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