+++ /dev/null
-/* HashSet.java -- a class providing a HashMap-backed Set
- Copyright (C) 1998, 1999, 2001 Free Software Foundation, Inc.
-
-This file is part of GNU Classpath.
-
-GNU Classpath is free software; you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
-any later version.
-
-GNU Classpath 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 for more details.
-
-You should have received a copy of the GNU General Public License
-along with GNU Classpath; see the file COPYING. If not, write to the
-Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
-02111-1307 USA.
-
-Linking this library statically or dynamically with other modules is
-making a combined work based on this library. Thus, the terms and
-conditions of the GNU General Public License cover the whole
-combination.
-
-As a special exception, the copyright holders of this library give you
-permission to link this library with independent modules to produce an
-executable, regardless of the license terms of these independent
-modules, and to copy and distribute the resulting executable under
-terms of your choice, provided that you also meet, for each linked
-independent module, the terms and conditions of the license of that
-module. An independent module is a module which is not derived from
-or based on this library. If you modify this library, you may extend
-this exception to your version of the library, but you are not
-obligated to do so. If you do not wish to do so, delete this
-exception statement from your version. */
-
-
-package java.util;
-
-import java.io.IOException;
-import java.io.Serializable;
-import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
-
-/**
- * This class provides a HashMap-backed implementation of the Set interface.
- * <p>
- *
- * Most operations are O(1), assuming no hash collisions. In the worst
- * case (where all hashes collide), operations are O(n). Setting the
- * initial capacity too low will force many resizing operations, but
- * setting the initial capacity too high (or loadfactor too low) leads
- * to wasted memory and slower iteration.
- * <p>
- *
- * HashSet accepts the null key and null values. It is not synchronized,
- * so if you need multi-threaded access, consider using:<br>
- * <code>Set s = Collections.synchronizedSet(new HashSet(...));</code>
- * <p>
- *
- * The iterators are <i>fail-fast</i>, meaning that any structural
- * modification, except for <code>remove()</code> called on the iterator
- * itself, cause the iterator to throw a
- * {@link ConcurrentModificationException} rather than exhibit
- * non-deterministic behavior.
- *
- * @author Jon Zeppieri
- * @author Eric Blake <ebb9@email.byu.edu>
- * @see Collection
- * @see Set
- * @see TreeSet
- * @see Collections#synchronizedSet(Set)
- * @see HashMap
- * @see LinkedHashSet
- * @since 1.2
- * @status updated to 1.4
- */
-public class HashSet extends AbstractSet
- implements Set, Cloneable, Serializable
-{
- /**
- * Compatible with JDK 1.2.
- */
- private static final long serialVersionUID = -5024744406713321676L;
-
- /**
- * The HashMap which backs this Set.
- */
- private transient HashMap map;
-
- /**
- * Construct a new, empty HashSet whose backing HashMap has the default
- * capacity (11) and loadFacor (0.75).
- */
- public HashSet()
- {
- this(HashMap.DEFAULT_CAPACITY, HashMap.DEFAULT_LOAD_FACTOR);
- }
-
- /**
- * Construct a new, empty HashSet whose backing HashMap has the supplied
- * capacity and the default load factor (0.75).
- *
- * @param initialCapacity the initial capacity of the backing HashMap
- * @throws IllegalArgumentException if the capacity is negative
- */
- public HashSet(int initialCapacity)
- {
- this(initialCapacity, HashMap.DEFAULT_LOAD_FACTOR);
- }
-
- /**
- * Construct a new, empty HashSet whose backing HashMap has the supplied
- * capacity and load factor.
- *
- * @param initialCapacity the initial capacity of the backing HashMap
- * @param loadFactor the load factor of the backing HashMap
- * @throws IllegalArgumentException if either argument is negative, or
- * if loadFactor is POSITIVE_INFINITY or NaN
- */
- public HashSet(int initialCapacity, float loadFactor)
- {
- map = init(initialCapacity, loadFactor);
- }
-
- /**
- * Construct a new HashSet with the same elements as are in the supplied
- * collection (eliminating any duplicates, of course). The backing storage
- * has twice the size of the collection, or the default size of 11,
- * whichever is greater; and the default load factor (0.75).
- *
- * @param c a collection of initial set elements
- * @throws NullPointerException if c is null
- */
- public HashSet(Collection c)
- {
- this(Math.max(2 * c.size(), HashMap.DEFAULT_CAPACITY));
- addAll(c);
- }
-
- /**
- * Adds the given Object to the set if it is not already in the Set.
- * This set permits a null element.
- *
- * @param o the Object to add to this Set
- * @return true if the set did not already contain o
- */
- public boolean add(Object o)
- {
- return map.put(o, "") == null;
- }
-
- /**
- * Empties this Set of all elements; this takes constant time.
- */
- public void clear()
- {
- map.clear();
- }
-
- /**
- * Returns a shallow copy of this Set. The Set itself is cloned; its
- * elements are not.
- *
- * @return a shallow clone of the set
- */
- public Object clone()
- {
- HashSet copy = null;
- try
- {
- copy = (HashSet) super.clone();
- }
- catch (CloneNotSupportedException x)
- {
- // Impossible to get here.
- }
- copy.map = (HashMap) map.clone();
- return copy;
- }
-
- /**
- * Returns true if the supplied element is in this Set.
- *
- * @param o the Object to look for
- * @return true if it is in the set
- */
- public boolean contains(Object o)
- {
- return map.containsKey(o);
- }
-
- /**
- * Returns true if this set has no elements in it.
- *
- * @return <code>size() == 0</code>.
- */
- public boolean isEmpty()
- {
- return map.size == 0;
- }
-
- /**
- * Returns an Iterator over the elements of this Set, which visits the
- * elements in no particular order. For this class, the Iterator allows
- * removal of elements. The iterator is fail-fast, and will throw a
- * ConcurrentModificationException if the set is modified externally.
- *
- * @return a set iterator
- * @see ConcurrentModificationException
- */
- public Iterator iterator()
- {
- // Avoid creating intermediate keySet() object by using non-public API.
- return map.iterator(HashMap.KEYS);
- }
-
- /**
- * Removes the supplied Object from this Set if it is in the Set.
- *
- * @param o the object to remove
- * @return true if an element was removed
- */
- public boolean remove(Object o)
- {
- return (map.remove(o) != null);
- }
-
- /**
- * Returns the number of elements in this Set (its cardinality).
- *
- * @return the size of the set
- */
- public int size()
- {
- return map.size;
- }
-
- /**
- * Helper method which initializes the backing Map. Overridden by
- * LinkedHashSet for correct semantics.
- *
- * @param capacity the initial capacity
- * @param load the initial load factor
- * @return the backing HashMap
- */
- HashMap init(int capacity, float load)
- {
- return new HashMap(capacity, load);
- }
-
- /**
- * Serializes this object to the given stream.
- *
- * @param s the stream to write to
- * @throws IOException if the underlying stream fails
- * @serialData the <i>capacity</i> (int) and <i>loadFactor</i> (float)
- * of the backing store, followed by the set size (int),
- * then a listing of its elements (Object) in no order
- */
- private void writeObject(ObjectOutputStream s) throws IOException
- {
- s.defaultWriteObject();
- // Avoid creating intermediate keySet() object by using non-public API.
- Iterator it = map.iterator(HashMap.KEYS);
- s.writeInt(map.buckets.length);
- s.writeFloat(map.loadFactor);
- s.writeInt(map.size);
- while (it.hasNext())
- s.writeObject(it.next());
- }
-
- /**
- * Deserializes this object from the given stream.
- *
- * @param s the stream to read from
- * @throws ClassNotFoundException if the underlying stream fails
- * @throws IOException if the underlying stream fails
- * @serialData the <i>capacity</i> (int) and <i>loadFactor</i> (float)
- * of the backing store, followed by the set size (int),
- * then a listing of its elements (Object) in no order
- */
- private void readObject(ObjectInputStream s)
- throws IOException, ClassNotFoundException
- {
- s.defaultReadObject();
-
- map = init(s.readInt(), s.readFloat());
- for (int size = s.readInt(); size > 0; size--)
- map.put(s.readObject(), "");
- }
-}
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