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Comparing jsr166/src/main/java/util/TreeSet.java (file contents):
Revision 1.17 by jsr166, Fri Jun 24 20:44:49 2005 UTC vs.
Revision 1.27 by jsr166, Sun May 18 23:47:56 2008 UTC

# Line 1 | Line 1
1   /*
2 < * %W% %E%
2 > * Copyright 1998-2006 Sun Microsystems, Inc.  All Rights Reserved.
3 > * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4   *
5 < * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
6 < * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
5 > * This code is free software; you can redistribute it and/or modify it
6 > * under the terms of the GNU General Public License version 2 only, as
7 > * published by the Free Software Foundation.  Sun designates this
8 > * particular file as subject to the "Classpath" exception as provided
9 > * by Sun in the LICENSE file that accompanied this code.
10 > *
11 > * This code is distributed in the hope that it will be useful, but WITHOUT
12 > * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 > * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 > * version 2 for more details (a copy is included in the LICENSE file that
15 > * accompanied this code).
16 > *
17 > * You should have received a copy of the GNU General Public License version
18 > * 2 along with this work; if not, write to the Free Software Foundation,
19 > * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 > *
21 > * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 > * CA 95054 USA or visit www.sun.com if you need additional information or
23 > * have any questions.
24   */
25  
26   package java.util;
9 import java.util.*; // for javadoc (till 6280605 is fixed)
27  
28   /**
29   * A {@link NavigableSet} implementation based on a {@link TreeMap}.
# Line 15 | Line 32 | import java.util.*; // for javadoc (till
32   * time, depending on which constructor is used.
33   *
34   * <p>This implementation provides guaranteed log(n) time cost for the basic
35 < * operations (<tt>add</tt>, <tt>remove</tt> and <tt>contains</tt>).
35 > * operations ({@code add}, {@code remove} and {@code contains}).
36   *
37   * <p>Note that the ordering maintained by a set (whether or not an explicit
38   * comparator is provided) must be <i>consistent with equals</i> if it is to
39 < * correctly implement the <tt>Set</tt> interface.  (See <tt>Comparable</tt>
40 < * or <tt>Comparator</tt> for a precise definition of <i>consistent with
41 < * equals</i>.)  This is so because the <tt>Set</tt> interface is defined in
42 < * terms of the <tt>equals</tt> operation, but a <tt>TreeSet</tt> instance
43 < * performs all element comparisons using its <tt>compareTo</tt> (or
44 < * <tt>compare</tt>) method, so two elements that are deemed equal by this method
39 > * correctly implement the {@code Set} interface.  (See {@code Comparable}
40 > * or {@code Comparator} for a precise definition of <i>consistent with
41 > * equals</i>.)  This is so because the {@code Set} interface is defined in
42 > * terms of the {@code equals} operation, but a {@code TreeSet} instance
43 > * performs all element comparisons using its {@code compareTo} (or
44 > * {@code compare}) method, so two elements that are deemed equal by this method
45   * are, from the standpoint of the set, equal.  The behavior of a set
46   * <i>is</i> well-defined even if its ordering is inconsistent with equals; it
47 < * just fails to obey the general contract of the <tt>Set</tt> interface.
47 > * just fails to obey the general contract of the {@code Set} interface.
48   *
49 < * <p><b>Note that this implementation is not synchronized.</b> If multiple
50 < * threads access a set concurrently, and at least one of the threads modifies
51 < * the set, it <i>must</i> be synchronized externally.  This is typically
52 < * accomplished by synchronizing on some object that naturally encapsulates
53 < * the set.  If no such object exists, the set should be "wrapped" using the
54 < * <tt>Collections.synchronizedSet</tt> method.  This is best done at creation
55 < * time, to prevent accidental unsynchronized access to the set: <pre>
56 < *     SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));
57 < * </pre>
49 > * <p><strong>Note that this implementation is not synchronized.</strong>
50 > * If multiple threads access a tree set concurrently, and at least one
51 > * of the threads modifies the set, it <i>must</i> be synchronized
52 > * externally.  This is typically accomplished by synchronizing on some
53 > * object that naturally encapsulates the set.
54 > * If no such object exists, the set should be "wrapped" using the
55 > * {@link Collections#synchronizedSortedSet Collections.synchronizedSortedSet}
56 > * method.  This is best done at creation time, to prevent accidental
57 > * unsynchronized access to the set: <pre>
58 > *   SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
59   *
60 < * <p>The iterators returned by this class's <tt>iterator</tt> method are
60 > * <p>The iterators returned by this class's {@code iterator} method are
61   * <i>fail-fast</i>: if the set is modified at any time after the iterator is
62 < * created, in any way except through the iterator's own <tt>remove</tt>
62 > * created, in any way except through the iterator's own {@code remove}
63   * method, the iterator will throw a {@link ConcurrentModificationException}.
64   * Thus, in the face of concurrent modification, the iterator fails quickly
65   * and cleanly, rather than risking arbitrary, non-deterministic behavior at
# Line 50 | Line 68 | import java.util.*; // for javadoc (till
68   * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
69   * as it is, generally speaking, impossible to make any hard guarantees in the
70   * presence of unsynchronized concurrent modification.  Fail-fast iterators
71 < * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
71 > * throw {@code ConcurrentModificationException} on a best-effort basis.
72   * Therefore, it would be wrong to write a program that depended on this
73   * exception for its correctness:   <i>the fail-fast behavior of iterators
74   * should be used only to detect bugs.</i>
75   *
76   * <p>This class is a member of the
77 < * <a href="{@docRoot}/../guide/collections/index.html">
77 > * <a href="{@docRoot}/../technotes/guides/collections/index.html">
78   * Java Collections Framework</a>.
79   *
80   * @param <E> the type of elements maintained by this set
81   *
82   * @author  Josh Bloch
83   * @version %I%, %G%
84 < * @see     Collection
85 < * @see     Set
86 < * @see     HashSet
84 > * @see     Collection
85 > * @see     Set
86 > * @see     HashSet
87   * @see     Comparable
88   * @see     Comparator
89 < * @see     Collections#synchronizedSortedSet(SortedSet)
72 < * @see     TreeMap
89 > * @see     TreeMap
90   * @since   1.2
91   */
92  
93 < public class TreeSet<E>
77 <    extends AbstractSet<E>
93 > public class TreeSet<E> extends AbstractSet<E>
94      implements NavigableSet<E>, Cloneable, java.io.Serializable
95   {
96 <    private transient NavigableMap<E,Object> m; // The backing Map
96 >    /**
97 >     * The backing map.
98 >     */
99 >    private transient NavigableMap<E,Object> m;
100  
101      // Dummy value to associate with an Object in the backing Map
102      private static final Object PRESENT = new Object();
# Line 85 | Line 104 | public class TreeSet<E>
104      /**
105       * Constructs a set backed by the specified navigable map.
106       */
107 <    private TreeSet(NavigableMap<E,Object> m) {
107 >    TreeSet(NavigableMap<E,Object> m) {
108          this.m = m;
109      }
110  
# Line 94 | Line 113 | public class TreeSet<E>
113       * natural ordering of its elements.  All elements inserted into
114       * the set must implement the {@link Comparable} interface.
115       * Furthermore, all such elements must be <i>mutually
116 <     * comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a
117 <     * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
118 <     * <tt>e2</tt> in the set.  If the user attempts to add an element
116 >     * comparable</i>: {@code e1.compareTo(e2)} must not throw a
117 >     * {@code ClassCastException} for any elements {@code e1} and
118 >     * {@code e2} in the set.  If the user attempts to add an element
119       * to the set that violates this constraint (for example, the user
120       * attempts to add a string element to a set whose elements are
121 <     * integers), the <tt>add(Object)</tt> call will throw a
122 <     * <tt>ClassCastException</tt>.
121 >     * integers), the {@code add} call will throw a
122 >     * {@code ClassCastException}.
123       */
124      public TreeSet() {
125 <        this(new TreeMap<E,Object>());
125 >        this(new TreeMap<E,Object>());
126      }
127  
128      /**
129       * Constructs a new, empty tree set, sorted according to the specified
130       * comparator.  All elements inserted into the set must be <i>mutually
131 <     * comparable</i> by the specified comparator: <tt>comparator.compare(e1,
132 <     * e2)</tt> must not throw a <tt>ClassCastException</tt> for any elements
133 <     * <tt>e1</tt> and <tt>e2</tt> in the set.  If the user attempts to add
131 >     * comparable</i> by the specified comparator: {@code comparator.compare(e1,
132 >     * e2)} must not throw a {@code ClassCastException} for any elements
133 >     * {@code e1} and {@code e2} in the set.  If the user attempts to add
134       * an element to the set that violates this constraint, the
135 <     * <tt>add(Object)</tt> call will throw a <tt>ClassCastException</tt>.
135 >     * {@code add} call will throw a {@code ClassCastException}.
136       *
137       * @param comparator the comparator that will be used to order this set.
138 <     *        If <tt>null</tt>, the {@linkplain Comparable natural
138 >     *        If {@code null}, the {@linkplain Comparable natural
139       *        ordering} of the elements will be used.
140       */
141      public TreeSet(Comparator<? super E> comparator) {
142 <        this(new TreeMap<E,Object>(comparator));
142 >        this(new TreeMap<E,Object>(comparator));
143      }
144  
145      /**
# Line 128 | Line 147 | public class TreeSet<E>
147       * collection, sorted according to the <i>natural ordering</i> of its
148       * elements.  All elements inserted into the set must implement the
149       * {@link Comparable} interface.  Furthermore, all such elements must be
150 <     * <i>mutually comparable</i>: <tt>e1.compareTo(e2)</tt> must not throw a
151 <     * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
152 <     * <tt>e2</tt> in the set.
150 >     * <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
151 >     * {@code ClassCastException} for any elements {@code e1} and
152 >     * {@code e2} in the set.
153       *
154       * @param c collection whose elements will comprise the new set
155 <     * @throws ClassCastException if the elements in <tt>c</tt> are
155 >     * @throws ClassCastException if the elements in {@code c} are
156       *         not {@link Comparable}, or are not mutually comparable
157       * @throws NullPointerException if the specified collection is null
158       */
# Line 151 | Line 170 | public class TreeSet<E>
170       */
171      public TreeSet(SortedSet<E> s) {
172          this(s.comparator());
173 <        addAll(s);
173 >        addAll(s);
174      }
175  
176      /**
# Line 160 | Line 179 | public class TreeSet<E>
179       * @return an iterator over the elements in this set in ascending order
180       */
181      public Iterator<E> iterator() {
182 <        return m.keySet().iterator();
182 >        return m.navigableKeySet().iterator();
183      }
184  
185      /**
# Line 170 | Line 189 | public class TreeSet<E>
189       * @since 1.6
190       */
191      public Iterator<E> descendingIterator() {
192 <        return m.descendingKeySet().iterator();
192 >        return m.descendingKeySet().iterator();
193 >    }
194 >
195 >    /**
196 >     * @since 1.6
197 >     */
198 >    public NavigableSet<E> descendingSet() {
199 >        return new TreeSet(m.descendingMap());
200      }
201  
202      /**
# Line 179 | Line 205 | public class TreeSet<E>
205       * @return the number of elements in this set (its cardinality)
206       */
207      public int size() {
208 <        return m.size();
208 >        return m.size();
209      }
210  
211      /**
212 <     * Returns <tt>true</tt> if this set contains no elements.
212 >     * Returns {@code true} if this set contains no elements.
213       *
214 <     * @return <tt>true</tt> if this set contains no elements
214 >     * @return {@code true} if this set contains no elements
215       */
216      public boolean isEmpty() {
217 <        return m.isEmpty();
217 >        return m.isEmpty();
218      }
219  
220      /**
221 <     * Returns <tt>true</tt> if this set contains the specified element.
222 <     * More formally, returns <tt>true</tt> if and only if this set
223 <     * contains an element <tt>e</tt> such that
221 >     * Returns {@code true} if this set contains the specified element.
222 >     * More formally, returns {@code true} if and only if this set
223 >     * contains an element {@code e} such that
224       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
225       *
226       * @param o object to be checked for containment in this set
227 <     * @return <tt>true</tt> if this set contains the specified element
227 >     * @return {@code true} if this set contains the specified element
228       * @throws ClassCastException if the specified object cannot be compared
229       *         with the elements currently in the set
230       * @throws NullPointerException if the specified element is null
# Line 206 | Line 232 | public class TreeSet<E>
232       *         does not permit null elements
233       */
234      public boolean contains(Object o) {
235 <        return m.containsKey(o);
235 >        return m.containsKey(o);
236      }
237  
238      /**
239       * Adds the specified element to this set if it is not already present.
240 <     * More formally, adds the specified element <tt>e</tt> to this set if
241 <     * the set contains no element <tt>e2</tt> such that
240 >     * More formally, adds the specified element {@code e} to this set if
241 >     * the set contains no element {@code e2} such that
242       * <tt>(e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))</tt>.
243       * If this set already contains the element, the call leaves the set
244 <     * unchanged and returns <tt>false</tt>.
244 >     * unchanged and returns {@code false}.
245       *
246       * @param e element to be added to this set
247 <     * @return <tt>true</tt> if this set did not already contain the specified
247 >     * @return {@code true} if this set did not already contain the specified
248       *         element
249       * @throws ClassCastException if the specified object cannot be compared
250       *         with the elements currently in this set
# Line 227 | Line 253 | public class TreeSet<E>
253       *         does not permit null elements
254       */
255      public boolean add(E e) {
256 <        return m.put(e, PRESENT)==null;
256 >        return m.put(e, PRESENT)==null;
257      }
258  
259      /**
260       * Removes the specified element from this set if it is present.
261 <     * More formally, removes an element <tt>e</tt> such that
261 >     * More formally, removes an element {@code e} such that
262       * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>,
263 <     * if this set contains such an element.  Returns <tt>true</tt> if
263 >     * if this set contains such an element.  Returns {@code true} if
264       * this set contained the element (or equivalently, if this set
265       * changed as a result of the call).  (This set will not contain the
266       * element once the call returns.)
267       *
268       * @param o object to be removed from this set, if present
269 <     * @return <tt>true</tt> if this set contained the specified element
269 >     * @return {@code true} if this set contained the specified element
270       * @throws ClassCastException if the specified object cannot be compared
271       *         with the elements currently in this set
272       * @throws NullPointerException if the specified element is null
# Line 248 | Line 274 | public class TreeSet<E>
274       *         does not permit null elements
275       */
276      public boolean remove(Object o) {
277 <        return m.remove(o)==PRESENT;
277 >        return m.remove(o)==PRESENT;
278      }
279  
280      /**
# Line 256 | Line 282 | public class TreeSet<E>
282       * The set will be empty after this call returns.
283       */
284      public void clear() {
285 <        m.clear();
285 >        m.clear();
286      }
287  
288      /**
289       * Adds all of the elements in the specified collection to this set.
290       *
291       * @param c collection containing elements to be added to this set
292 <     * @return <tt>true</tt> if this set changed as a result of the call
292 >     * @return {@code true} if this set changed as a result of the call
293       * @throws ClassCastException if the elements provided cannot be compared
294       *         with the elements currently in the set
295       * @throws NullPointerException if the specified collection is null or
# Line 273 | Line 299 | public class TreeSet<E>
299      public  boolean addAll(Collection<? extends E> c) {
300          // Use linear-time version if applicable
301          if (m.size()==0 && c.size() > 0 &&
302 <            c instanceof SortedSet &&
302 >            c instanceof SortedSet &&
303              m instanceof TreeMap) {
304              SortedSet<? extends E> set = (SortedSet<? extends E>) c;
305              TreeMap<E,Object> map = (TreeMap<E, Object>) m;
# Line 289 | Line 315 | public class TreeSet<E>
315  
316      /**
317       * @throws ClassCastException {@inheritDoc}
318 <     * @throws NullPointerException if <tt>fromElement</tt> or
319 <     *         <tt>toElement</tt> is null and this set uses natural ordering,
320 <     *         or its comparator does not permit null elements
318 >     * @throws NullPointerException if {@code fromElement} or {@code toElement}
319 >     *         is null and this set uses natural ordering, or its comparator
320 >     *         does not permit null elements
321       * @throws IllegalArgumentException {@inheritDoc}
322       * @since 1.6
323       */
324 <    public NavigableSet<E> navigableSubSet(E fromElement, E toElement) {
325 <        return new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
324 >    public NavigableSet<E> subSet(E fromElement, boolean fromInclusive,
325 >                                  E toElement,   boolean toInclusive) {
326 >        return new TreeSet<E>(m.subMap(fromElement, fromInclusive,
327 >                                       toElement,   toInclusive));
328      }
329  
330      /**
331       * @throws ClassCastException {@inheritDoc}
332 <     * @throws NullPointerException if <tt>toElement</tt> is null and
332 >     * @throws NullPointerException if {@code toElement} is null and
333       *         this set uses natural ordering, or its comparator does
334       *         not permit null elements
335       * @throws IllegalArgumentException {@inheritDoc}
336       * @since 1.6
337       */
338 <    public NavigableSet<E> navigableHeadSet(E toElement) {
339 <        return new TreeSet<E>(m.navigableHeadMap(toElement));
338 >    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
339 >        return new TreeSet<E>(m.headMap(toElement, inclusive));
340      }
341  
342      /**
343       * @throws ClassCastException {@inheritDoc}
344 <     * @throws NullPointerException if <tt>fromElement</tt> is null and
344 >     * @throws NullPointerException if {@code fromElement} is null and
345       *         this set uses natural ordering, or its comparator does
346       *         not permit null elements
347       * @throws IllegalArgumentException {@inheritDoc}
348       * @since 1.6
349       */
350 <    public NavigableSet<E> navigableTailSet(E fromElement) {
351 <        return new TreeSet<E>(m.navigableTailMap(fromElement));
350 >    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
351 >        return new TreeSet<E>(m.tailMap(fromElement, inclusive));
352      }
353  
354      /**
327     * Equivalent to {@link #navigableSubSet} but with a return type
328     * conforming to the <tt>SortedSet</tt> interface.
329     *
330     * <p>{@inheritDoc}
331     *
355       * @throws ClassCastException {@inheritDoc}
356 <     * @throws NullPointerException if <tt>fromElement</tt> or
357 <     *         <tt>toElement</tt> is null and this set uses natural ordering,
356 >     * @throws NullPointerException if {@code fromElement} or
357 >     *         {@code toElement} is null and this set uses natural ordering,
358       *         or its comparator does not permit null elements
359       * @throws IllegalArgumentException {@inheritDoc}
360       */
361      public SortedSet<E> subSet(E fromElement, E toElement) {
362 <        return new TreeSet<E>(m.navigableSubMap(fromElement, toElement));
362 >        return subSet(fromElement, true, toElement, false);
363      }
364  
365      /**
343     * Equivalent to {@link #navigableHeadSet} but with a return type
344     * conforming to the <tt>SortedSet</tt> interface.
345     *
346     * <p>{@inheritDoc}
347     *
366       * @throws ClassCastException {@inheritDoc}
367 <     * @throws NullPointerException if <tt>toElement</tt> is null
367 >     * @throws NullPointerException if {@code toElement} is null
368       *         and this set uses natural ordering, or its comparator does
369       *         not permit null elements
370       * @throws IllegalArgumentException {@inheritDoc}
371       */
372      public SortedSet<E> headSet(E toElement) {
373 <        return new TreeSet<E>(m.navigableHeadMap(toElement));
373 >        return headSet(toElement, false);
374      }
375  
376      /**
359     * Equivalent to {@link #navigableTailSet} but with a return type
360     * conforming to the <tt>SortedSet</tt> interface.
361     *
362     * <p>{@inheritDoc}
363     *
377       * @throws ClassCastException {@inheritDoc}
378 <     * @throws NullPointerException if <tt>fromElement</tt> is null
378 >     * @throws NullPointerException if {@code fromElement} is null
379       *         and this set uses natural ordering, or its comparator does
380       *         not permit null elements
381       * @throws IllegalArgumentException {@inheritDoc}
382       */
383      public SortedSet<E> tailSet(E fromElement) {
384 <        return new TreeSet<E>(m.navigableTailMap(fromElement));
384 >        return tailSet(fromElement, true);
385      }
386  
387      public Comparator<? super E> comparator() {
# Line 452 | Line 465 | public class TreeSet<E>
465      }
466  
467      /**
468 <     * Returns a shallow copy of this <tt>TreeSet</tt> instance. (The elements
468 >     * Returns a shallow copy of this {@code TreeSet} instance. (The elements
469       * themselves are not cloned.)
470       *
471       * @return a shallow copy of this set
472       */
473      public Object clone() {
474          TreeSet<E> clone = null;
475 <        try {
476 <            clone = (TreeSet<E>) super.clone();
477 <        } catch (CloneNotSupportedException e) {
478 <            throw new InternalError();
479 <        }
475 >        try {
476 >            clone = (TreeSet<E>) super.clone();
477 >        } catch (CloneNotSupportedException e) {
478 >            throw new InternalError();
479 >        }
480  
481          clone.m = new TreeMap<E,Object>(m);
469
482          return clone;
483      }
484  
485      /**
486 <     * Save the state of the <tt>TreeSet</tt> instance to a stream (that is,
486 >     * Save the state of the {@code TreeSet} instance to a stream (that is,
487       * serialize it).
488       *
489       * @serialData Emits the comparator used to order this set, or
490 <     *             <tt>null</tt> if it obeys its elements' natural ordering
490 >     *             {@code null} if it obeys its elements' natural ordering
491       *             (Object), followed by the size of the set (the number of
492       *             elements it contains) (int), followed by all of its
493       *             elements (each an Object) in order (as determined by the
# Line 484 | Line 496 | public class TreeSet<E>
496       */
497      private void writeObject(java.io.ObjectOutputStream s)
498          throws java.io.IOException {
499 <        // Write out any hidden stuff
500 <        s.defaultWriteObject();
499 >        // Write out any hidden stuff
500 >        s.defaultWriteObject();
501  
502          // Write out Comparator
503          s.writeObject(m.comparator());
# Line 493 | Line 505 | public class TreeSet<E>
505          // Write out size
506          s.writeInt(m.size());
507  
508 <        // Write out all elements in the proper order.
509 <        for (Iterator i=m.keySet().iterator(); i.hasNext(); )
508 >        // Write out all elements in the proper order.
509 >        for (Iterator i=m.keySet().iterator(); i.hasNext(); )
510              s.writeObject(i.next());
511      }
512  
513      /**
514 <     * Reconstitute the <tt>TreeSet</tt> instance from a stream (that is,
514 >     * Reconstitute the {@code TreeSet} instance from a stream (that is,
515       * deserialize it).
516       */
517      private void readObject(java.io.ObjectInputStream s)
518          throws java.io.IOException, ClassNotFoundException {
519 <        // Read in any hidden stuff
520 <        s.defaultReadObject();
519 >        // Read in any hidden stuff
520 >        s.defaultReadObject();
521  
522          // Read in Comparator
523          Comparator<? super E> c = (Comparator<? super E>) s.readObject();
524  
525          // Create backing TreeMap
526 <        TreeMap<E,Object> tm;
527 <        if (c==null)
528 <            tm = new TreeMap<E,Object>();
529 <        else
530 <            tm = new TreeMap<E,Object>(c);
531 <        m = tm;
526 >        TreeMap<E,Object> tm;
527 >        if (c==null)
528 >            tm = new TreeMap<E,Object>();
529 >        else
530 >            tm = new TreeMap<E,Object>(c);
531 >        m = tm;
532  
533          // Read in size
534          int size = s.readInt();

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