Java tutorial
/* * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Written by Doug Lea and Josh Bloch 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 java.util; /** * A {@link SortedSet} extended with navigation methods reporting * closest matches for given search targets. Methods {@link #lower}, * {@link #floor}, {@link #ceiling}, and {@link #higher} return elements * respectively less than, less than or equal, greater than or equal, * and greater than a given element, returning {@code null} if there * is no such element. * * <p>A {@code NavigableSet} may be accessed and traversed in either * ascending or descending order. The {@link #descendingSet} method * returns a view of the set with the senses of all relational and * directional methods inverted. The performance of ascending * operations and views is likely to be faster than that of descending * ones. This interface additionally defines methods {@link * #pollFirst} and {@link #pollLast} that return and remove the lowest * and highest element, if one exists, else returning {@code null}. * Methods * {@link #subSet(Object, boolean, Object, boolean) subSet(E, boolean, E, boolean)}, * {@link #headSet(Object, boolean) headSet(E, boolean)}, and * {@link #tailSet(Object, boolean) tailSet(E, boolean)} * differ from the like-named {@code SortedSet} methods in accepting * additional arguments describing whether lower and upper bounds are * inclusive versus exclusive. Subsets of any {@code NavigableSet} * must implement the {@code NavigableSet} interface. * * <p>The return values of navigation methods may be ambiguous in * implementations that permit {@code null} elements. However, even * in this case the result can be disambiguated by checking * {@code contains(null)}. To avoid such issues, implementations of * this interface are encouraged to <em>not</em> permit insertion of * {@code null} elements. (Note that sorted sets of {@link * Comparable} elements intrinsically do not permit {@code null}.) * * <p>Methods * {@link #subSet(Object, Object) subSet(E, E)}, * {@link #headSet(Object) headSet(E)}, and * {@link #tailSet(Object) tailSet(E)} * are specified to return {@code SortedSet} to allow existing * implementations of {@code SortedSet} to be compatibly retrofitted to * implement {@code NavigableSet}, but extensions and implementations * of this interface are encouraged to override these methods to return * {@code NavigableSet}. * * <p>This interface is a member of the * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> * Java Collections Framework</a>. * * @author Doug Lea * @author Josh Bloch * @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 {@code null} if there is no such element. * * @param e the value to match * @return the greatest element less than {@code e}, * or {@code null} 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 {@code null} if there is no such element. * * @param e the value to match * @return the greatest element less than or equal to {@code e}, * or {@code null} 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 {@code null} if there is no such element. * * @param e the value to match * @return the least element greater than or equal to {@code e}, * or {@code null} 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 {@code null} if there is no such element. * * @param e the value to match * @return the least element greater than {@code e}, * or {@code null} 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, * or returns {@code null} if this set is empty. * * @return the first element, or {@code null} if this set is empty */ E pollFirst(); /** * Retrieves and removes the last (highest) element, * or returns {@code null} if this set is empty. * * @return the last element, or {@code null} if this set is empty */ E pollLast(); /** * Returns an iterator over the elements in this set, in ascending order. * * @return an iterator over the elements in this set, in ascending order */ Iterator<E> iterator(); /** * Returns a reverse order view of the elements contained in this set. * The descending set is backed by this set, so changes to the set are * reflected in the descending set, and vice-versa. If either set is * modified while an iteration over either set is in progress (except * through the iterator's own {@code remove} operation), the results of * the iteration are undefined. * * <p>The returned set has an ordering equivalent to * {@link Collections#reverseOrder(Comparator) Collections.reverseOrder}{@code (comparator())}. * The expression {@code s.descendingSet().descendingSet()} returns a * view of {@code s} essentially equivalent to {@code s}. * * @return a reverse order view of this set */ NavigableSet<E> descendingSet(); /** * Returns an iterator over the elements in this set, in descending order. * Equivalent in effect to {@code descendingSet().iterator()}. * * @return an iterator over the elements in this set, in descending order */ Iterator<E> descendingIterator(); /** * Returns a view of the portion of this set whose elements range from * {@code fromElement} to {@code toElement}. If {@code fromElement} and * {@code toElement} are equal, the returned set is empty unless {@code * fromInclusive} and {@code toInclusive} are both true. 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 {@code IllegalArgumentException} * on an attempt to insert an element outside its range. * * @param fromElement low endpoint of the returned set * @param fromInclusive {@code true} if the low endpoint * is to be included in the returned view * @param toElement high endpoint of the returned set * @param toInclusive {@code true} if the high endpoint * is to be included in the returned view * @return a view of the portion of this set whose elements range from * {@code fromElement}, inclusive, to {@code toElement}, exclusive * @throws ClassCastException if {@code fromElement} and * {@code toElement} 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 {@code fromElement} or * {@code toElement} cannot be compared to elements currently in * the set. * @throws NullPointerException if {@code fromElement} or * {@code toElement} is null and this set does * not permit null elements * @throws IllegalArgumentException if {@code fromElement} is * greater than {@code toElement}; or if this set itself * has a restricted range, and {@code fromElement} or * {@code toElement} lies outside the bounds of the range. */ NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive); /** * Returns a view of the portion of this set whose elements are less than * (or equal to, if {@code inclusive} is true) {@code toElement}. 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 {@code IllegalArgumentException} * on an attempt to insert an element outside its range. * * @param toElement high endpoint of the returned set * @param inclusive {@code true} if the high endpoint * is to be included in the returned view * @return a view of the portion of this set whose elements are less than * (or equal to, if {@code inclusive} is true) {@code toElement} * @throws ClassCastException if {@code toElement} is not compatible * with this set's comparator (or, if the set has no comparator, * if {@code toElement} does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if {@code toElement} cannot be compared to elements * currently in the set. * @throws NullPointerException if {@code toElement} is null and * this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and {@code toElement} lies outside the * bounds of the range */ NavigableSet<E> headSet(E toElement, boolean inclusive); /** * Returns a view of the portion of this set whose elements are greater * than (or equal to, if {@code inclusive} is true) {@code fromElement}. * 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 {@code IllegalArgumentException} * on an attempt to insert an element outside its range. * * @param fromElement low endpoint of the returned set * @param inclusive {@code true} if the low endpoint * is to be included in the returned view * @return a view of the portion of this set whose elements are greater * than or equal to {@code fromElement} * @throws ClassCastException if {@code fromElement} is not compatible * with this set's comparator (or, if the set has no comparator, * if {@code fromElement} does not implement {@link Comparable}). * Implementations may, but are not required to, throw this * exception if {@code fromElement} cannot be compared to elements * currently in the set. * @throws NullPointerException if {@code fromElement} is null * and this set does not permit null elements * @throws IllegalArgumentException if this set itself has a * restricted range, and {@code fromElement} lies outside the * bounds of the range */ NavigableSet<E> tailSet(E fromElement, boolean inclusive); /** * {@inheritDoc} * * <p>Equivalent to {@code subSet(fromElement, true, toElement, false)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedSet<E> subSet(E fromElement, E toElement); /** * {@inheritDoc} * * <p>Equivalent to {@code headSet(toElement, false)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedSet<E> headSet(E toElement); /** * {@inheritDoc} * * <p>Equivalent to {@code tailSet(fromElement, true)}. * * @throws ClassCastException {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} */ SortedSet<E> tailSet(E fromElement); }