/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.util;


import java.io.Serializable;

/**
 * LinkedHashSet is a variant on HashSet. Its entries are kept in a doubly-linked list.
 * The iteration order is the order in which entries were inserted.
 * <p>
 * Null elements are allowed, and all the optional Set operations are supported.
 * <p>
 * Like HashSet, LinkedHashSet is not thread safe, so access by multiple threads must be synchronized
 * by an external mechanism such as Collections.synchronizedSet.
 * @since 1.4
 */
public class LinkedHashSet<E> extends HashSet<E> implements Set<E>, Cloneable,
		Serializable {
	
	private static final long serialVersionUID = -2851667679971038690L;

	/**
	 * Constructs a new empty instance of LinkedHashSet.
	 */
	public LinkedHashSet() {
		super(new LinkedHashMap<E, HashSet<E>>());
	}

	/**
	 * Constructs a new instance of LinkedHashSet with the specified capacity.
	 * 
	 * @param capacity
	 *            the initial capacity of this HashSet
	 */
	public LinkedHashSet(int capacity) {
		super(new LinkedHashMap<E, HashSet<E>>(capacity));
	}

	/**
	 * Constructs a new instance of LinkedHashSet with the specified capacity
	 * and load factor.
	 * 
	 * @param capacity
	 *            the initial capacity
	 * @param loadFactor
	 *            the initial load factor
	 */
	public LinkedHashSet(int capacity, float loadFactor) {
		super(new LinkedHashMap<E, HashSet<E>>(capacity, loadFactor));
	}

	/**
	 * Constructs a new instance of LinkedHashSet containing the unique elements
	 * in the specified collection.
	 * 
	 * @param collection
	 *            the collection of elements to add
	 */
	public LinkedHashSet(Collection<? extends E> collection) {
		super(new LinkedHashMap<E, HashSet<E>>(collection.size() < 6 ? 11
				: collection.size() * 2));
        for (E e : collection) {
            add(e);
        }
	}

	/* overrides method in HashMap */
	@Override
    HashMap<E, HashSet<E>> createBackingMap(int capacity, float loadFactor) {
		return new LinkedHashMap<E, HashSet<E>>(capacity, loadFactor);
	}
}
