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Revision **1.9** -
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*Mon May 16 06:27:52 2005 UTC*
(13 years, 2 months ago)
by *jsr166*

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Changes since**1.8: +108 -79 lines**

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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 elements * respectively less than, less than or equal, greater than or equal, * and greater than a given element, returning <tt>null</tt> if there is * no such element. 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 a * descending iterator. The performance of ascending traversals is * likely to be faster than descending traversals. This interface * additionally defines methods <tt>pollFirst</tt> and * <tt>pollLast</tt> that return and remove the lowest and highest * element, if one exists, else returning <tt>null</tt>. * Methods <tt>navigableSubSet</tt>, <tt>navigableHeadSet</tt>, and * <tt>navigableTailSet</tt> differ from the similarly named * <tt>SortedSet</tt> methods only in that the returned sets * are guaranteed to obey the <tt>NavigableSet</tt> interface. * * <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 to <em>not</em> permit insertion of * <tt>null</tt> elements. (Note that sorted sets of {@link * Comparable} elements intrinsically do not permit <tt>null</tt>.) * * <p>This interface is a member of the * <a href="{@docRoot}/../guide/collections/index.html"> * Java Collections Framework</a>. * * @author Doug Lea * @param <E> the type of elements maintained by this set * @since 1.6 */ public interface NavigableSet<E> extends SortedSet<E> { /** * Returns the greatest element in this set strictly less than the * given element, or <tt>null</tt> if there is no such element. * * @param e the value to match * @return the greatest element less than <tt>e</tt>, * or <tt>null</tt> if there is no such element * @throws ClassCastException if the specified element cannot be * compared with the elements currently in the set * @throws NullPointerException if the specified element is null * and this set does not permit null elements */ E lower(E e); /** * Returns the greatest element in this set less than or equal to * the given element, or <tt>null</tt> if there is no such element. * * @param e the value to match * @return the greatest element less than or equal to <tt>e</tt>, * or <tt>null</tt> if there is no such element * @throws ClassCastException if the specified element cannot be * compared with the elements currently in the set * @throws NullPointerException if the specified element is null * and this set does not permit null elements */ E floor(E e); /** * Returns the least element in this set greater than or equal to * the given element, or <tt>null</tt> if there is no such element. * * @param e the value to match * @return the least element greater than or equal to <tt>e</tt>, * or <tt>null</tt> if there is no such element * @throws ClassCastException if the specified element cannot be * compared with the elements currently in the set * @throws NullPointerException if the specified element is null * and this set does not permit null elements */ E ceiling(E e); /** * Returns the least element in this set strictly greater than the * given element, or <tt>null</tt> if there is no such element. * * @param e the value to match * @return the least element greater than <tt>e</tt>, * or <tt>null</tt> if there is no such element * @throws ClassCastException if the specified element cannot be * compared with the elements currently in the set * @throws NullPointerException if the specified element is null * and this set does not permit null elements */ E higher(E e); /** * Retrieves and removes the first (lowest) element. * * @return the first element, or <tt>null</tt> if this set is empty */ E pollFirst(); /** * Retrieves and removes the last (highest) element. * * @return the last element, or <tt>null</tt> if this set is empty */ E pollLast(); /** * Returns an iterator over the elements in this set, in * descending order. * * @return an <tt>Iterator</tt> over the elements in this set */ 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 set is empty.) The returned set is backed * by this set, so changes in the returned set are reflected in * this set, and vice-versa. The returned set supports all * optional set operations that this set supports. * * <p>The returned set will throw an <tt>IllegalArgumentException</tt> * on an attempt to insert an element outside its range. * * @param fromElement low endpoint (inclusive) of the returned set * @param toElement high endpoint (exclusive) of the returned set * @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). Implementations may, but are not required * to, throw this exception if <tt>fromElement</tt> or * <tt>toElement</tt> cannot be compared to elements currently in * the set. * @throws NullPointerException if <tt>fromElement</tt> or * <tt>toElement</tt> is null and this set does * not permit null elements * @throws IllegalArgumentException if <tt>fromElement</tt> is * greater than <tt>toElement</tt>; or if this set itself * has a restricted range, and <tt>fromElement</tt> or * <tt>toElement</tt> lies outside the bounds of the range. */ NavigableSet<E> navigableSubSet(E fromElement, E toElement); /** * Returns a view of the portion of this set whose elements are * strictly less than <tt>toElement</tt>. The returned set is * backed by this set, so changes in the returned set are * reflected in this set, and vice-versa. The returned set * supports all optional set operations that this set supports. * * <p>The returned set will throw an <tt>IllegalArgumentException</tt> * on an attempt to insert an element outside its range. * * @param toElement high endpoint (exclusive) of the returned set * @return a view of the portion of this set whose elements are strictly * less than <tt>toElement</tt> * @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 {@link Comparable}). * Implementations may, but are not required to, throw this * exception if <tt>toElement</tt> cannot be compared to elements * currently in the set. * @throws NullPointerException if <tt>toElement</tt> is null and * this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and <tt>toElement</tt> lies outside the * bounds of the range */ NavigableSet<E> navigableHeadSet(E toElement); /** * Returns a view of the portion of this set whose elements are * greater than or equal to <tt>fromElement</tt>. The returned * set is backed by this set, so changes in the returned set are * reflected in this set, and vice-versa. The returned set * supports all optional set operations that this set supports. * * <p>The returned set will throw an <tt>IllegalArgumentException</tt> * on an attempt to insert an element outside its range. * * @param fromElement low endpoint (inclusive) of the returned set * @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 {@link Comparable}). * Implementations may, but are not required to, throw this * exception if <tt>fromElement</tt> cannot be compared to elements * currently in the set. * @throws NullPointerException if <tt>fromElement</tt> is null * and this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and <tt>fromElement</tt> lies outside the * bounds of the range */ NavigableSet<E> navigableTailSet(E fromElement); }

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