| /* |
| * Copyright 2008 Google Inc. |
| * |
| * Licensed 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; |
| |
| /** |
| * Implements a set using a TreeMap. <a |
| * href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/TreeSet.html">[Sun |
| * docs]</a> |
| * |
| * @param <E> element type. |
| */ |
| public class TreeSet<E> extends AbstractSet<E> implements SortedSet<E>, Serializable { |
| |
| /** |
| * TreeSet is stored as a TreeMap of the requested type to a constant Boolean. |
| */ |
| private SortedMap<E, Boolean> map; |
| |
| public TreeSet() { |
| map = new TreeMap<E, Boolean>(); |
| } |
| |
| public TreeSet(Collection<? extends E> c) { |
| this(); |
| addAll(c); |
| } |
| |
| public TreeSet(Comparator<? super E> c) { |
| if (c == null) { |
| map = new TreeMap<E, Boolean>(); |
| } else { |
| map = new TreeMap<E, Boolean>(c); |
| } |
| } |
| |
| public TreeSet(SortedSet<E> s) { |
| this(s.comparator()); |
| // TODO(jat): more efficient implementation |
| addAll(s); |
| } |
| |
| /** |
| * Used to wrap subset maps in a new TreeSet. |
| * |
| * @param map map to use for backing store |
| */ |
| private TreeSet(SortedMap<E, Boolean> map) { |
| this.map = map; |
| } |
| |
| @Override |
| public boolean add(E o) { |
| // Use Boolean.FALSE as a convenient non-null value to store in the map |
| return map.put(o, Boolean.FALSE) == null; |
| } |
| |
| @Override |
| public void clear() { |
| map.clear(); |
| } |
| |
| public Comparator<? super E> comparator() { |
| return map.comparator(); |
| } |
| |
| @Override |
| public boolean contains(Object o) { |
| return map.containsKey(o); |
| } |
| |
| public E first() { |
| return map.firstKey(); |
| } |
| |
| public SortedSet<E> headSet(E toElement) { |
| return new TreeSet<E>(map.headMap(toElement)); |
| } |
| |
| @Override |
| public Iterator<E> iterator() { |
| return map.keySet().iterator(); |
| } |
| |
| public E last() { |
| return map.lastKey(); |
| } |
| |
| @Override |
| public boolean remove(Object o) { |
| return map.remove(o) != null; |
| } |
| |
| @Override |
| public int size() { |
| return map.size(); |
| } |
| |
| public SortedSet<E> subSet(E fromElement, E toElement) { |
| return new TreeSet<E>(map.subMap(fromElement, toElement)); |
| } |
| |
| public SortedSet<E> tailSet(E fromElement) { |
| return new TreeSet<E>(map.tailMap(fromElement)); |
| } |
| } |