content: /*
   * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
   * 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.
   */
  
  package java.util;
  
  /**
   * <p>Hash table and linked list implementation of the <tt>Set</tt> interface,
   * with predictable iteration order.  This implementation differs from
   * <tt>HashSet</tt> in that it maintains a doubly-linked list running through
   * all of its entries.  This linked list defines the iteration ordering,
   * which is the order in which elements were inserted into the set
   * (<i>insertion-order</i>).  Note that insertion order is <i>not</i> affected
   * if an element is <i>re-inserted</i> into the set.  (An element <tt>e</tt>
   * is reinserted into a set <tt>s</tt> if <tt>s.add(e)</tt> is invoked when
   * <tt>s.contains(e)</tt> would return <tt>true</tt> immediately prior to
   * the invocation.)
   *
   * <p>This implementation spares its clients from the unspecified, generally
   * chaotic ordering provided by {@link HashSet}, without incurring the
   * increased cost associated with {@link TreeSet}.  It can be used to
   * produce a copy of a set that has the same order as the original, regardless
   * of the original set's implementation:
   * <pre>
   *     void foo(Set s) {
   *         Set copy = new LinkedHashSet(s);
   *         ...
   *     }
   * </pre>
   * This technique is particularly useful if a module takes a set on input,
   * copies it, and later returns results whose order is determined by that of
   * the copy.  (Clients generally appreciate having things returned in the same
   * order they were presented.)
   *
   * <p>This class provides all of the optional <tt>Set</tt> operations, and
   * permits null elements.  Like <tt>HashSet</tt>, it provides constant-time
   * performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and
   * <tt>remove</tt>), assuming the hash function disperses elements
   * properly among the buckets.  Performance is likely to be just slightly
   * below that of <tt>HashSet</tt>, due to the added expense of maintaining the
   * linked list, with one exception: Iteration over a <tt>LinkedHashSet</tt>
   * requires time proportional to the <i>size</i> of the set, regardless of
   * its capacity.  Iteration over a <tt>HashSet</tt> is likely to be more
   * expensive, requiring time proportional to its <i>capacity</i>.
   *
   * <p>A linked hash set has two parameters that affect its performance:
   * <i>initial capacity</i> and <i>load factor</i>.  They are defined precisely
   * as for <tt>HashSet</tt>.  Note, however, that the penalty for choosing an
   * excessively high value for initial capacity is less severe for this class
   * than for <tt>HashSet</tt>, as iteration times for this class are unaffected
   * by capacity.
   *
   * <p><strong>Note that this implementation is not synchronized.</strong>
   * If multiple threads access a linked hash set concurrently, and at least
   * one of the threads modifies the set, it <em>must</em> be synchronized
   * externally.  This is typically accomplished by synchronizing on some
   * object that naturally encapsulates the set.
   *
   * If no such object exists, the set should be "wrapped" using the
   * {@link Collections#synchronizedSet Collections.synchronizedSet}
   * method.  This is best done at creation time, to prevent accidental
   * unsynchronized access to the set: <pre>
   *   Set s = Collections.synchronizedSet(new LinkedHashSet(...));</pre>
   *
   * <p>The iterators returned by this class's <tt>iterator</tt> method are
   * <em>fail-fast</em>: if the set is modified at any time after the iterator
   * is created, in any way except through the iterator's own <tt>remove</tt>
   * method, the iterator will throw a {@link ConcurrentModificationException}.
   * Thus, in the face of concurrent modification, the iterator fails quickly
   * and cleanly, rather than risking arbitrary, non-deterministic behavior at
   * an undetermined time in the future.
   *
   * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
   * as it is, generally speaking, impossible to make any hard guarantees in the
   * presence of unsynchronized concurrent modification.  Fail-fast iterators
   * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
   * Therefore, it would be wrong to write a program that depended on this
   * exception for its correctness:   <i>the fail-fast behavior of iterators
   * should be used only to detect bugs.</i>
   *
   * <p>This class is a member of the
   * <a href="{@docRoot}/../technotes/guides/collections/index.html">
   * Java Collections Framework</a>.
   *
   * @param <E> the type of elements maintained by this set
   *
   * @author  Josh Bloch
   * @see     Object#hashCode()
   * @see     Collection
   * @see     Set
   * @see     HashSet
   * @see     TreeSet
   * @see     Hashtable
   * @since   1.4
   */
  
  public class LinkedHashSet<E>
      extends HashSet<E>
      implements Set<E>, Cloneable, java.io.Serializable {
  
      private static final long serialVersionUID = -2851667679971038690L;
  
      /**
       * Constructs a new, empty linked hash set with the specified initial
       * capacity and load factor.
       *
       * @param      initialCapacity the initial capacity of the linked hash set
       * @param      loadFactor      the load factor of the linked hash set
       * @throws     IllegalArgumentException  if the initial capacity is less
       *               than zero, or if the load factor is nonpositive
       */
      public LinkedHashSet(int initialCapacity, float loadFactor) {
          super(initialCapacity, loadFactor, true);
      }
  
      /**
       * Constructs a new, empty linked hash set with the specified initial
       * capacity and the default load factor (0.75).
       *
       * @param   initialCapacity   the initial capacity of the LinkedHashSet
       * @throws  IllegalArgumentException if the initial capacity is less
       *              than zero
       */
      public LinkedHashSet(int initialCapacity) {
          super(initialCapacity, .75f, true);
      }
  
      /**
       * Constructs a new, empty linked hash set with the default initial
       * capacity (16) and load factor (0.75).
       */
      public LinkedHashSet() {
          super(16, .75f, true);
      }
  
      /**
       * Constructs a new linked hash set with the same elements as the
       * specified collection.  The linked hash set is created with an initial
       * capacity sufficient to hold the elements in the specified collection
       * and the default load factor (0.75).
       *
       * @param c  the collection whose elements are to be placed into
       *           this set
       * @throws NullPointerException if the specified collection is null
       */
      public LinkedHashSet(Collection<? extends E> c) {
          super(Math.max(2*c.size(), 11), .75f, true);
          addAll(c);
      }
  
      /**
       * Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
       * and <em>fail-fast</em> {@code Spliterator} over the elements in this set.
       *
       * <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
       * {@link Spliterator#DISTINCT}, and {@code ORDERED}.  Implementations
       * should document the reporting of additional characteristic values.
       *
       * @implNote
       * The implementation creates a
       * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
       * from the set's {@code Iterator}.  The spliterator inherits the
       * <em>fail-fast</em> properties of the set's iterator.
       * The created {@code Spliterator} additionally reports
       * {@link Spliterator#SUBSIZED}.
       *
       * @return a {@code Spliterator} over the elements in this set
       * @since 1.8
       */
      @Override
      public Spliterator<E> spliterator() {
          return Spliterators.spliterator(this, Spliterator.DISTINCT | Spliterator.ORDERED);
      }
  }
  