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416
libjava/classpath/java/util/TreeSet.java
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416
libjava/classpath/java/util/TreeSet.java
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/* TreeSet.java -- a class providing a TreeMap-backed SortedSet
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Copyright (C) 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.io.Serializable;
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/**
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* This class provides a TreeMap-backed implementation of the SortedSet
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* interface. The elements will be sorted according to their <i>natural
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* order</i>, or according to the provided <code>Comparator</code>.<p>
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*
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* Most operations are O(log n), but there is so much overhead that this
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* makes small sets expensive. Note that the ordering must be <i>consistent
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* with equals</i> to correctly implement the Set interface. If this
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* condition is violated, the set is still well-behaved, but you may have
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* suprising results when comparing it to other sets.<p>
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*
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* This implementation is not synchronized. If you need to share this between
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* multiple threads, do something like:<br>
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* <code>SortedSet s
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* = Collections.synchronizedSortedSet(new TreeSet(...));</code><p>
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*
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* The iterators are <i>fail-fast</i>, meaning that any structural
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* modification, except for <code>remove()</code> called on the iterator
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* itself, cause the iterator to throw a
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* <code>ConcurrentModificationException</code> rather than exhibit
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* non-deterministic behavior.
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*
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* @author Jon Zeppieri
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* @author Bryce McKinlay
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* @author Eric Blake (ebb9@email.byu.edu)
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* @see Collection
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* @see Set
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* @see HashSet
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* @see LinkedHashSet
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* @see Comparable
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* @see Comparator
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* @see Collections#synchronizedSortedSet(SortedSet)
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* @see TreeMap
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* @since 1.2
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* @status updated to 1.4
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*/
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public class TreeSet extends AbstractSet
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implements SortedSet, Cloneable, Serializable
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{
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/**
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* Compatible with JDK 1.2.
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*/
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private static final long serialVersionUID = -2479143000061671589L;
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/**
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* The SortedMap which backs this Set.
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*/
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// Not final because of readObject. This will always be one of TreeMap or
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// TreeMap.SubMap, which both extend AbstractMap.
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private transient SortedMap map;
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/**
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* Construct a new TreeSet whose backing TreeMap using the "natural"
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* ordering of keys. Elements that are not mutually comparable will cause
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* ClassCastExceptions down the road.
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*
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* @see Comparable
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*/
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public TreeSet()
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{
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map = new TreeMap();
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}
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/**
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* Construct a new TreeSet whose backing TreeMap uses the supplied
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* Comparator. Elements that are not mutually comparable will cause
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* ClassCastExceptions down the road.
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*
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* @param comparator the Comparator this Set will use
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*/
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public TreeSet(Comparator comparator)
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{
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map = new TreeMap(comparator);
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}
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/**
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* Construct a new TreeSet whose backing TreeMap uses the "natural"
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* orering of the keys and which contains all of the elements in the
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* supplied Collection. This runs in n*log(n) time.
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*
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* @param collection the new Set will be initialized with all
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* of the elements in this Collection
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* @throws ClassCastException if the elements of the collection are not
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* comparable
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* @throws NullPointerException if the collection is null
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* @see Comparable
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*/
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public TreeSet(Collection collection)
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{
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map = new TreeMap();
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addAll(collection);
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}
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/**
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* Construct a new TreeSet, using the same key ordering as the supplied
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* SortedSet and containing all of the elements in the supplied SortedSet.
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* This constructor runs in linear time.
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*
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* @param sortedSet the new TreeSet will use this SortedSet's comparator
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* and will initialize itself with all its elements
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* @throws NullPointerException if sortedSet is null
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*/
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public TreeSet(SortedSet sortedSet)
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{
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map = new TreeMap(sortedSet.comparator());
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Iterator itr = sortedSet.iterator();
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((TreeMap) map).putKeysLinear(itr, sortedSet.size());
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}
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/**
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* This private constructor is used to implement the subSet() calls around
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* a backing TreeMap.SubMap.
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*
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* @param backingMap the submap
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*/
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private TreeSet(SortedMap backingMap)
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{
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map = backingMap;
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}
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/**
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* Adds the spplied Object to the Set if it is not already in the Set;
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* returns true if the element is added, false otherwise.
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*
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* @param obj the Object to be added to this Set
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* @throws ClassCastException if the element cannot be compared with objects
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* already in the set
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*/
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public boolean add(Object obj)
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{
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return map.put(obj, "") == null;
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}
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/**
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* Adds all of the elements in the supplied Collection to this TreeSet.
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*
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* @param c The collection to add
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* @return true if the Set is altered, false otherwise
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* @throws NullPointerException if c is null
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* @throws ClassCastException if an element in c cannot be compared with
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* objects already in the set
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*/
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public boolean addAll(Collection c)
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{
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boolean result = false;
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int pos = c.size();
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Iterator itr = c.iterator();
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while (--pos >= 0)
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result |= (map.put(itr.next(), "") == null);
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return result;
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}
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/**
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* Removes all elements in this Set.
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*/
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public void clear()
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{
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map.clear();
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}
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/**
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* Returns a shallow copy of this Set. The elements are not cloned.
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*
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* @return the cloned set
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*/
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public Object clone()
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{
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TreeSet copy = null;
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try
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{
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copy = (TreeSet) super.clone();
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// Map may be either TreeMap or TreeMap.SubMap, hence the ugly casts.
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copy.map = (SortedMap) ((AbstractMap) map).clone();
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}
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catch (CloneNotSupportedException x)
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{
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// Impossible result.
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}
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return copy;
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}
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/**
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* Returns this Set's comparator.
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*
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* @return the comparator, or null if the set uses natural ordering
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*/
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public Comparator comparator()
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{
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return map.comparator();
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}
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/**
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* Returns true if this Set contains the supplied Object, false otherwise.
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*
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* @param obj the Object to check for
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* @return true if it is in the set
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* @throws ClassCastException if obj cannot be compared with objects
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* already in the set
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*/
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public boolean contains(Object obj)
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{
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return map.containsKey(obj);
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}
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/**
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* Returns the first (by order) element in this Set.
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*
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* @return the first element
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* @throws NoSuchElementException if the set is empty
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*/
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public Object first()
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{
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return map.firstKey();
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}
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/**
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* Returns a view of this Set including all elements less than
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* <code>to</code>. The returned set is backed by the original, so changes
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* in one appear in the other. The subset will throw an
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* {@link IllegalArgumentException} for any attempt to access or add an
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* element beyond the specified cutoff. The returned set does not include
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* the endpoint; if you want inclusion, pass the successor element.
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*
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* @param to the (exclusive) cutoff point
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* @return a view of the set less than the cutoff
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* @throws ClassCastException if <code>to</code> is not compatible with
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* the comparator (or is not Comparable, for natural ordering)
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* @throws NullPointerException if to is null, but the comparator does not
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* tolerate null elements
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*/
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public SortedSet headSet(Object to)
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{
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return new TreeSet(map.headMap(to));
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}
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/**
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* Returns true if this Set has size 0, false otherwise.
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*
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* @return true if the set is empty
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*/
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public boolean isEmpty()
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{
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return map.isEmpty();
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}
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/**
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* Returns in Iterator over the elements in this TreeSet, which traverses
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* in ascending order.
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*
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* @return an iterator
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*/
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public Iterator iterator()
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{
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return map.keySet().iterator();
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}
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/**
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* Returns the last (by order) element in this Set.
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*
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* @return the last element
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* @throws NoSuchElementException if the set is empty
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*/
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public Object last()
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{
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return map.lastKey();
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}
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/**
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* If the supplied Object is in this Set, it is removed, and true is
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* returned; otherwise, false is returned.
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*
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* @param obj the Object to remove from this Set
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* @return true if the set was modified
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* @throws ClassCastException if obj cannot be compared to set elements
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*/
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public boolean remove(Object obj)
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{
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return map.remove(obj) != null;
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}
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/**
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* Returns the number of elements in this Set
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*
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* @return the set size
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*/
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public int size()
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{
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return map.size();
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}
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/**
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* Returns a view of this Set including all elements greater or equal to
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* <code>from</code> and less than <code>to</code> (a half-open interval).
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* The returned set is backed by the original, so changes in one appear in
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* the other. The subset will throw an {@link IllegalArgumentException}
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* for any attempt to access or add an element beyond the specified cutoffs.
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* The returned set includes the low endpoint but not the high; if you want
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* to reverse this behavior on either end, pass in the successor element.
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*
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* @param from the (inclusive) low cutoff point
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* @param to the (exclusive) high cutoff point
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* @return a view of the set between the cutoffs
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* @throws ClassCastException if either cutoff is not compatible with
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* the comparator (or is not Comparable, for natural ordering)
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* @throws NullPointerException if from or to is null, but the comparator
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* does not tolerate null elements
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* @throws IllegalArgumentException if from is greater than to
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*/
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public SortedSet subSet(Object from, Object to)
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{
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return new TreeSet(map.subMap(from, to));
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}
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/**
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* Returns a view of this Set including all elements greater or equal to
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* <code>from</code>. The returned set is backed by the original, so
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* changes in one appear in the other. The subset will throw an
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* {@link IllegalArgumentException} for any attempt to access or add an
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* element beyond the specified cutoff. The returned set includes the
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* endpoint; if you want to exclude it, pass in the successor element.
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*
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* @param from the (inclusive) low cutoff point
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* @return a view of the set above the cutoff
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* @throws ClassCastException if <code>from</code> is not compatible with
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* the comparator (or is not Comparable, for natural ordering)
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* @throws NullPointerException if from is null, but the comparator
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* does not tolerate null elements
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*/
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public SortedSet tailSet(Object from)
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{
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return new TreeSet(map.tailMap(from));
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}
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/**
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* Serializes this object to the given stream.
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*
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* @param s the stream to write to
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* @throws IOException if the underlying stream fails
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* @serialData the <i>comparator</i> (Object), followed by the set size
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* (int), the the elements in sorted order (Object)
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*/
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private void writeObject(ObjectOutputStream s) throws IOException
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{
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s.defaultWriteObject();
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Iterator itr = map.keySet().iterator();
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int pos = map.size();
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s.writeObject(map.comparator());
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s.writeInt(pos);
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while (--pos >= 0)
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s.writeObject(itr.next());
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}
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/**
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* Deserializes this object from the given stream.
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*
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* @param s the stream to read from
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* @throws ClassNotFoundException if the underlying stream fails
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* @throws IOException if the underlying stream fails
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* @serialData the <i>comparator</i> (Object), followed by the set size
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* (int), the the elements in sorted order (Object)
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*/
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private void readObject(ObjectInputStream s)
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throws IOException, ClassNotFoundException
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{
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s.defaultReadObject();
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Comparator comparator = (Comparator) s.readObject();
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int size = s.readInt();
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map = new TreeMap(comparator);
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((TreeMap) map).putFromObjStream(s, size, false);
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}
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}
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