/* * 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/publicdomain/zero/1.0/ */ package jsr166x; import java.util.*; /** * A {@link SortedSet} extended with navigation methods reporting * closest matches for given search targets. Methods lower, * floor, ceiling, and higher return keys * respectively less than, less than or equal, greater than or equal, * and greater than a given key, returning null if there is * no such key. A NavigableSet may be viewed and traversed * in either ascending or descending order. The Collection * iterator method returns an ascending Iterator and * the additional method descendingIterator returns * descending iterator. The performance of ascending traversals is * likely to be faster than descending traversals. This interface * additionally defines methods pollFirst and * pollLast that return and remove the lowest and highest key, * if one exists, else returning null. * *

The return values of navigation methods may be ambiguous in * implementations that permit null elements. However, even * in this case the result can be disambiguated by checking * contains(null). To avoid such issues, implementations of * this interface are encouraged not to permit insertion of * null elements. (Note that sorted sets of {@link * Comparable} elements intrinsically do not permit null.) * * @author Doug Lea * @param the type of elements maintained by this set */ public interface NavigableSet extends SortedSet { /** * 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 * and this set deas not permit null elements */ public E ceiling(E o); /** * 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 * and this set deas not permit null elements */ public E lower(E o); /** * 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. * and this set deas not permit null elements */ public E floor(E o); /** * 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 * and this set deas not permit null elements */ public E higher(E o); /** * Retrieves and removes the first (lowest) element. * * @return the first element, or null if empty. */ public E pollFirst(); /** * Retrieves and removes the last (highest) element. * * @return the last element, or null if empty. */ public E pollLast(); /** * Returns an iterator over the elements in this collection, in * descending order. * * @return an Iterator over the elements in this collection */ Iterator descendingIterator(); /** * 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. * @throws NullPointerException if fromElement or * toElement is null * and this set deas not permit null elements */ public NavigableSet subSet(E fromElement, E 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 NullPointerException if toElement is null * and this set deas not permit null elements */ public NavigableSet headSet(E 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 NullPointerException if fromElement is null * and this set deas not permit null elements */ public NavigableSet tailSet(E fromElement); }