/*
* 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.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
/**
* TreeSet is an implementation of SortedSet. All optional operations (adding
* and removing) are supported. The elements can be any objects which are
* comparable to each other either using their natural order or a specified
* Comparator.
*
* @since 1.2
*/
public class TreeSet<E> extends AbstractSet<E> implements NavigableSet<E>,
Cloneable, Serializable {
private static final long serialVersionUID = -2479143000061671589L;
/** Keys are this set's elements. Values are always Boolean.TRUE */
private transient NavigableMap<E, Object> backingMap;
private transient NavigableSet<E> descendingSet;
TreeSet(NavigableMap<E, Object> map) {
backingMap = map;
}
/**
* Constructs a new empty instance of {@code TreeSet} which uses natural
* ordering.
*/
public TreeSet() {
backingMap = new TreeMap<E, Object>();
}
/**
* Constructs a new instance of {@code TreeSet} which uses natural ordering
* and containing the unique elements in the specified collection.
*
* @param collection
* the collection of elements to add.
* @throws ClassCastException
* when an element in the collection does not implement the
* Comparable interface, or the elements in the collection
* cannot be compared.
*/
public TreeSet(Collection<? extends E> collection) {
this();
addAll(collection);
}
/**
* Constructs a new empty instance of {@code TreeSet} which uses the
* specified comparator.
*
* @param comparator
* the comparator to use.
*/
public TreeSet(Comparator<? super E> comparator) {
backingMap = new TreeMap<E, Object>(comparator);
}
/**
* Constructs a new instance of {@code TreeSet} containing the elements of
* the specified SortedSet and using the same Comparator.
*
* @param set
* the SortedSet of elements to add.
*/
public TreeSet(SortedSet<E> set) {
this(set.comparator());
Iterator<E> it = set.iterator();
while (it.hasNext()) {
add(it.next());
}
}
/**
* Adds the specified object to this {@code TreeSet}.
*
* @param object
* the object to add.
* @return {@code true} when this {@code TreeSet} did not already contain
* the object, {@code false} otherwise.
* @throws ClassCastException
* when the object cannot be compared with the elements in this
* {@code TreeSet}.
* @throws NullPointerException
* when the object is null and the comparator cannot handle
* null.
*/
@Override
public boolean add(E object) {
return backingMap.put(object, Boolean.TRUE) == null;
}
/**
* Adds the objects in the specified collection to this {@code TreeSet}.
*
* @param collection
* the collection of objects to add.
* @return {@code true} if this {@code TreeSet} was modified, {@code false}
* otherwise.
* @throws ClassCastException
* when an object in the collection cannot be compared with the
* elements in this {@code TreeSet}.
* @throws NullPointerException
* when an object in the collection is null and the comparator
* cannot handle null.
*/
@Override
public boolean addAll(Collection<? extends E> collection) {
return super.addAll(collection);
}
/**
* Removes all elements from this {@code TreeSet}, leaving it empty.
*
* @see #isEmpty
* @see #size
*/
@Override
public void clear() {
backingMap.clear();
}
/**
* Returns a new {@code TreeSet} with the same elements, size and comparator
* as this {@code TreeSet}.
*
* @return a shallow copy of this {@code TreeSet}.
* @see java.lang.Cloneable
*/
@SuppressWarnings("unchecked")
@Override
public Object clone() {
try {
TreeSet<E> clone = (TreeSet<E>) super.clone();
if (backingMap instanceof TreeMap) {
clone.backingMap = (NavigableMap<E, Object>) ((TreeMap<E, Object>) backingMap)
.clone();
} else {
clone.backingMap = new TreeMap<E, Object>(backingMap);
}
return clone;
} catch (CloneNotSupportedException e) {
throw new AssertionError(e);
}
}
/**
* Returns the comparator used to compare elements in this {@code TreeSet}.
*
* @return a Comparator or null if the natural ordering is used
*/
public Comparator<? super E> comparator() {
return backingMap.comparator();
}
/**
* Searches this {@code TreeSet} for the specified object.
*
* @param object
* the object to search for.
* @return {@code true} if {@code object} is an element of this
* {@code TreeSet}, {@code false} otherwise.
* @throws ClassCastException
* when the object cannot be compared with the elements in this
* {@code TreeSet}.
* @throws NullPointerException
* when the object is null and the comparator cannot handle
* null.
*/
@Override
public boolean contains(Object object) {
return backingMap.containsKey(object);
}
/**
* Returns true if this {@code TreeSet} has no element, otherwise false.
*
* @return true if this {@code TreeSet} has no element.
* @see #size
*/
@Override
public boolean isEmpty() {
return backingMap.isEmpty();
}
/**
* Returns an Iterator on the elements of this {@code TreeSet}.
*
* @return an Iterator on the elements of this {@code TreeSet}.
* @see Iterator
*/
@Override
public Iterator<E> iterator() {
return backingMap.keySet().iterator();
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#descendingIterator()
* @since 1.6
*/
public Iterator<E> descendingIterator() {
return descendingSet().iterator();
}
/**
* Removes an occurrence of the specified object from this {@code TreeSet}.
*
* @param object
* the object to remove.
* @return {@code true} if this {@code TreeSet} was modified, {@code false}
* otherwise.
* @throws ClassCastException
* when the object cannot be compared with the elements in this
* {@code TreeSet}.
* @throws NullPointerException
* when the object is null and the comparator cannot handle
* null.
*/
@Override
public boolean remove(Object object) {
return backingMap.remove(object) != null;
}
/**
* Returns the number of elements in this {@code TreeSet}.
*
* @return the number of elements in this {@code TreeSet}.
*/
@Override
public int size() {
return backingMap.size();
}
/**
* Returns the first element in this set.
* @exception NoSuchElementException when this TreeSet is empty
*/
public E first() {
return backingMap.firstKey();
}
/**
* Returns the last element in this set.
* @exception NoSuchElementException when this TreeSet is empty
*/
public E last() {
return backingMap.lastKey();
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#pollFirst()
* @since 1.6
*/
public E pollFirst() {
Map.Entry<E, Object> entry = backingMap.pollFirstEntry();
return (entry == null) ? null : entry.getKey();
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#pollLast()
* @since 1.6
*/
public E pollLast() {
Map.Entry<E, Object> entry = backingMap.pollLastEntry();
return (entry == null) ? null : entry.getKey();
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#higher(java.lang.Object)
* @since 1.6
*/
public E higher(E e) {
return backingMap.higherKey(e);
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#lower(java.lang.Object)
* @since 1.6
*/
public E lower(E e) {
return backingMap.lowerKey(e);
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#ceiling(java.lang.Object)
* @since 1.6
*/
public E ceiling(E e) {
return backingMap.ceilingKey(e);
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#floor(java.lang.Object)
* @since 1.6
*/
public E floor(E e) {
return backingMap.floorKey(e);
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#descendingSet()
* @since 1.6
*/
public NavigableSet<E> descendingSet() {
return (descendingSet != null) ? descendingSet
: (descendingSet = new TreeSet<E>(backingMap.descendingMap()));
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#subSet(Object, boolean, Object, boolean)
* @since 1.6
*/
@SuppressWarnings("unchecked")
public NavigableSet<E> subSet(E start, boolean startInclusive, E end,
boolean endInclusive) {
Comparator<? super E> c = backingMap.comparator();
int compare = (c == null) ? ((Comparable<E>) start).compareTo(end) : c
.compare(start, end);
if (compare <= 0) {
return new TreeSet<E>(backingMap.subMap(start, startInclusive, end,
endInclusive));
}
throw new IllegalArgumentException();
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#headSet(Object, boolean)
* @since 1.6
*/
@SuppressWarnings("unchecked")
public NavigableSet<E> headSet(E end, boolean endInclusive) {
// Check for errors
Comparator<? super E> c = backingMap.comparator();
if (c == null) {
((Comparable<E>) end).compareTo(end);
} else {
c.compare(end, end);
}
return new TreeSet<E>(backingMap.headMap(end, endInclusive));
}
/**
* {@inheritDoc}
*
* @see java.util.NavigableSet#tailSet(Object, boolean)
* @since 1.6
*/
@SuppressWarnings("unchecked")
public NavigableSet<E> tailSet(E start, boolean startInclusive) {
// Check for errors
Comparator<? super E> c = backingMap.comparator();
if (c == null) {
((Comparable<E>) start).compareTo(start);
} else {
c.compare(start, start);
}
return new TreeSet<E>(backingMap.tailMap(start, startInclusive));
}
/**
* Returns a {@code SortedSet} of the specified portion of this {@code TreeSet} which
* contains elements greater or equal to the start element but less than the
* end element. The returned SortedSet is backed by this TreeSet so changes
* to one are reflected by the other.
*
* @param start
* the start element
* @param end
* the end element
* @return a subset where the elements are greater or equal to
* <code>start</code> and less than <code>end</code>
*
* @exception ClassCastException
* when the start or end object cannot be compared with the
* elements in this TreeSet
* @exception NullPointerException
* when the start or end object is null and the comparator
* cannot handle null
*/
@SuppressWarnings("unchecked")
public SortedSet<E> subSet(E start, E end) {
return subSet(start, true, end, false);
}
/**
* Returns a {@code SortedSet} of the specified portion of this {@code TreeSet} which
* contains elements less than the end element. The returned SortedSet is
* backed by this TreeSet so changes to one are reflected by the other.
*
* @param end
* the end element
* @return a subset where the elements are less than <code>end</code>
*
* @exception ClassCastException
* when the end object cannot be compared with the elements
* in this TreeSet
* @exception NullPointerException
* when the end object is null and the comparator cannot
* handle null
*/
@SuppressWarnings("unchecked")
public SortedSet<E> headSet(E end) {
return headSet(end, false);
}
/**
* Returns a {@code SortedSet} of the specified portion of this {@code TreeSet} which
* contains elements greater or equal to the start element. The returned
* SortedSet is backed by this TreeSet so changes to one are reflected by
* the other.
*
* @param start
* the start element
* @return a subset where the elements are greater or equal to
* <code>start</code>
*
* @exception ClassCastException
* when the start object cannot be compared with the elements
* in this TreeSet
* @exception NullPointerException
* when the start object is null and the comparator cannot
* handle null
*/
@SuppressWarnings("unchecked")
public SortedSet<E> tailSet(E start) {
return tailSet(start, true);
}
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(backingMap.comparator());
int size = backingMap.size();
stream.writeInt(size);
if (size > 0) {
Iterator<E> it = backingMap.keySet().iterator();
while (it.hasNext()) {
stream.writeObject(it.next());
}
}
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream stream) throws IOException,
ClassNotFoundException {
stream.defaultReadObject();
TreeMap<E, Object> map = new TreeMap<E, Object>(
(Comparator<? super E>) stream.readObject());
int size = stream.readInt();
if (size > 0) {
for (int i=0; i<size; i++) {
E elem = (E)stream.readObject();
map.put(elem, Boolean.TRUE);
}
}
backingMap = map;
}
}