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My first initial commit with all of mine experimental changes.

Dmitry Kabak (userdima committed 13 years ago

Commit d37b88d1 parent 3f5b46618352 files · +2598093 −-8690Browse files

Showing the changes to java/pkg/java/util/HashSet.java (1 of 18352 files). Show all

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1+/*
2+ * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
3+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4+ *
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. Oracle designates this
8+ * particular file as subject to the "Classpath" exception as provided
9+ * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22+ * or visit www.oracle.com if you need additional information or have any
23+ * questions.
24+ */
25+
26+package java.util;
27+
28+/**
29+ * This class implements the <tt>Set</tt> interface, backed by a hash table
30+ * (actually a <tt>HashMap</tt> instance). It makes no guarantees as to the
31+ * iteration order of the set; in particular, it does not guarantee that the
32+ * order will remain constant over time. This class permits the <tt>null</tt>
33+ * element.
34+ *
35+ * <p>This class offers constant time performance for the basic operations
36+ * (<tt>add</tt>, <tt>remove</tt>, <tt>contains</tt> and <tt>size</tt>),
37+ * assuming the hash function disperses the elements properly among the
38+ * buckets. Iterating over this set requires time proportional to the sum of
39+ * the <tt>HashSet</tt> instance's size (the number of elements) plus the
40+ * "capacity" of the backing <tt>HashMap</tt> instance (the number of
41+ * buckets). Thus, it's very important not to set the initial capacity too
42+ * high (or the load factor too low) if iteration performance is important.
43+ *
44+ * <p><strong>Note that this implementation is not synchronized.</strong>
45+ * If multiple threads access a hash set concurrently, and at least one of
46+ * the threads modifies the set, it <i>must</i> be synchronized externally.
47+ * This is typically accomplished by synchronizing on some object that
48+ * naturally encapsulates the set.
49+ *
50+ * If no such object exists, the set should be "wrapped" using the
51+ * {@link Collections#synchronizedSet Collections.synchronizedSet}
52+ * method. This is best done at creation time, to prevent accidental
53+ * unsynchronized access to the set:<pre>
54+ * Set s = Collections.synchronizedSet(new HashSet(...));</pre>
55+ *
56+ * <p>The iterators returned by this class's <tt>iterator</tt> method are
57+ * <i>fail-fast</i>: if the set is modified at any time after the iterator is
58+ * created, in any way except through the iterator's own <tt>remove</tt>
59+ * method, the Iterator throws a {@link ConcurrentModificationException}.
60+ * Thus, in the face of concurrent modification, the iterator fails quickly
61+ * and cleanly, rather than risking arbitrary, non-deterministic behavior at
62+ * an undetermined time in the future.
63+ *
64+ * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
65+ * as it is, generally speaking, impossible to make any hard guarantees in the
66+ * presence of unsynchronized concurrent modification. Fail-fast iterators
67+ * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
68+ * Therefore, it would be wrong to write a program that depended on this
69+ * exception for its correctness: <i>the fail-fast behavior of iterators
70+ * should be used only to detect bugs.</i>
71+ *
72+ * <p>This class is a member of the
73+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
74+ * Java Collections Framework</a>.
75+ *
76+ * @param <E> the type of elements maintained by this set
77+ *
78+ * @author Josh Bloch
79+ * @author Neal Gafter
80+ * @see Collection
81+ * @see Set
82+ * @see TreeSet
83+ * @see HashMap
84+ * @since 1.2
85+ */
86+
87+public class HashSet<E>
88+ extends AbstractSet<E>
89+ implements Set<E>, Cloneable, java.io.Serializable
90+{
91+ static final long serialVersionUID = -5024744406713321676L;
92+
93+ private transient HashMap<E,Object> map;
94+
95+ // Dummy value to associate with an Object in the backing Map
96+ private static final Object PRESENT = new Object();
97+
98+ /**
99+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
100+ * default initial capacity (16) and load factor (0.75).
101+ */
102+ public HashSet() {
103+ map = new HashMap<>();
104+ }
105+
106+ /**
107+ * Constructs a new set containing the elements in the specified
108+ * collection. The <tt>HashMap</tt> is created with default load factor
109+ * (0.75) and an initial capacity sufficient to contain the elements in
110+ * the specified collection.
111+ *
112+ * @param c the collection whose elements are to be placed into this set
113+ * @throws NullPointerException if the specified collection is null
114+ */
115+ public HashSet(Collection<? extends E> c) {
116+ map = new HashMap<>(Math.max((int) (c.size()/.75f) + 1, 16));
117+ addAll(c);
118+ }
119+
120+ /**
121+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
122+ * the specified initial capacity and the specified load factor.
123+ *
124+ * @param initialCapacity the initial capacity of the hash map
125+ * @param loadFactor the load factor of the hash map
126+ * @throws IllegalArgumentException if the initial capacity is less
127+ * than zero, or if the load factor is nonpositive
128+ */
129+ public HashSet(int initialCapacity, float loadFactor) {
130+ map = new HashMap<>(initialCapacity, loadFactor);
131+ }
132+
133+ /**
134+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
135+ * the specified initial capacity and default load factor (0.75).
136+ *
137+ * @param initialCapacity the initial capacity of the hash table
138+ * @throws IllegalArgumentException if the initial capacity is less
139+ * than zero
140+ */
141+ public HashSet(int initialCapacity) {
142+ map = new HashMap<>(initialCapacity);
143+ }
144+
145+ /**
146+ * Constructs a new, empty linked hash set. (This package private
147+ * constructor is only used by LinkedHashSet.) The backing
148+ * HashMap instance is a LinkedHashMap with the specified initial
149+ * capacity and the specified load factor.
150+ *
151+ * @param initialCapacity the initial capacity of the hash map
152+ * @param loadFactor the load factor of the hash map
153+ * @param dummy ignored (distinguishes this
154+ * constructor from other int, float constructor.)
155+ * @throws IllegalArgumentException if the initial capacity is less
156+ * than zero, or if the load factor is nonpositive
157+ */
158+ HashSet(int initialCapacity, float loadFactor, boolean dummy) {
159+ map = new LinkedHashMap<>(initialCapacity, loadFactor);
160+ }
161+
162+ /**
163+ * Returns an iterator over the elements in this set. The elements
164+ * are returned in no particular order.
165+ *
166+ * @return an Iterator over the elements in this set
167+ * @see ConcurrentModificationException
168+ */
169+ public Iterator<E> iterator() {
170+ return map.keySet().iterator();
171+ }
172+
173+ /**
174+ * Returns the number of elements in this set (its cardinality).
175+ *
176+ * @return the number of elements in this set (its cardinality)
177+ */
178+ public int size() {
179+ return map.size();
180+ }
181+
182+ /**
183+ * Returns <tt>true</tt> if this set contains no elements.
184+ *
185+ * @return <tt>true</tt> if this set contains no elements
186+ */
187+ public boolean isEmpty() {
188+ return map.isEmpty();
189+ }
190+
191+ /**
192+ * Returns <tt>true</tt> if this set contains the specified element.
193+ * More formally, returns <tt>true</tt> if and only if this set
194+ * contains an element <tt>e</tt> such that
195+ * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
196+ *
197+ * @param o element whose presence in this set is to be tested
198+ * @return <tt>true</tt> if this set contains the specified element
199+ */
200+ public boolean contains(Object o) {
201+ return map.containsKey(o);
202+ }
203+
204+ /**
205+ * Adds the specified element to this set if it is not already present.
206+ * More formally, adds the specified element <tt>e</tt> to this set if
207+ * this set contains no element <tt>e2</tt> such that
208+ * <tt>(e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))</tt>.
209+ * If this set already contains the element, the call leaves the set
210+ * unchanged and returns <tt>false</tt>.
211+ *
212+ * @param e element to be added to this set
213+ * @return <tt>true</tt> if this set did not already contain the specified
214+ * element
215+ */
216+ public boolean add(E e) {
217+ return map.put(e, PRESENT)==null;
218+ }
219+
220+ /**
221+ * Removes the specified element from this set if it is present.
222+ * More formally, removes an element <tt>e</tt> such that
223+ * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>,
224+ * if this set contains such an element. Returns <tt>true</tt> if
225+ * this set contained the element (or equivalently, if this set
226+ * changed as a result of the call). (This set will not contain the
227+ * element once the call returns.)
228+ *
229+ * @param o object to be removed from this set, if present
230+ * @return <tt>true</tt> if the set contained the specified element
231+ */
232+ public boolean remove(Object o) {
233+ return map.remove(o)==PRESENT;
234+ }
235+
236+ /**
237+ * Removes all of the elements from this set.
238+ * The set will be empty after this call returns.
239+ */
240+ public void clear() {
241+ map.clear();
242+ }
243+
244+ /**
245+ * Returns a shallow copy of this <tt>HashSet</tt> instance: the elements
246+ * themselves are not cloned.
247+ *
248+ * @return a shallow copy of this set
249+ */
250+ public Object clone() {
251+ try {
252+ HashSet<E> newSet = (HashSet<E>) super.clone();
253+ newSet.map = (HashMap<E, Object>) map.clone();
254+ return newSet;
255+ } catch (CloneNotSupportedException e) {
256+ throw new InternalError();
257+ }
258+ }
259+
260+ /**
261+ * Save the state of this <tt>HashSet</tt> instance to a stream (that is,
262+ * serialize it).
263+ *
264+ * @serialData The capacity of the backing <tt>HashMap</tt> instance
265+ * (int), and its load factor (float) are emitted, followed by
266+ * the size of the set (the number of elements it contains)
267+ * (int), followed by all of its elements (each an Object) in
268+ * no particular order.
269+ */
270+ private void writeObject(java.io.ObjectOutputStream s)
271+ throws java.io.IOException {
272+ // Write out any hidden serialization magic
273+ s.defaultWriteObject();
274+
275+ // Write out HashMap capacity and load factor
276+ s.writeInt(map.capacity());
277+ s.writeFloat(map.loadFactor());
278+
279+ // Write out size
280+ s.writeInt(map.size());
281+
282+ // Write out all elements in the proper order.
283+ for (E e : map.keySet())
284+ s.writeObject(e);
285+ }
286+
287+ /**
288+ * Reconstitute the <tt>HashSet</tt> instance from a stream (that is,
289+ * deserialize it).
290+ */
291+ private void readObject(java.io.ObjectInputStream s)
292+ throws java.io.IOException, ClassNotFoundException {
293+ // Read in any hidden serialization magic
294+ s.defaultReadObject();
295+
296+ // Read in HashMap capacity and load factor and create backing HashMap
297+ int capacity = s.readInt();
298+ float loadFactor = s.readFloat();
299+ map = (((HashSet)this) instanceof LinkedHashSet ?
300+ new LinkedHashMap<E,Object>(capacity, loadFactor) :
301+ new HashMap<E,Object>(capacity, loadFactor));
302+
303+ // Read in size
304+ int size = s.readInt();
305+
306+ // Read in all elements in the proper order.
307+ for (int i=0; i<size; i++) {
308+ E e = (E) s.readObject();
309+ map.put(e, PRESENT);
310+ }
311+ }
312+}