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Comparing jsr166/src/jsr166x/ConcurrentSkipListSet.java (file contents):
Revision 1.3 by dl, Tue Sep 7 11:37:57 2004 UTC vs.
Revision 1.18 by jsr166, Wed Jan 16 00:53:17 2013 UTC

# Line 1 | Line 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
4 > * http://creativecommons.org/publicdomain/zero/1.0/
5   */
6  
7 < package jsr166x;
7 > package jsr166x;
8  
9   import java.util.*;
10   import java.util.concurrent.*;
# Line 15 | Line 15 | import java.util.concurrent.*;
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>
18 > * used.
19   *
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>
20 > * <p>This implementation provides expected average <i>log(n)</i> time
21 > * cost for the {@code contains}, {@code add}, and {@code remove}
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
27 > * ConcurrentModificationException}, and may proceed concurrently with
28   * other operations.
29   *
30 < * <p>Beware that, unlike in most collections, the <tt>size</tt>
31 < * method is <em>NOT</em> a constant-time operation. Because of the
30 > * <p>Beware that, unlike in most collections, the {@code size}
31 > * method is <em>not</em> a constant-time operation. Because of the
32   * asynchronous nature of these sets, determining the current number
33 < * of elements requires a traversal of the elements.
33 > * of elements requires a traversal of the elements. Additionally, the
34 > * bulk operations {@code addAll}, {@code removeAll},
35 > * {@code retainAll}, and {@code containsAll} are <em>not</em>
36 > * guaranteed to be performed atomically. For example, an iterator
37 > * operating concurrently with an {@code addAll} operation might view
38 > * only some of the added elements.
39   *
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 < * because <tt>null</tt> arguments and return values cannot be reliably
43 > * this class does not permit the use of {@code null} elements.
44 > * because {@code null} arguments and return values cannot be reliably
45   * distinguished from the absence of elements.
46   *
47   * @author Doug Lea
# Line 55 | Line 60 | public class ConcurrentSkipListSet<E>
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;
63 >    private final ConcurrentSkipListMap<E,Object> m;
64  
65      /**
66       * Constructs a new, empty set, sorted according to the elements' natural
67 <     * order.
67 >     * order.
68       */
69      public ConcurrentSkipListSet() {
70          m = new ConcurrentSkipListMap<E,Object>();
# Line 67 | Line 72 | public class ConcurrentSkipListSet<E>
72  
73      /**
74       * Constructs a new, empty set, sorted according to the specified
75 <     * comparator.  
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
78 >     *        {@code null} value indicates that the elements' <i>natural
79       *        ordering</i> should be used.
80       */
81      public ConcurrentSkipListSet(Comparator<? super E> c) {
# Line 81 | Line 86 | public class ConcurrentSkipListSet<E>
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.
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 <     * @throws NullPointerException if the specified collection is <tt>null</tt>.
92 >     * collection are not comparable, or are not mutually comparable
93 >     * @throws NullPointerException if the specified collection is
94 >     * {@code null}
95       */
96      public ConcurrentSkipListSet(Collection<? extends E> c) {
97          m = new ConcurrentSkipListMap<E,Object>();
# Line 96 | Line 102 | public class ConcurrentSkipListSet<E>
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 <     * @throws NullPointerException if the specified sorted set is <tt>null</tt>.
105 >     * @param s sorted set whose elements will comprise the new set
106 >     * @throws NullPointerException if the specified sorted set is
107 >     * {@code null}
108       */
109      public ConcurrentSkipListSet(SortedSet<E> s) {
110          m = new ConcurrentSkipListMap<E,Object>(s.comparator());
# Line 108 | Line 115 | public class ConcurrentSkipListSet<E>
115       * Returns a shallow copy of this set. (The elements themselves
116       * are not cloned.)
117       *
118 <     * @return a shallow copy of this set.
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 <        }
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);
# Line 127 | Line 134 | public class ConcurrentSkipListSet<E>
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>.
137 >     * contains more than {@code Integer.MAX_VALUE} elements, it
138 >     * returns {@code Integer.MAX_VALUE}.
139       *
140       * <p>Beware that, unlike in most collections, this method is
141       * <em>NOT</em> a constant-time operation. Because of the
# Line 139 | Line 146 | public class ConcurrentSkipListSet<E>
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.
149 >     * @return  the number of elements in this set
150       */
151      public int size() {
152 <        return m.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.
156 >     * Returns {@code true} if this set contains no elements.
157 >     * @return {@code true} if this set contains no elements
158       */
159      public boolean isEmpty() {
160 <        return m.isEmpty();
160 >        return m.isEmpty();
161      }
162  
163      /**
164 <     * Returns <tt>true</tt> if this set contains the specified element.
164 >     * Returns {@code true} 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.
166 >     * @param o the object to be checked for containment in this set
167 >     * @return {@code true} 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>.
170 >     *            with the elements currently in the set
171 >     * @throws NullPointerException if o is {@code null}
172       */
173      public boolean contains(Object o) {
174 <        return m.containsKey(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.
180 >     * @param o element to be added to this set
181 >     * @return {@code true} 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>.
185 >     *            with the elements currently in the set
186 >     * @throws NullPointerException if o is {@code null}
187       */
188      public boolean add(E o) {
189 <        return m.putIfAbsent(o, Boolean.TRUE) == null;
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.
195 >     * @param o object to be removed from this set, if present
196 >     * @return {@code true} 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>.
199 >     *            with the elements currently in the set
200 >     * @throws NullPointerException if o is {@code null}
201       */
202      public boolean remove(Object o) {
203 <        return m.removep(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();
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.
217 >     * @return an iterator over the elements in this set
218       */
219      public Iterator<E> iterator() {
220 <        return m.keyIterator();
220 >        return m.keyIterator();
221 >    }
222 >
223 >    /**
224 >     * Returns an iterator over the elements in this set.  The elements
225 >     * are returned in descending order.
226 >     *
227 >     * @return an iterator over the elements in this set
228 >     */
229 >    public Iterator<E> descendingIterator() {
230 >        return m.descendingKeyIterator();
231 >    }
232 >
233 >    /* ---------------- AbstractSet Overrides -------------- */
234 >
235 >    /**
236 >     * Compares the specified object with this set for equality.  Returns
237 >     * {@code true} if the specified object is also a set, the two sets
238 >     * have the same size, and every member of the specified set is
239 >     * contained in this set (or equivalently, every member of this set is
240 >     * contained in the specified set).  This definition ensures that the
241 >     * equals method works properly across different implementations of the
242 >     * set interface.
243 >     *
244 >     * @param o Object to be compared for equality with this set
245 >     * @return {@code true} if the specified Object is equal to this set
246 >     */
247 >    public boolean equals(Object o) {
248 >        // Override AbstractSet version to avoid calling size()
249 >        if (o == this)
250 >            return true;
251 >        if (!(o instanceof Set))
252 >            return false;
253 >        Collection c = (Collection) o;
254 >        try {
255 >            return containsAll(c) && c.containsAll(this);
256 >        } catch (ClassCastException unused) {
257 >            return false;
258 >        } catch (NullPointerException unused) {
259 >            return false;
260 >        }
261 >    }
262 >
263 >    /**
264 >     * Removes from this set all of its elements that are contained in
265 >     * the specified collection.  If the specified collection is also
266 >     * a set, this operation effectively modifies this set so that its
267 >     * value is the <i>asymmetric set difference</i> of the two sets.
268 >     *
269 >     * @param  c collection that defines which elements will be removed from
270 >     *           this set
271 >     * @return {@code true} if this set changed as a result of the call
272 >     *
273 >     * @throws ClassCastException if the types of one or more elements in this
274 >     *            set are incompatible with the specified collection
275 >     * @throws NullPointerException if the specified collection, or any
276 >     * of its elements are {@code null}
277 >     */
278 >    public boolean removeAll(Collection<?> c) {
279 >        // Override AbstractSet version to avoid unnecessary call to size()
280 >        boolean modified = false;
281 >        for (Iterator<?> i = c.iterator(); i.hasNext(); )
282 >            if (remove(i.next()))
283 >                modified = true;
284 >        return modified;
285      }
286 <    
286 >
287      /* ---------------- Relational operations -------------- */
288  
289      /**
290       * Returns an element greater than or equal to the given element, or
291 <     * <tt>null</tt> if there is no such element.
292 <     *
291 >     * {@code null} if there is no such element.
292 >     *
293       * @param o the value to match
294 <     * @return an element greater than or equal to given element, or <tt>null</tt>
295 <     * if there is no such element.
294 >     * @return an element greater than or equal to given element, or
295 >     * {@code null} if there is no such element
296       * @throws ClassCastException if o cannot be compared with the elements
297 <     *            currently in the set.
298 <     * @throws NullPointerException if o is <tt>null</tt>
297 >     *            currently in the set
298 >     * @throws NullPointerException if o is {@code null}
299       */
300      public E ceiling(E o) {
301          return m.ceilingKey(o);
302      }
303  
304      /**
305 <     * Returns an element strictly less than the given element, or <tt>null</tt> if
306 <     * there is no such element.
307 <     *
305 >     * Returns an element strictly less than the given element, or
306 >     * {@code null} if there is no such element.
307 >     *
308       * @param o the value to match
309       * @return the greatest element less than the given element, or
310 <     * <tt>null</tt> if there is no such element.
310 >     * {@code null} if there is no such element
311       * @throws ClassCastException if o cannot be compared with the elements
312 <     *            currently in the set.
313 <     * @throws NullPointerException if o is <tt>null</tt>.
312 >     *            currently in the set
313 >     * @throws NullPointerException if o is {@code null}
314       */
315      public E lower(E o) {
316          return m.lowerKey(o);
317      }
318  
319      /**
320 <     * Returns an element less than or equal to the given element, or <tt>null</tt>
321 <     * if there is no such element.
322 <     *
320 >     * Returns an element less than or equal to the given element, or
321 >     * {@code null} if there is no such element.
322 >     *
323       * @param o the value to match
324       * @return the greatest element less than or equal to given
325 <     * element, or <tt>null</tt> if there is no such element.
325 >     * element, or {@code null} if there is no such element
326       * @throws ClassCastException if o cannot be compared with the elements
327 <     *            currently in the set.
328 <     * @throws NullPointerException if o is <tt>null</tt>.
327 >     *            currently in the set
328 >     * @throws NullPointerException if o is {@code null}
329       */
330      public E floor(E o) {
331          return m.floorKey(o);
332      }
333  
334      /**
335 <     * Returns an element strictly greater than the given element, or <tt>null</tt>
336 <     * if there is no such element.
337 <     *
335 >     * Returns an element strictly greater than the given element, or
336 >     * {@code null} if there is no such element.
337 >     *
338       * @param o the value to match
339       * @return the least element greater than the given element, or
340 <     * <tt>null</tt> if there is no such element.
340 >     * {@code null} if there is no such element
341       * @throws ClassCastException if o cannot be compared with the elements
342 <     *            currently in the set.
343 <     * @throws NullPointerException if o is <tt>null</tt>.
342 >     *            currently in the set
343 >     * @throws NullPointerException if o is {@code null}
344       */
345      public E higher(E o) {
346          return m.higherKey(o);
# Line 278 | Line 349 | public class ConcurrentSkipListSet<E>
349      /**
350       * Retrieves and removes the first (lowest) element.
351       *
352 <     * @return the least element, or <tt>null</tt> if empty.
352 >     * @return the least element, or {@code null} if empty
353       */
354      public E pollFirst() {
355 <        return m.removeFirstKey();
355 >        return m.pollFirstKey();
356      }
357  
358      /**
359       * Retrieves and removes the last (highest) element.
360       *
361 <     * @return the last element, or <tt>null</tt> if empty.
361 >     * @return the last element, or {@code null} if empty
362       */
363      public E pollLast() {
364 <        return m.removeLastKey();
364 >        return m.pollLastKey();
365      }
366  
367  
# Line 298 | Line 369 | public class ConcurrentSkipListSet<E>
369  
370  
371      /**
372 <     * Returns the comparator used to order this set, or <tt>null</tt>
372 >     * Returns the comparator used to order this set, or {@code null}
373       * if this set uses its elements natural ordering.
374       *
375 <     * @return the comparator used to order this set, or <tt>null</tt>
376 <     * if this set uses its elements natural ordering.
375 >     * @return the comparator used to order this set, or {@code null}
376 >     * if this set uses its elements natural ordering
377       */
378      public Comparator<? super E> comparator() {
379          return m.comparator();
# Line 311 | Line 382 | public class ConcurrentSkipListSet<E>
382      /**
383       * Returns the first (lowest) element currently in this set.
384       *
385 <     * @return the first (lowest) element currently in this set.
386 <     * @throws    NoSuchElementException sorted set is empty.
385 >     * @return the first (lowest) element currently in this set
386 >     * @throws    NoSuchElementException sorted set is empty
387       */
388      public E first() {
389          return m.firstKey();
# Line 321 | Line 392 | public class ConcurrentSkipListSet<E>
392      /**
393       * Returns the last (highest) element currently in this set.
394       *
395 <     * @return the last (highest) element currently in this set.
396 <     * @throws    NoSuchElementException sorted set is empty.
395 >     * @return the last (highest) element currently in this set
396 >     * @throws    NoSuchElementException sorted set is empty
397       */
398      public E last() {
399          return m.lastKey();
400      }
401  
402 +
403 +
404      /**
405       * Returns a view of the portion of this set whose elements range from
406 <     * <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive.  (If
407 <     * <tt>fromElement</tt> and <tt>toElement</tt> are equal, the returned
406 >     * {@code fromElement}, inclusive, to {@code toElement}, exclusive.  (If
407 >     * {@code fromElement} and {@code toElement} are equal, the returned
408       * sorted set is empty.)  The returned sorted set is backed by this set,
409       * so changes in the returned sorted set are reflected in this set, and
410 <     * vice-versa.
411 <     * @param fromElement low endpoint (inclusive) of the subSet.
412 <     * @param toElement high endpoint (exclusive) of the subSet.
410 >     * vice-versa.
411 >     * @param fromElement low endpoint (inclusive) of the subSet
412 >     * @param toElement high endpoint (exclusive) of the subSet
413       * @return a view of the portion of this set whose elements range from
414 <     *         <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>,
415 <     *         exclusive.
416 <     * @throws ClassCastException if <tt>fromElement</tt> and
417 <     *         <tt>toElement</tt> cannot be compared to one another using
414 >     *         {@code fromElement}, inclusive, to {@code toElement},
415 >     *         exclusive
416 >     * @throws ClassCastException if {@code fromElement} and
417 >     *         {@code toElement} cannot be compared to one another using
418       *         this set's comparator (or, if the set has no comparator,
419 <     *         using natural ordering).
420 <     * @throws IllegalArgumentException if <tt>fromElement</tt> is
421 <     * greater than <tt>toElement</tt>.
422 <     * @throws NullPointerException if <tt>fromElement</tt> or
423 <     *         <tt>toElement</tt> is <tt>null</tt>.
419 >     *         using natural ordering)
420 >     * @throws IllegalArgumentException if {@code fromElement} is
421 >     * greater than {@code toElement}
422 >     * @throws NullPointerException if {@code fromElement} or
423 >     *         {@code toElement} is {@code null}
424       */
425      public NavigableSet<E> subSet(E fromElement, E toElement) {
426 <        return new ConcurrentSkipListSubSet<E>(m, fromElement, toElement);
426 >        return new ConcurrentSkipListSubSet<E>(m, fromElement, toElement);
427      }
428  
429      /**
430       * Returns a view of the portion of this set whose elements are strictly
431 <     * less than <tt>toElement</tt>.  The returned sorted set is backed by
431 >     * less than {@code toElement}.  The returned sorted set is backed by
432       * this set, so changes in the returned sorted set are reflected in this
433 <     * set, and vice-versa.  
434 <     * @param toElement high endpoint (exclusive) of the headSet.
433 >     * set, and vice-versa.
434 >     * @param toElement high endpoint (exclusive) of the headSet
435       * @return a view of the portion of this set whose elements are strictly
436 <     *         less than toElement.
437 <     * @throws ClassCastException if <tt>toElement</tt> is not compatible
436 >     *         less than toElement
437 >     * @throws ClassCastException if {@code toElement} is not compatible
438       *         with this set's comparator (or, if the set has no comparator,
439 <     *         if <tt>toElement</tt> does not implement <tt>Comparable</tt>).
440 <     * @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt>.
439 >     *         if {@code toElement} does not implement {@code Comparable})
440 >     * @throws NullPointerException if {@code toElement} is {@code null}
441       */
442      public NavigableSet<E> headSet(E toElement) {
443 <        return new ConcurrentSkipListSubSet<E>(m, null, toElement);
443 >        return new ConcurrentSkipListSubSet<E>(m, null, toElement);
444      }
445  
446  
447      /**
448       * Returns a view of the portion of this set whose elements are
449 <     * greater than or equal to <tt>fromElement</tt>.  The returned
449 >     * greater than or equal to {@code fromElement}.  The returned
450       * sorted set is backed by this set, so changes in the returned
451       * sorted set are reflected in this set, and vice-versa.
452 <     * @param fromElement low endpoint (inclusive) of the tailSet.
452 >     * @param fromElement low endpoint (inclusive) of the tailSet
453       * @return a view of the portion of this set whose elements are
454 <     * greater than or equal to <tt>fromElement</tt>.
455 <     * @throws ClassCastException if <tt>fromElement</tt> is not
454 >     * greater than or equal to {@code fromElement}
455 >     * @throws ClassCastException if {@code fromElement} is not
456       * compatible with this set's comparator (or, if the set has no
457 <     * comparator, if <tt>fromElement</tt> does not implement
458 <     * <tt>Comparable</tt>).
459 <     * @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt>.
457 >     * comparator, if {@code fromElement} does not implement
458 >     * {@code Comparable})
459 >     * @throws NullPointerException if {@code fromElement} is {@code null}
460       */
461      public NavigableSet<E> tailSet(E fromElement) {
462 <        return new ConcurrentSkipListSubSet<E>(m, fromElement, null);
462 >        return new ConcurrentSkipListSubSet<E>(m, fromElement, null);
463      }
464  
465      /**
# Line 396 | Line 469 | public class ConcurrentSkipListSet<E>
469       * underlying sets, differing in that elements outside their range are
470       * ignored, and attempts to add elements outside their ranges result
471       * in {@link IllegalArgumentException}.  Instances of this class are
472 <     * constructed only using the <tt>subSet</tt>, <tt>headSet</tt>, and
473 <     * <tt>tailSet</tt> methods of their underlying sets.
401 <     *
472 >     * constructed only using the {@code subSet}, {@code headSet}, and
473 >     * {@code tailSet} methods of their underlying sets.
474       */
475 <    static class ConcurrentSkipListSubSet<E>
476 <        extends AbstractSet<E>
475 >    static class ConcurrentSkipListSubSet<E>
476 >        extends AbstractSet<E>
477          implements NavigableSet<E>, java.io.Serializable {
478  
479          private static final long serialVersionUID = -7647078645896651609L;
480  
481 <        /** The underlying submap   */
481 >        /** The underlying submap  */
482          private final ConcurrentSkipListMap.ConcurrentSkipListSubMap<E,Object> s;
483 <        
483 >
484          /**
485 <         * Creates a new submap.
486 <         * @param fromElement inclusive least value, or <tt>null</tt> if from start
487 <         * @param toElement exclusive upper bound or <tt>null</tt> if to end
485 >         * Creates a new submap.
486 >         * @param fromElement inclusive least value, or {@code null} if from start
487 >         * @param toElement exclusive upper bound or {@code null} if to end
488           * @throws IllegalArgumentException if fromElement and toElement
489 <         * nonnull and fromElement greater than toElement
489 >         * non-null and fromElement greater than toElement
490           */
491 <        ConcurrentSkipListSubSet(ConcurrentSkipListMap<E,Object> map,
491 >        ConcurrentSkipListSubSet(ConcurrentSkipListMap<E,Object> map,
492                                   E fromElement, E toElement) {
493 <            s = new ConcurrentSkipListMap.ConcurrentSkipListSubMap<E,Object>(map, fromElement,
494 <                                                       toElement);
423 <        }
424 <
425 <        /**
426 <         * Returns the number of elements in this set.  If this set
427 <         * contains more than <tt>Integer.MAX_VALUE</tt> elements, it
428 <         * returns <tt>Integer.MAX_VALUE</tt>.
429 <         *
430 <         * <p>Beware that, unlike in most collections, this method is
431 <         * <em>NOT</em> a constant-time operation. Because of the
432 <         * asynchronous nature of these sets, determining the current
433 <         * number of elements requires traversing them all to count them.
434 <         * Additionally, it is possible for the size to change during
435 <         * execution of this method, in which case the returned result
436 <         * will be inaccurate. Thus, this method is typically not very
437 <         * useful in concurrent applications.
438 <         *
439 <         * @return  the number of elements in this set.
440 <         */
441 <        public int size() {
442 <            return s.size();
443 <        }
444 <        
445 <        /**
446 <         * Returns <tt>true</tt> if this set contains no elements.
447 <         * @return <tt>true</tt> if this set contains no elements.
448 <         */
449 <        public boolean isEmpty() {
450 <            return s.isEmpty();
451 <        }
452 <                                          
453 <        /**
454 <         * Returns <tt>true</tt> if this set contains the specified
455 <         * element.
456 <         *
457 <         * @param o the object to be checked for containment in this
458 <         * set.
459 <         * @return <tt>true</tt> if this set contains the specified
460 <         * element.
461 <         *
462 <         * @throws ClassCastException if the specified object cannot
463 <         * be compared with the elements currently in the set.
464 <         * @throws NullPointerException if o is <tt>null</tt>.
465 <         */
466 <        public boolean contains(Object o) {
467 <            return s.containsKey(o);
468 <        }
469 <
470 <
471 <        /**
472 <         * Adds the specified element to this set if it is not already
473 <         * present.
474 <         *
475 <         * @param o element to be added to this set.
476 <         * @return <tt>true</tt> if the set did not already contain
477 <         * the specified element.
478 <         *
479 <         * @throws ClassCastException if the specified object cannot
480 <         * be compared with the elements currently in the set.
481 <         * @throws IllegalArgumentException if o is outside the range
482 <         * of this subset.
483 <         * @throws NullPointerException if o is <tt>null</tt>.
484 <         */
485 <        public boolean add(E o) {
486 <            return s.put(o, Boolean.TRUE) == null;
487 <        }
488 <
489 <        /**
490 <         * Removes the specified element from this set if it is
491 <         * present.
492 <         *
493 <         * @param o object to be removed from this set, if present.
494 <         * @return <tt>true</tt> if the set contained the specified element.
495 <         *
496 <         * @throws ClassCastException if the specified object cannot
497 <         * be compared with the elements currently in the set.
498 <         * @throws NullPointerException if o is <tt>null</tt>.
499 <         */
500 <        public boolean remove(Object o) {
501 <            return s.remove(o) != null;
502 <        }
503 <
504 <        /**
505 <         * Removes all of the elements from this set.
506 <         */
507 <        public void clear() {
508 <            s.clear();
509 <        }
510 <
511 <        /**
512 <         * Returns an iterator over the elements in this set.  The elements
513 <         * are returned in ascending order.
514 <         *
515 <         * @return an iterator over the elements in this set.
516 <         */
517 <        public Iterator<E> iterator() {
518 <            return s.keySet().iterator();
519 <        }
520 <
521 <        /**
522 <         * Returns an element greater than or equal to the given
523 <         * element, or <tt>null</tt> if there is no such element.
524 <         *
525 <         * @param o the value to match
526 <         * @return an element greater than or equal to given element, or <tt>null</tt>
527 <         * if there is no such element.
528 <         * @throws ClassCastException if o cannot be compared with the
529 <         * elements currently in the set.
530 <         * @throws NullPointerException if o is <tt>null</tt>
531 <         */
532 <        public E ceiling(E o) {
533 <            E key = o;
534 <            E least = s.getLeast();
535 <            if (least != null && s.getMap().compare(o, least) < 0)
536 <                key = least;
537 <            E k = s.getMap().ceilingKey(key);
538 <            return (k != null && s.inHalfOpenRange(k))? k : null;
539 <        }
540 <
541 <        /**
542 <         * Returns an element strictly less than the given element, or <tt>null</tt> if
543 <         * there is no such element.
544 <         *
545 <         * @param o the value to match
546 <         * @return the greatest element less than the given element, or
547 <         * <tt>null</tt> if there is no such element.
548 <         * @throws ClassCastException if o cannot be compared with the
549 <         * elements currently in the set.
550 <         * @throws NullPointerException if o is <tt>null</tt>.
551 <         */
552 <        public E lower(E o) {
553 <            E k = s.getMap().lowerKey(o);
554 <            return (k != null && s.inHalfOpenRange(k))? k : null;
555 <        }
556 <
557 <        /**
558 <         * Returns an element less than or equal to the given element, or <tt>null</tt>
559 <         * if there is no such element.
560 <         *
561 <         * @param o the value to match
562 <         * @return the greatest element less than or equal to given
563 <         * element, or <tt>null</tt> if there is no such element.
564 <         * @throws ClassCastException if o cannot be compared with the
565 <         * elements currently in the set.
566 <         * @throws NullPointerException if o is <tt>null</tt>.
567 <         */
568 <        public E floor(E o) {
569 <            E k = s.getMap().floorKey(o);
570 <            return (k != null && s.inHalfOpenRange(k))? k : null;
571 <        }
572 <
573 <        /**
574 <         * Returns an element strictly greater than the given element, or <tt>null</tt>
575 <         * if there is no such element.
576 <         *
577 <         * @param o the value to match
578 <         * @return the least element greater than the given element, or
579 <         * <tt>null</tt> if there is no such element.
580 <         * @throws ClassCastException if o cannot be compared with the
581 <         * elements currently in the set.
582 <         * @throws NullPointerException if o is <tt>null</tt>.
583 <         */
584 <        public E higher(E o) {
585 <            E k;
586 <            E least = s.getLeast();
587 <            if (least != null && s.getMap().compare(o, least) < 0)
588 <                k = s.getMap().ceilingKey(least);
589 <            else
590 <                k = s.getMap().higherKey(o);
591 <            return (k != null && s.inHalfOpenRange(k))? k : null;
592 <        }
593 <
594 <        /**
595 <         * Retrieves and removes the first (lowest) element.
596 <         *
597 <         * @return the first element, or <tt>null</tt> if empty.
598 <         */
599 <        public E pollFirst() {
600 <            for (;;) {
601 <                E k = s.lowestKey();
602 <                if (k == null)
603 <                    return null;
604 <                if (remove(k))
605 <                    return k;
606 <            }
607 <        }
608 <
609 <        /**
610 <         * Retrieves and removes the last (highest) element.
611 <         *
612 <         * @return the last element, or <tt>null</tt> if empty.
613 <         */
614 <        public E pollLast() {
615 <            for (;;) {
616 <                E k = s.highestKey();
617 <                if (k == null)
618 <                    return null;
619 <                if (remove(k))
620 <                    return k;
621 <            }
493 >            s = new ConcurrentSkipListMap.ConcurrentSkipListSubMap<E,Object>
494 >                (map, fromElement, toElement);
495          }
496  
497 <        /**
625 <         * Returns the comparator used to order this set, or <tt>null</tt>
626 <         * if this set uses its elements natural ordering.
627 <         *
628 <         * @return the comparator used to order this set, or <tt>null</tt>
629 <         * if this set uses its elements natural ordering.
630 <         */
631 <        public Comparator<? super E> comparator() {
632 <            return s.comparator();
633 <        }
634 <
635 <        /**
636 <         * Returns the first (lowest) element currently in this set.
637 <         *
638 <         * @return the first (lowest) element currently in this set.
639 <         * @throws    NoSuchElementException sorted set is empty.
640 <         */
641 <        public E first() {
642 <            return s.firstKey();
643 <        }
497 >        // subsubset construction
498  
499 <        /**
646 <         * Returns the last (highest) element currently in this set.
647 <         *
648 <         * @return the last (highest) element currently in this set.
649 <         * @throws    NoSuchElementException sorted set is empty.
650 <         */
651 <        public E last() {
652 <            return s.lastKey();
653 <        }
654 <
655 <        /**
656 <         * Returns a view of the portion of this set whose elements
657 <         * range from <tt>fromElement</tt>, inclusive, to
658 <         * <tt>toElement</tt>, exclusive.  (If <tt>fromElement</tt>
659 <         * and <tt>toElement</tt> are equal, the returned sorted set
660 <         * is empty.)  The returned sorted set is backed by this set,
661 <         * so changes in the returned sorted set are reflected in this
662 <         * set, and vice-versa.
663 <         * @param fromElement low endpoint (inclusive) of the subSet.
664 <         * @param toElement high endpoint (exclusive) of the subSet.
665 <         * @return a view of the portion of this set whose elements
666 <         * range from <tt>fromElement</tt>, inclusive, to
667 <         * <tt>toElement</tt>, exclusive.
668 <         * @throws ClassCastException if <tt>fromElement</tt> and
669 <         * <tt>toElement</tt> cannot be compared to one another using
670 <         * this set's comparator (or, if the set has no comparator,
671 <         * using natural ordering).
672 <         * @throws IllegalArgumentException if <tt>fromElement</tt> is
673 <         * greater than <tt>toElement</tt> or either key is outside
674 <         * the range of this set.
675 <         * @throws NullPointerException if <tt>fromElement</tt> or
676 <         *             <tt>toElement</tt> is <tt>null</tt>.
677 <         */
678 <        public NavigableSet<E> subSet(E fromElement,
679 <                                      E toElement) {
499 >        public NavigableSet<E> subSet(E fromElement, E toElement) {
500              if (!s.inOpenRange(fromElement) || !s.inOpenRange(toElement))
501                  throw new IllegalArgumentException("element out of range");
502 <            return new ConcurrentSkipListSubSet<E>(s.getMap(),
502 >            return new ConcurrentSkipListSubSet<E>(s.getMap(),
503                                                     fromElement, toElement);
504          }
505  
686        /**
687         * Returns a view of the portion of this set whose elements are
688         * strictly less than <tt>toElement</tt>.  The returned sorted set
689         * is backed by this set, so changes in the returned sorted set
690         * are reflected in this set, and vice-versa.
691         * @param toElement high endpoint (exclusive) of the headSet.
692         * @return a view of the portion of this set whose elements
693         * are strictly less than toElement.
694         * @throws ClassCastException if <tt>toElement</tt> is not
695         * compatible with this set's comparator (or, if the set has
696         * no comparator, if <tt>toElement</tt> does not implement
697         * <tt>Comparable</tt>).
698         * @throws IllegalArgumentException if <tt>toElement</tt> is
699         * outside the range of this set.
700         * @throws NullPointerException if <tt>toElement</tt> is
701         * <tt>null</tt>.
702         */
506          public NavigableSet<E> headSet(E toElement) {
507              E least = s.getLeast();
508              if (!s.inOpenRange(toElement))
509                  throw new IllegalArgumentException("element out of range");
510 <            return new ConcurrentSkipListSubSet<E>(s.getMap(),
510 >            return new ConcurrentSkipListSubSet<E>(s.getMap(),
511                                                     least, toElement);
512          }
513 <        
711 <        /**
712 <         * Returns a view of the portion of this set whose elements
713 <         * are greater than or equal to <tt>fromElement</tt>.  The
714 <         * returned sorted set is backed by this set, so changes in
715 <         * the returned sorted set are reflected in this set, and
716 <         * vice-versa.
717 <         * @param fromElement low endpoint (inclusive) of the tailSet.
718 <         * @return a view of the portion of this set whose elements
719 <         * are greater than or equal to <tt>fromElement</tt>.
720 <         * @throws ClassCastException if <tt>fromElement</tt> is not
721 <         * compatible with this set's comparator (or, if the set has
722 <         * no comparator, if <tt>fromElement</tt> does not implement
723 <         * <tt>Comparable</tt>).
724 <         * @throws IllegalArgumentException if <tt>fromElement</tt> is
725 <         * outside the range of this set.
726 <         * @throws NullPointerException if <tt>fromElement</tt> is
727 <         * <tt>null</tt>.
728 <         */
513 >
514          public NavigableSet<E> tailSet(E fromElement) {
515              E fence = s.getFence();
516              if (!s.inOpenRange(fromElement))
517                  throw new IllegalArgumentException("element out of range");
518 <            return new ConcurrentSkipListSubSet<E>(s.getMap(),
518 >            return new ConcurrentSkipListSubSet<E>(s.getMap(),
519                                                     fromElement, fence);
520          }
736    }
521  
522 +        // relays to submap methods
523  
524 < }    
524 >        public int size()                 { return s.size(); }
525 >        public boolean isEmpty()          { return s.isEmpty(); }
526 >        public boolean contains(Object o) { return s.containsKey(o); }
527 >        public void clear()               { s.clear(); }
528 >        public E first()                  { return s.firstKey(); }
529 >        public E last()                   { return s.lastKey(); }
530 >        public E ceiling(E o)             { return s.ceilingKey(o); }
531 >        public E lower(E o)               { return s.lowerKey(o); }
532 >        public E floor(E o)               { return s.floorKey(o); }
533 >        public E higher(E o)              { return s.higherKey(o); }
534 >        public boolean remove(Object o) { return s.remove(o)==Boolean.TRUE; }
535 >        public boolean add(E o)       { return s.put(o, Boolean.TRUE)==null; }
536 >        public Comparator<? super E> comparator() { return s.comparator(); }
537 >        public Iterator<E> iterator()     { return s.keySet().iterator(); }
538 >        public Iterator<E> descendingIterator() {
539 >            return s.descendingKeySet().iterator();
540 >        }
541 >        public E pollFirst() {
542 >            Map.Entry<E,?> e = s.pollFirstEntry();
543 >            return (e == null) ? null : e.getKey();
544 >        }
545 >        public E pollLast() {
546 >            Map.Entry<E,?> e = s.pollLastEntry();
547 >            return (e == null) ? null : e.getKey();
548 >        }
549 >
550 >    }
551 > }

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