |
|
|
if (least != null && s.getMap().compare(o, least) < 0) |
651 |
|
|
k = s.getMap().ceilingKey(least); |
652 |
|
|
else |
653 |
|
|
k = s.getMap().higherKey(o); |
654 |
|
|
return (k != null && s.inHalfOpenRange(k))? k : null; |
655 |
|
|
} |
656 |
|
|
|
657 |
|
|
/** |
658 |
|
|
* Retrieves and removes the first (lowest) element. |
659 |
|
|
* |
660 |
|
|
* @return the first element, or <tt>null</tt> if empty. |
661 |
|
|
*/ |
662 |
|
|
public E pollFirst() { |
663 |
|
|
for (;;) { |
664 |
|
|
E k = s.lowestKey(); |
665 |
|
|
if (k == null) |
666 |
|
|
return null; |
667 |
|
|
if (remove(k)) |
668 |
|
|
return k; |
669 |
|
|
} |
670 |
|
|
} |
671 |
|
|
|
672 |
|
|
/** |
673 |
|
|
* Retrieves and removes the last (highest) element. |
674 |
|
|
* |
675 |
|
|
* @return the last element, or <tt>null</tt> if empty. |
676 |
|
|
*/ |
677 |
|
|
public E pollLast() { |
678 |
|
|
for (;;) { |
679 |
|
|
E k = s.highestKey(); |
680 |
|
|
if (k == null) |
681 |
|
|
return null; |
682 |
|
|
if (remove(k)) |
683 |
|
|
return k; |
684 |
|
|
} |
685 |
|
|
} |
686 |
|
|
|
687 |
|
|
/** |
688 |
|
|
* Returns the comparator used to order this set, or <tt>null</tt> |
689 |
|
|
* if this set uses its elements natural ordering. |
690 |
|
|
* |
691 |
|
|
* @return the comparator used to order this set, or <tt>null</tt> |
692 |
|
|
* if this set uses its elements natural ordering. |
693 |
|
|
*/ |
694 |
|
|
public Comparator<? super E> comparator() { |
695 |
|
|
return s.comparator(); |
696 |
|
|
} |
697 |
|
|
|
698 |
|
|
/** |
699 |
|
|
* Returns the first (lowest) element currently in this set. |
700 |
|
|
* |
701 |
|
|
* @return the first (lowest) element currently in this set. |
702 |
|
|
* @throws NoSuchElementException sorted set is empty. |
703 |
|
|
*/ |
704 |
|
|
public E first() { |
705 |
|
|
return s.firstKey(); |
706 |
|
|
} |
707 |
|
|
|
708 |
|
|
/** |
709 |
|
|
* Returns the last (highest) element currently in this set. |
710 |
|
|
* |
711 |
|
|
* @return the last (highest) element currently in this set. |
712 |
|
|
* @throws NoSuchElementException sorted set is empty. |
713 |
|
|
*/ |
714 |
|
|
public E last() { |
715 |
|
|
return s.lastKey(); |
716 |
|
|
} |
717 |
|
|
|
718 |
|
|
/** |
719 |
|
|
* Returns a view of the portion of this set whose elements |
720 |
|
|
* range from <tt>fromElement</tt>, inclusive, to |
721 |
|
|
* <tt>toElement</tt>, exclusive. (If <tt>fromElement</tt> |
722 |
|
|
* and <tt>toElement</tt> are equal, the returned sorted set |
723 |
|
|
* is empty.) The returned sorted set is backed by this set, |
724 |
|
|
* so changes in the returned sorted set are reflected in this |
725 |
|
|
* set, and vice-versa. |
726 |
|
|
* @param fromElement low endpoint (inclusive) of the subSet. |
727 |
|
|
* @param toElement high endpoint (exclusive) of the subSet. |
728 |
|
|
* @return a view of the portion of this set whose elements |
729 |
|
|
* range from <tt>fromElement</tt>, inclusive, to |
730 |
|
|
* <tt>toElement</tt>, exclusive. |
731 |
|
|
* @throws ClassCastException if <tt>fromElement</tt> and |
732 |
|
|
* <tt>toElement</tt> cannot be compared to one another using |
733 |
|
|
* this set's comparator (or, if the set has no comparator, |
734 |
|
|
* using natural ordering). |
735 |
|
|
* @throws IllegalArgumentException if <tt>fromElement</tt> is |
736 |
|
|
* greater than <tt>toElement</tt> or either key is outside |
737 |
|
|
* the range of this set. |
738 |
|
|
* @throws NullPointerException if <tt>fromElement</tt> or |
739 |
|
|
* <tt>toElement</tt> is <tt>null</tt>. |
740 |
|
|
*/ |
741 |
|
|
public NavigableSet<E> subSet(E fromElement, |
742 |
|
|
E toElement) { |
743 |
|
|
if (!s.inOpenRange(fromElement) || !s.inOpenRange(toElement)) |
744 |
|
|
throw new IllegalArgumentException("element out of range"); |
745 |
|
|
return new ConcurrentSkipListSubSet<E>(s.getMap(), |
746 |
|
|
fromElement, toElement); |
747 |
|
|
} |
748 |
|
|
|
749 |
|
|
/** |
750 |
|
|
* Returns a view of the portion of this set whose elements are |
751 |
|
|
* strictly less than <tt>toElement</tt>. The returned sorted set |
752 |
|
|
* is backed by this set, so changes in the returned sorted set |
753 |
|
|
* are reflected in this set, and vice-versa. |
754 |
|
|
* @param toElement high endpoint (exclusive) of the headSet. |
755 |
|
|
* @return a view of the portion of this set whose elements |
756 |
|
|
* are strictly less than toElement. |
757 |
|
|
* @throws ClassCastException if <tt>toElement</tt> is not |
758 |
|
|
* compatible with this set's comparator (or, if the set has |
759 |
|
|
* no comparator, if <tt>toElement</tt> does not implement |
760 |
|
|
* <tt>Comparable</tt>). |
761 |
|
|
* @throws IllegalArgumentException if <tt>toElement</tt> is |
762 |
|
|
* outside the range of this set. |
763 |
|
|
* @throws NullPointerException if <tt>toElement</tt> is |
764 |
|
|
* <tt>null</tt>. |
765 |
|
|
*/ |
766 |
|
|
public NavigableSet<E> headSet(E toElement) { |
767 |
|
|
E least = s.getLeast(); |
768 |
|
|
if (!s.inOpenRange(toElement)) |
769 |
|
|
throw new IllegalArgumentException("element out of range"); |
770 |
|
|
return new ConcurrentSkipListSubSet<E>(s.getMap(), |
771 |
|
|
least, toElement); |
772 |
|
|
} |
773 |
|
|
|
774 |
|
|
/** |
775 |
|
|
* Returns a view of the portion of this set whose elements |
776 |
|
|
* are greater than or equal to <tt>fromElement</tt>. The |
777 |
|
|
* returned sorted set is backed by this set, so changes in |
778 |
|
|
* the returned sorted set are reflected in this set, and |
779 |
|
|
* vice-versa. |
780 |
|
|
* @param fromElement low endpoint (inclusive) of the tailSet. |
781 |
|
|
* @return a view of the portion of this set whose elements |
782 |
|
|
* are greater than or equal to <tt>fromElement</tt>. |
783 |
|
|
* @throws ClassCastException if <tt>fromElement</tt> is not |
784 |
|
|
* compatible with this set's comparator (or, if the set has |
785 |
|
|
* no comparator, if <tt>fromElement</tt> does not implement |
786 |
|
|
* <tt>Comparable</tt>). |
787 |
|
|
* @throws IllegalArgumentException if <tt>fromElement</tt> is |
788 |
|
|
* outside the range of this set. |
789 |
|
|
* @throws NullPointerException if <tt>fromElement</tt> is |
790 |
|
|
* <tt>null</tt>. |
791 |
|
|
*/ |
792 |
|
|
public NavigableSet<E> tailSet(E fromElement) { |
793 |
|
|
E fence = s.getFence(); |
794 |
|
|
if (!s.inOpenRange(fromElement)) |
795 |
|
|
throw new IllegalArgumentException("element out of range"); |
796 |
|
|
return new ConcurrentSkipListSubSet<E>(s.getMap(), |
797 |
|
|
fromElement, fence); |
798 |
|
|
} |
799 |
|
|
} |
800 |
dl |
1.1 |
} |