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Revision **1.2** -
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*Tue Mar 8 12:27:06 2005 UTC*
(13 years, 3 months ago)
by *dl*

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/* * 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 */ package java.util; /** * A {@link SortedSet} extended with navigation methods reporting * closest matches for given search targets. Methods <tt>lower</tt>, * <tt>floor</tt>, <tt>ceiling</tt>, and <tt>higher</tt> return keys * respectively less than, less than or equal, greater than or equal, * and greater than a given key, returning <tt>null</tt> if there is * no such key. A <tt>NavigableSet</tt> may be viewed and traversed * in either ascending or descending order. The <tt>Collection</tt> * <tt>iterator</tt> method returns an ascending <tt>Iterator</tt> and * the additional method <tt>descendingIterator</tt> returns * descending iterator. The performance of ascending traversals is * likely to be faster than descending traversals. This interface * additionally defines methods <tt>pollFirst</tt> and * <t>pollLast</tt> that return and remove the lowest and highest key, * if one exists, else returning <tt>null</tt>. * * <p> The return values of navigation methods may be ambiguous in * implementations that permit <tt>null</tt> elements. However, even * in this case the result can be disambiguated by checking * <tt>contains(null)</tt>. To avoid such issues, implementations of * this interface are encouraged <em>not</em> to permit insertion of * <tt>null</tt> elements. (Note that sorted sets of {@link * Comparable} elements intrinsically do not permit <tt>null</tt>.) * * @author Doug Lea * @param <E> the type of elements maintained by this set */ public interface NavigableSet<E> extends SortedSet<E> { /** * Returns an element greater than or equal to the given element, or * <tt>null</tt> if there is no such element. * * @param o the value to match * @return an element greater than or equal to given element, or * <tt>null</tt> 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 <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public E ceiling(E o); /** * Returns an element strictly less than the given element, or * <tt>null</tt> if there is no such element. * * @param o the value to match * @return the greatest element less than the given element, or * <tt>null</tt> 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 <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public E lower(E o); /** * Returns an element less than or equal to the given element, or * <tt>null</tt> if there is no such element. * * @param o the value to match * @return the greatest element less than or equal to given * element, or <tt>null</tt> 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 <tt>null</tt>. * and this set does not permit <tt>null</tt> elements */ public E floor(E o); /** * Returns an element strictly greater than the given element, or * <tt>null</tt> if there is no such element. * * @param o the value to match * @return the least element greater than the given element, or * <tt>null</tt> 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 <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public E higher(E o); /** * Retrieves and removes the first (lowest) element. * * @return the first element, or <tt>null</tt> if empty. */ public E pollFirst(); /** * Retrieves and removes the last (highest) element. * * @return the last element, or <tt>null</tt> if empty. */ public E pollLast(); /** * Returns an iterator over the elements in this collection, in * descending order. * * @return an <tt>Iterator</tt> over the elements in this collection */ Iterator<E> descendingIterator(); /** * Returns a view of the portion of this set whose elements range from * <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, exclusive. (If * <tt>fromElement</tt> and <tt>toElement</tt> 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 * <tt>fromElement</tt>, inclusive, to <tt>toElement</tt>, * exclusive. * @throws ClassCastException if <tt>fromElement</tt> and * <tt>toElement</tt> cannot be compared to one another using * this set's comparator (or, if the set has no comparator, * using natural ordering). * @throws IllegalArgumentException if <tt>fromElement</tt> is * greater than <tt>toElement</tt>. * @throws NullPointerException if <tt>fromElement</tt> or * <tt>toElement</tt> is <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public NavigableSet<E> subSet(E fromElement, E toElement); /** * Returns a view of the portion of this set whose elements are strictly * less than <tt>toElement</tt>. 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 <tt>toElement</tt> is not compatible * with this set's comparator (or, if the set has no comparator, * if <tt>toElement</tt> does not implement <tt>Comparable</tt>). * @throws NullPointerException if <tt>toElement</tt> is <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public NavigableSet<E> headSet(E toElement); /** * Returns a view of the portion of this set whose elements are * greater than or equal to <tt>fromElement</tt>. 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 <tt>fromElement</tt>. * @throws ClassCastException if <tt>fromElement</tt> is not * compatible with this set's comparator (or, if the set has no * comparator, if <tt>fromElement</tt> does not implement * <tt>Comparable</tt>). * @throws NullPointerException if <tt>fromElement</tt> is <tt>null</tt> * and this set does not permit <tt>null</tt> elements */ public NavigableSet<E> tailSet(E fromElement); }

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