--- jsr166/src/jsr166x/ConcurrentSkipListSet.java 2004/09/06 17:01:54 1.2 +++ jsr166/src/jsr166x/ConcurrentSkipListSet.java 2011/03/15 19:47:02 1.12 @@ -1,10 +1,10 @@ /* * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at - * http://creativecommons.org/licenses/publicdomain + * http://creativecommons.org/publicdomain/zero/1.0/ */ -package jsr166x; +package jsr166x; import java.util.*; import java.util.concurrent.*; @@ -24,19 +24,24 @@ import java.util.concurrent.*; * threads. Iterators are weakly consistent, returning elements * reflecting the state of the set at some point at or since the * creation of the iterator. They do not throw {@link - * ConcurrentModificationException}, and may procede concurrently with + * ConcurrentModificationException}, and may proceed concurrently with * other operations. * *

Beware that, unlike in most collections, the size - * method is NOT a constant-time operation. Because of the + * method is not a constant-time operation. Because of the * asynchronous nature of these sets, determining the current number - * of elements requires a traversal of the elements. + * of elements requires a traversal of the elements. Additionally, the + * bulk operations addAll, removeAll, + * <retainAll, and tt>containsAll are not + * guaranteed to be performed atomically. For example, an iterator + * operating concurrently with an addAll operation might view + * only some of the added elements. * *

This class and its iterators implement all of the * optional methods of the {@link Set} and {@link Iterator} * interfaces. Like most other concurrent collection implementations, * this class does not permit the use of null elements. - * because null arguments and return values cannot be reliably + * because null arguments and return values cannot be reliably * distinguished from the absence of elements. * * @author Doug Lea @@ -55,11 +60,11 @@ public class ConcurrentSkipListSet * fields of underlying map, but enables this field to be declared * final, which is necessary for thread safety. */ - private final ConcurrentSkipListMap m; + private final ConcurrentSkipListMap m; /** * Constructs a new, empty set, sorted according to the elements' natural - * order. + * order. */ public ConcurrentSkipListSet() { m = new ConcurrentSkipListMap(); @@ -67,7 +72,7 @@ public class ConcurrentSkipListSet /** * Constructs a new, empty set, sorted according to the specified - * comparator. + * comparator. * * @param c the comparator that will be used to sort this set. A * null value indicates that the elements' natural @@ -85,7 +90,8 @@ public class ConcurrentSkipListSet * * @throws ClassCastException if the elements in the specified * collection are not comparable, or are not mutually comparable. - * @throws NullPointerException if the specified collection is null. + * @throws NullPointerException if the specified collection is + * null. */ public ConcurrentSkipListSet(Collection c) { m = new ConcurrentSkipListMap(); @@ -97,7 +103,8 @@ public class ConcurrentSkipListSet * sorted set, sorted according to the same ordering. * * @param s sorted set whose elements will comprise the new set. - * @throws NullPointerException if the specified sorted set is null. + * @throws NullPointerException if the specified sorted set is + * null. */ public ConcurrentSkipListSet(SortedSet s) { m = new ConcurrentSkipListMap(s.comparator()); @@ -112,11 +119,11 @@ public class ConcurrentSkipListSet */ public Object clone() { ConcurrentSkipListSet clone = null; - try { - clone = (ConcurrentSkipListSet) super.clone(); - } catch (CloneNotSupportedException e) { - throw new InternalError(); - } + try { + clone = (ConcurrentSkipListSet) super.clone(); + } catch (CloneNotSupportedException e) { + throw new InternalError(); + } clone.m.initialize(); clone.addAll(this); @@ -142,7 +149,7 @@ public class ConcurrentSkipListSet * @return the number of elements in this set. */ public int size() { - return m.size(); + return m.size(); } /** @@ -150,7 +157,7 @@ public class ConcurrentSkipListSet * @return true if this set contains no elements. */ public boolean isEmpty() { - return m.isEmpty(); + return m.isEmpty(); } /** @@ -160,11 +167,11 @@ public class ConcurrentSkipListSet * @return true if this set contains the specified element. * * @throws ClassCastException if the specified object cannot be compared - * with the elements currently in the set. + * with the elements currently in the set. * @throws NullPointerException if o is null. */ public boolean contains(Object o) { - return m.containsKey(o); + return m.containsKey(o); } /** @@ -175,11 +182,11 @@ public class ConcurrentSkipListSet * element. * * @throws ClassCastException if the specified object cannot be compared - * with the elements currently in the set. + * with the elements currently in the set. * @throws NullPointerException if o is null. */ public boolean add(E o) { - return m.putIfAbsent(o, Boolean.TRUE) == null; + return m.putIfAbsent(o, Boolean.TRUE) == null; } /** @@ -189,18 +196,18 @@ public class ConcurrentSkipListSet * @return true if the set contained the specified element. * * @throws ClassCastException if the specified object cannot be compared - * with the elements currently in the set. + * with the elements currently in the set. * @throws NullPointerException if o is null. */ public boolean remove(Object o) { - return m.removep(o); + return m.removep(o); } /** * Removes all of the elements from this set. */ public void clear() { - m.clear(); + m.clear(); } /** @@ -210,18 +217,82 @@ public class ConcurrentSkipListSet * @return an iterator over the elements in this set. */ public Iterator iterator() { - return m.keyIterator(); + return m.keyIterator(); + } + + /** + * Returns an iterator over the elements in this set. The elements + * are returned in descending order. + * + * @return an iterator over the elements in this set. + */ + public Iterator descendingIterator() { + return m.descendingKeyIterator(); } - + + /* ---------------- AbstractSet Overrides -------------- */ + + /** + * Compares the specified object with this set for equality. Returns + * true if the specified object is also a set, the two sets + * have the same size, and every member of the specified set is + * contained in this set (or equivalently, every member of this set is + * contained in the specified set). This definition ensures that the + * equals method works properly across different implementations of the + * set interface. + * + * @param o Object to be compared for equality with this set. + * @return true if the specified Object is equal to this set. + */ + public boolean equals(Object o) { + // Override AbstractSet version to avoid calling size() + if (o == this) + return true; + if (!(o instanceof Set)) + return false; + Collection c = (Collection) o; + try { + return containsAll(c) && c.containsAll(this); + } catch (ClassCastException unused) { + return false; + } catch (NullPointerException unused) { + return false; + } + } + + /** + * Removes from this set all of its elements that are contained in + * the specified collection. If the specified collection is also + * a set, this operation effectively modifies this set so that its + * value is the asymmetric set difference of the two sets. + * + * @param c collection that defines which elements will be removed from + * this set. + * @return true if this set changed as a result of the call. + * + * @throws ClassCastException if the types of one or more elements in this + * set are incompatible with the specified collection + * @throws NullPointerException if the specified collection, or any + * of its elements are null. + */ + public boolean removeAll(Collection c) { + // Override AbstractSet version to avoid unnecessary call to size() + boolean modified = false; + for (Iterator i = c.iterator(); i.hasNext(); ) + if (remove(i.next())) + modified = true; + return modified; + } + /* ---------------- Relational operations -------------- */ /** * Returns an element greater than or equal to the given element, or - * null if there is no such element. - * + * null if there is no such element. + * * @param o the value to match - * @return an element greater than or equal to given element, or null - * if there is no such element. + * @return an element greater than or equal to given element, or + * null if there is no such element. * @throws ClassCastException if o cannot be compared with the elements * currently in the set. * @throws NullPointerException if o is null @@ -231,12 +302,12 @@ public class ConcurrentSkipListSet } /** - * Returns an element strictly less than the given element, or null if - * there is no such element. - * + * Returns an element strictly less than the given element, or + * null if there is no such element. + * * @param o the value to match * @return the greatest element less than the given element, or - * null if there is no such element. + * null if there is no such element. * @throws ClassCastException if o cannot be compared with the elements * currently in the set. * @throws NullPointerException if o is null. @@ -246,12 +317,12 @@ public class ConcurrentSkipListSet } /** - * Returns an element less than or equal to the given element, or null - * if there is no such element. - * + * Returns an element less than or equal to the given element, or + * null if there is no such element. + * * @param o the value to match * @return the greatest element less than or equal to given - * element, or null if there is no such element. + * element, or null if there is no such element. * @throws ClassCastException if o cannot be compared with the elements * currently in the set. * @throws NullPointerException if o is null. @@ -261,12 +332,12 @@ public class ConcurrentSkipListSet } /** - * Returns an element strictly greater than the given element, or null - * if there is no such element. - * + * Returns an element strictly greater than the given element, or + * null if there is no such element. + * * @param o the value to match * @return the least element greater than the given element, or - * null if there is no such element. + * null if there is no such element. * @throws ClassCastException if o cannot be compared with the elements * currently in the set. * @throws NullPointerException if o is null. @@ -281,7 +352,7 @@ public class ConcurrentSkipListSet * @return the least element, or null if empty. */ public E pollFirst() { - return m.removeFirstKey(); + return m.pollFirstKey(); } /** @@ -290,7 +361,7 @@ public class ConcurrentSkipListSet * @return the last element, or null if empty. */ public E pollLast() { - return m.removeLastKey(); + return m.pollLastKey(); } @@ -328,18 +399,20 @@ public class ConcurrentSkipListSet return m.lastKey(); } + + /** * Returns a view of the portion of this set whose elements range from * fromElement, inclusive, to toElement, exclusive. (If * fromElement and toElement are equal, the returned * sorted set is empty.) The returned sorted set is backed by this set, * so changes in the returned sorted set are reflected in this set, and - * vice-versa. + * vice-versa. * @param fromElement low endpoint (inclusive) of the subSet. * @param toElement high endpoint (exclusive) of the subSet. * @return a view of the portion of this set whose elements range from - * fromElement, inclusive, to toElement, - * exclusive. + * fromElement, inclusive, to toElement, + * exclusive. * @throws ClassCastException if fromElement and * toElement cannot be compared to one another using * this set's comparator (or, if the set has no comparator, @@ -347,27 +420,27 @@ public class ConcurrentSkipListSet * @throws IllegalArgumentException if fromElement is * greater than toElement. * @throws NullPointerException if fromElement or - * toElement is null. + * toElement is null. */ public NavigableSet subSet(E fromElement, E toElement) { - return new ConcurrentSkipListSubSet(m, fromElement, toElement); + return new ConcurrentSkipListSubSet(m, fromElement, toElement); } /** * Returns a view of the portion of this set whose elements are strictly * less than toElement. The returned sorted set is backed by * this set, so changes in the returned sorted set are reflected in this - * set, and vice-versa. + * set, and vice-versa. * @param toElement high endpoint (exclusive) of the headSet. * @return a view of the portion of this set whose elements are strictly - * less than toElement. + * less than toElement. * @throws ClassCastException if toElement is not compatible * with this set's comparator (or, if the set has no comparator, * if toElement does not implement Comparable). * @throws NullPointerException if toElement is null. */ public NavigableSet headSet(E toElement) { - return new ConcurrentSkipListSubSet(m, null, toElement); + return new ConcurrentSkipListSubSet(m, null, toElement); } @@ -386,7 +459,7 @@ public class ConcurrentSkipListSet * @throws NullPointerException if fromElement is null. */ public NavigableSet tailSet(E fromElement) { - return new ConcurrentSkipListSubSet(m, fromElement, null); + return new ConcurrentSkipListSubSet(m, fromElement, null); } /** @@ -400,340 +473,80 @@ public class ConcurrentSkipListSet * tailSet methods of their underlying sets. * */ - static class ConcurrentSkipListSubSet - extends AbstractSet + static class ConcurrentSkipListSubSet + extends AbstractSet implements NavigableSet, java.io.Serializable { private static final long serialVersionUID = -7647078645896651609L; - /** The underlying submap */ + /** The underlying submap */ private final ConcurrentSkipListMap.ConcurrentSkipListSubMap s; - + /** - * Creates a new submap. - * @param fromElement inclusive least value, or null if from start - * @param toElement exclusive upper bound or null if to end + * Creates a new submap. + * @param fromElement inclusive least value, or null if from start + * @param toElement exclusive upper bound or null if to end * @throws IllegalArgumentException if fromElement and toElement - * nonnull and fromElement greater than toElement + * non-null and fromElement greater than toElement */ - ConcurrentSkipListSubSet(ConcurrentSkipListMap map, + ConcurrentSkipListSubSet(ConcurrentSkipListMap map, E fromElement, E toElement) { - s = new ConcurrentSkipListMap.ConcurrentSkipListSubMap(map, fromElement, - toElement); + s = new ConcurrentSkipListMap.ConcurrentSkipListSubMap + (map, fromElement, toElement); } - /** - * Returns the number of elements in this set. If this set - * contains more than Integer.MAX_VALUE elements, it - * returns Integer.MAX_VALUE. - * - *

Beware that, unlike in most collections, this method is - * NOT a constant-time operation. Because of the - * asynchronous nature of these sets, determining the current - * number of elements requires traversing them all to count them. - * Additionally, it is possible for the size to change during - * execution of this method, in which case the returned result - * will be inaccurate. Thus, this method is typically not very - * useful in concurrent applications. - * - * @return the number of elements in this set. - */ - public int size() { - return s.size(); - } - - /** - * Returns true if this set contains no elements. - * @return true if this set contains no elements. - */ - public boolean isEmpty() { - return s.isEmpty(); - } - - /** - * Returns true if this set contains the specified - * element. - * - * @param o the object to be checked for containment in this - * set. - * @return true if this set contains the specified - * element. - * - * @throws ClassCastException if the specified object cannot - * be compared with the elements currently in the set. - * @throws NullPointerException if o is null. - */ - public boolean contains(Object o) { - return s.containsKey(o); - } - - - /** - * Adds the specified element to this set if it is not already - * present. - * - * @param o element to be added to this set. - * @return true if the set did not already contain - * the specified element. - * - * @throws ClassCastException if the specified object cannot - * be compared with the elements currently in the set. - * @throws IllegalArgumentException if o is outside the range - * of this subset. - * @throws NullPointerException if o is null. - */ - public boolean add(E o) { - return s.put(o, Boolean.TRUE) == null; - } - - /** - * Removes the specified element from this set if it is - * present. - * - * @param o object to be removed from this set, if present. - * @return true if the set contained the specified element. - * - * @throws ClassCastException if the specified object cannot - * be compared with the elements currently in the set. - * @throws NullPointerException if o is null. - */ - public boolean remove(Object o) { - return s.remove(o) != null; - } + // subsubset construction - /** - * Removes all of the elements from this set. - */ - public void clear() { - s.clear(); - } - - /** - * Returns an iterator over the elements in this set. The elements - * are returned in ascending order. - * - * @return an iterator over the elements in this set. - */ - public Iterator iterator() { - return s.keySet().iterator(); - } - - /** - * Returns an element greater than or equal to the given - * element, or null if there is no such element. - * - * @param o the value to match - * @return an element greater than or equal to given element, or null - * if there is no such element. - * @throws ClassCastException if o cannot be compared with the - * elements currently in the set. - * @throws NullPointerException if o is null - */ - public E ceiling(E o) { - E key = o; - E least = s.getLeast(); - if (least != null && s.getMap().compare(o, least) < 0) - key = least; - E k = s.getMap().ceilingKey(key); - return (k != null && s.inHalfOpenRange(k))? k : null; - } - - /** - * Returns an element strictly less than the given element, or null if - * there is no such element. - * - * @param o the value to match - * @return the greatest element less than the given element, or - * null if there is no such element. - * @throws ClassCastException if o cannot be compared with the - * elements currently in the set. - * @throws NullPointerException if o is null. - */ - public E lower(E o) { - E k = s.getMap().lowerKey(o); - return (k != null && s.inHalfOpenRange(k))? k : null; - } - - /** - * Returns an element less than or equal to the given element, or null - * if there is no such element. - * - * @param o the value to match - * @return the greatest element less than or equal to given - * element, or null if there is no such element. - * @throws ClassCastException if o cannot be compared with the - * elements currently in the set. - * @throws NullPointerException if o is null. - */ - public E floor(E o) { - E k = s.getMap().floorKey(o); - return (k != null && s.inHalfOpenRange(k))? k : null; - } - - /** - * Returns an element strictly greater than the given element, or null - * if there is no such element. - * - * @param o the value to match - * @return the least element greater than the given element, or - * null if there is no such element. - * @throws ClassCastException if o cannot be compared with the - * elements currently in the set. - * @throws NullPointerException if o is null. - */ - public E higher(E o) { - E k; - E least = s.getLeast(); - if (least != null && s.getMap().compare(o, least) < 0) - k = s.getMap().ceilingKey(least); - else - k = s.getMap().higherKey(o); - return (k != null && s.inHalfOpenRange(k))? k : null; - } - - /** - * Retrieves and removes the first (lowest) element. - * - * @return the first element, or null if empty. - */ - public E pollFirst() { - for (;;) { - E k = s.lowestKey(); - if (k == null) - return null; - if (remove(k)) - return k; - } - } - - /** - * Retrieves and removes the last (highest) element. - * - * @return the last element, or null if empty. - */ - public E pollLast() { - for (;;) { - E k = s.highestKey(); - if (k == null) - return null; - if (remove(k)) - return k; - } - } - - /** - * Returns the comparator used to order this set, or null - * if this set uses its elements natural ordering. - * - * @return the comparator used to order this set, or null - * if this set uses its elements natural ordering. - */ - public Comparator comparator() { - return s.comparator(); - } - - /** - * Returns the first (lowest) element currently in this set. - * - * @return the first (lowest) element currently in this set. - * @throws NoSuchElementException sorted set is empty. - */ - public E first() { - return s.firstKey(); - } - - /** - * Returns the last (highest) element currently in this set. - * - * @return the last (highest) element currently in this set. - * @throws NoSuchElementException sorted set is empty. - */ - public E last() { - return s.lastKey(); - } - - /** - * Returns a view of the portion of this set whose elements - * range from fromElement, inclusive, to - * toElement, exclusive. (If fromElement - * and toElement are equal, the returned sorted set - * is empty.) The returned sorted set is backed by this set, - * so changes in the returned sorted set are reflected in this - * set, and vice-versa. - * @param fromElement low endpoint (inclusive) of the subSet. - * @param toElement high endpoint (exclusive) of the subSet. - * @return a view of the portion of this set whose elements - * range from fromElement, inclusive, to - * toElement, exclusive. - * @throws ClassCastException if fromElement and - * toElement cannot be compared to one another using - * this set's comparator (or, if the set has no comparator, - * using natural ordering). - * @throws IllegalArgumentException if fromElement is - * greater than toElement or either key is outside - * the range of this set. - * @throws NullPointerException if fromElement or - * toElement is null. - */ - public NavigableSet subSet(E fromElement, - E toElement) { + public NavigableSet subSet(E fromElement, E toElement) { if (!s.inOpenRange(fromElement) || !s.inOpenRange(toElement)) throw new IllegalArgumentException("element out of range"); - return new ConcurrentSkipListSubSet(s.getMap(), + return new ConcurrentSkipListSubSet(s.getMap(), fromElement, toElement); } - /** - * Returns a view of the portion of this set whose elements are - * strictly less than toElement. The returned sorted set - * is backed by this set, so changes in the returned sorted set - * are reflected in this set, and vice-versa. - * @param toElement high endpoint (exclusive) of the headSet. - * @return a view of the portion of this set whose elements - * are strictly less than toElement. - * @throws ClassCastException if toElement is not - * compatible with this set's comparator (or, if the set has - * no comparator, if toElement does not implement - * Comparable). - * @throws IllegalArgumentException if toElement is - * outside the range of this set. - * @throws NullPointerException if toElement is - * null. - */ public NavigableSet headSet(E toElement) { E least = s.getLeast(); if (!s.inOpenRange(toElement)) throw new IllegalArgumentException("element out of range"); - return new ConcurrentSkipListSubSet(s.getMap(), + return new ConcurrentSkipListSubSet(s.getMap(), least, toElement); } - - /** - * Returns a view of the portion of this set whose elements - * are greater than or equal to fromElement. The - * returned sorted set is backed by this set, so changes in - * the returned sorted set are reflected in this set, and - * vice-versa. - * @param fromElement low endpoint (inclusive) of the tailSet. - * @return a view of the portion of this set whose elements - * are greater than or equal to fromElement. - * @throws ClassCastException if fromElement is not - * compatible with this set's comparator (or, if the set has - * no comparator, if fromElement does not implement - * Comparable). - * @throws IllegalArgumentException if fromElement is - * outside the range of this set. - * @throws NullPointerException if fromElement is - * null. - */ + public NavigableSet tailSet(E fromElement) { E fence = s.getFence(); if (!s.inOpenRange(fromElement)) throw new IllegalArgumentException("element out of range"); - return new ConcurrentSkipListSubSet(s.getMap(), + return new ConcurrentSkipListSubSet(s.getMap(), fromElement, fence); } - } + // relays to submap methods -} + public int size() { return s.size(); } + public boolean isEmpty() { return s.isEmpty(); } + public boolean contains(Object o) { return s.containsKey(o); } + public void clear() { s.clear(); } + public E first() { return s.firstKey(); } + public E last() { return s.lastKey(); } + public E ceiling(E o) { return s.ceilingKey(o); } + public E lower(E o) { return s.lowerKey(o); } + public E floor(E o) { return s.floorKey(o); } + public E higher(E o) { return s.higherKey(o); } + public boolean remove(Object o) { return s.remove(o)==Boolean.TRUE; } + public boolean add(E o) { return s.put(o, Boolean.TRUE)==null; } + public Comparator comparator() { return s.comparator(); } + public Iterator iterator() { return s.keySet().iterator(); } + public Iterator descendingIterator() { + return s.descendingKeySet().iterator(); + } + public E pollFirst() { + Map.Entry e = s.pollFirstEntry(); + return (e == null) ? null : e.getKey(); + } + public E pollLast() { + Map.Entry e = s.pollLastEntry(); + return (e == null) ? null : e.getKey(); + } + + } +}