/*
* Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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package java.util;
/**
* A {@link NavigableSet} implementation based on a {@link TreeMap}.
* The elements are ordered using their {@linkplain Comparable natural
* ordering}, or by a {@link Comparator} provided at set creation
* time, depending on which constructor is used.
*
* <p>This implementation provides guaranteed log(n) time cost for the basic
* operations ({@code add}, {@code remove} and {@code contains}).
*
* <p>Note that the ordering maintained by a set (whether or not an explicit
* comparator is provided) must be <i>consistent with equals</i> if it is to
* correctly implement the {@code Set} interface. (See {@code Comparable}
* or {@code Comparator} for a precise definition of <i>consistent with
* equals</i>.) This is so because the {@code Set} interface is defined in
* terms of the {@code equals} operation, but a {@code TreeSet} instance
* performs all element comparisons using its {@code compareTo} (or
* {@code compare}) method, so two elements that are deemed equal by this method
* are, from the standpoint of the set, equal. The behavior of a set
* <i>is</i> well-defined even if its ordering is inconsistent with equals; it
* just fails to obey the general contract of the {@code Set} interface.
*
* <p><strong>Note that this implementation is not synchronized.</strong>
* If multiple threads access a tree set concurrently, and at least one
* of the threads modifies the set, it <i>must</i> 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#synchronizedSortedSet Collections.synchronizedSortedSet}
* method. This is best done at creation time, to prevent accidental
* unsynchronized access to the set: <pre>
* SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));</pre>
*
* <p>The iterators returned by this class's {@code iterator} method are
* <i>fail-fast</i>: if the set is modified at any time after the iterator is
* created, in any way except through the iterator's own {@code remove}
* 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 {@code ConcurrentModificationException} 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 Collection
* @see Set
* @see HashSet
* @see Comparable
* @see Comparator
* @see TreeMap
* @since 1.2
*/
public class
TreeSet<E> extends
AbstractSet<E>
implements
NavigableSet<E>,
Cloneable, java.io.
Serializable
{
/**
* The backing map.
*/
private transient
NavigableMap<E,
Object>
m;
// Dummy value to associate with an Object in the backing Map
private static final
Object PRESENT = new
Object();
/**
* Constructs a set backed by the specified navigable map.
*/
TreeSet(
NavigableMap<E,
Object>
m) {
this.
m =
m;
}
/**
* Constructs a new, empty tree set, sorted according to the
* natural ordering of its elements. All elements inserted into
* the set must implement the {@link Comparable} interface.
* Furthermore, all such elements must be <i>mutually
* comparable</i>: {@code e1.compareTo(e2)} must not throw a
* {@code ClassCastException} for any elements {@code e1} and
* {@code e2} in the set. If the user attempts to add an element
* to the set that violates this constraint (for example, the user
* attempts to add a string element to a set whose elements are
* integers), the {@code add} call will throw a
* {@code ClassCastException}.
*/
public
TreeSet() {
this(new
TreeMap<E,
Object>());
}
/**
* Constructs a new, empty tree set, sorted according to the specified
* comparator. All elements inserted into the set must be <i>mutually
* comparable</i> by the specified comparator: {@code comparator.compare(e1,
* e2)} must not throw a {@code ClassCastException} for any elements
* {@code e1} and {@code e2} in the set. If the user attempts to add
* an element to the set that violates this constraint, the
* {@code add} call will throw a {@code ClassCastException}.
*
* @param comparator the comparator that will be used to order this set.
* If {@code null}, the {@linkplain Comparable natural
* ordering} of the elements will be used.
*/
public
TreeSet(
Comparator<? super E>
comparator) {
this(new
TreeMap<>(
comparator));
}
/**
* Constructs a new tree set containing the elements in the specified
* collection, sorted according to the <i>natural ordering</i> of its
* elements. All elements inserted into the set must implement the
* {@link Comparable} interface. Furthermore, all such elements must be
* <i>mutually comparable</i>: {@code e1.compareTo(e2)} must not throw a
* {@code ClassCastException} for any elements {@code e1} and
* {@code e2} in the set.
*
* @param c collection whose elements will comprise the new set
* @throws ClassCastException if the elements in {@code c} are
* not {@link Comparable}, or are not mutually comparable
* @throws NullPointerException if the specified collection is null
*/
public
TreeSet(
Collection<? extends E>
c) {
this();
addAll(
c);
}
/**
* Constructs a new tree set containing the same elements and
* using the same ordering as the specified sorted set.
*
* @param s sorted set whose elements will comprise the new set
* @throws NullPointerException if the specified sorted set is null
*/
public
TreeSet(
SortedSet<E>
s) {
this(
s.
comparator());
addAll(
s);
}
/**
* Returns an iterator over the elements in this set in ascending order.
*
* @return an iterator over the elements in this set in ascending order
*/
public
Iterator<E>
iterator() {
return
m.
navigableKeySet().
iterator();
}
/**
* Returns an iterator over the elements in this set in descending order.
*
* @return an iterator over the elements in this set in descending order
* @since 1.6
*/
public
Iterator<E>
descendingIterator() {
return
m.
descendingKeySet().
iterator();
}
/**
* @since 1.6
*/
public
NavigableSet<E>
descendingSet() {
return new
TreeSet<>(
m.
descendingMap());
}
/**
* Returns the number of elements in this set (its cardinality).
*
* @return the number of elements in this set (its cardinality)
*/
public int
size() {
return
m.
size();
}
/**
* Returns {@code true} if this set contains no elements.
*
* @return {@code true} if this set contains no elements
*/
public boolean
isEmpty() {
return
m.
isEmpty();
}
/**
* Returns {@code true} if this set contains the specified element.
* More formally, returns {@code true} if and only if this set
* contains an element {@code e} such that
* <tt>(o==null ? e==null : o.equals(e))</tt>.
*
* @param o object to be checked for containment in this set
* @return {@code true} if this set contains the specified element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in the set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
public boolean
contains(
Object o) {
return
m.
containsKey(
o);
}
/**
* Adds the specified element to this set if it is not already present.
* More formally, adds the specified element {@code e} to this set if
* the set contains no element {@code e2} such that
* <tt>(e==null ? e2==null : e.equals(e2))</tt>.
* If this set already contains the element, the call leaves the set
* unchanged and returns {@code false}.
*
* @param e element to be added to this set
* @return {@code true} if this set did not already contain the specified
* element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in this set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
public boolean
add(E
e) {
return
m.
put(
e,
PRESENT)==null;
}
/**
* Removes the specified element from this set if it is present.
* More formally, removes an element {@code e} such that
* <tt>(o==null ? e==null : o.equals(e))</tt>,
* if this set contains such an element. Returns {@code true} if
* this set contained the element (or equivalently, if this set
* changed as a result of the call). (This set will not contain the
* element once the call returns.)
*
* @param o object to be removed from this set, if present
* @return {@code true} if this set contained the specified element
* @throws ClassCastException if the specified object cannot be compared
* with the elements currently in this set
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
*/
public boolean
remove(
Object o) {
return
m.
remove(
o)==
PRESENT;
}
/**
* Removes all of the elements from this set.
* The set will be empty after this call returns.
*/
public void
clear() {
m.
clear();
}
/**
* Adds all of the elements in the specified collection to this set.
*
* @param c collection containing elements to be added to this set
* @return {@code true} if this set changed as a result of the call
* @throws ClassCastException if the elements provided cannot be compared
* with the elements currently in the set
* @throws NullPointerException if the specified collection is null or
* if any element is null and this set uses natural ordering, or
* its comparator does not permit null elements
*/
public boolean
addAll(
Collection<? extends E>
c) {
// Use linear-time version if applicable
if (
m.
size()==0 &&
c.
size() > 0 &&
c instanceof
SortedSet &&
m instanceof
TreeMap) {
SortedSet<? extends E>
set = (
SortedSet<? extends E>)
c;
TreeMap<E,
Object>
map = (
TreeMap<E,
Object>)
m;
Comparator<?>
cc =
set.
comparator();
Comparator<? super E>
mc =
map.
comparator();
if (
cc==
mc || (
cc != null &&
cc.
equals(
mc))) {
map.
addAllForTreeSet(
set,
PRESENT);
return true;
}
}
return super.addAll(
c);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} or {@code toElement}
* is null and this set uses natural ordering, or its comparator
* does not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
public
NavigableSet<E>
subSet(E
fromElement, boolean
fromInclusive,
E
toElement, boolean
toInclusive) {
return new
TreeSet<>(
m.
subMap(
fromElement,
fromInclusive,
toElement,
toInclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toElement} is null and
* this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
public
NavigableSet<E>
headSet(E
toElement, boolean
inclusive) {
return new
TreeSet<>(
m.
headMap(
toElement,
inclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} is null and
* this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
* @since 1.6
*/
public
NavigableSet<E>
tailSet(E
fromElement, boolean
inclusive) {
return new
TreeSet<>(
m.
tailMap(
fromElement,
inclusive));
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} or
* {@code toElement} is null and this set uses natural ordering,
* or its comparator does not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public
SortedSet<E>
subSet(E
fromElement, E
toElement) {
return
subSet(
fromElement, true,
toElement, false);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code toElement} is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public
SortedSet<E>
headSet(E
toElement) {
return
headSet(
toElement, false);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if {@code fromElement} is null
* and this set uses natural ordering, or its comparator does
* not permit null elements
* @throws IllegalArgumentException {@inheritDoc}
*/
public
SortedSet<E>
tailSet(E
fromElement) {
return
tailSet(
fromElement, true);
}
public
Comparator<? super E>
comparator() {
return
m.
comparator();
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
public E
first() {
return
m.
firstKey();
}
/**
* @throws NoSuchElementException {@inheritDoc}
*/
public E
last() {
return
m.
lastKey();
}
// NavigableSet API methods
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
public E
lower(E
e) {
return
m.
lowerKey(
e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
public E
floor(E
e) {
return
m.
floorKey(
e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
public E
ceiling(E
e) {
return
m.
ceilingKey(
e);
}
/**
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException if the specified element is null
* and this set uses natural ordering, or its comparator
* does not permit null elements
* @since 1.6
*/
public E
higher(E
e) {
return
m.
higherKey(
e);
}
/**
* @since 1.6
*/
public E
pollFirst() {
Map.
Entry<E,?>
e =
m.
pollFirstEntry();
return (
e == null) ? null :
e.
getKey();
}
/**
* @since 1.6
*/
public E
pollLast() {
Map.
Entry<E,?>
e =
m.
pollLastEntry();
return (
e == null) ? null :
e.
getKey();
}
/**
* Returns a shallow copy of this {@code TreeSet} instance. (The elements
* themselves are not cloned.)
*
* @return a shallow copy of this set
*/
@
SuppressWarnings("unchecked")
public
Object clone() {
TreeSet<E>
clone;
try {
clone = (
TreeSet<E>) super.clone();
} catch (
CloneNotSupportedException e) {
throw new
InternalError(
e);
}
clone.
m = new
TreeMap<>(
m);
return
clone;
}
/**
* Save the state of the {@code TreeSet} instance to a stream (that is,
* serialize it).
*
* @serialData Emits the comparator used to order this set, or
* {@code null} if it obeys its elements' natural ordering
* (Object), followed by the size of the set (the number of
* elements it contains) (int), followed by all of its
* elements (each an Object) in order (as determined by the
* set's Comparator, or by the elements' natural ordering if
* the set has no Comparator).
*/
private void
writeObject(java.io.
ObjectOutputStream s)
throws java.io.
IOException {
// Write out any hidden stuff
s.
defaultWriteObject();
// Write out Comparator
s.
writeObject(
m.
comparator());
// Write out size
s.
writeInt(
m.
size());
// Write out all elements in the proper order.
for (E
e :
m.
keySet())
s.
writeObject(
e);
}
/**
* Reconstitute the {@code TreeSet} instance from a stream (that is,
* deserialize it).
*/
private void
readObject(java.io.
ObjectInputStream s)
throws java.io.
IOException,
ClassNotFoundException {
// Read in any hidden stuff
s.
defaultReadObject();
// Read in Comparator
@
SuppressWarnings("unchecked")
Comparator<? super E>
c = (
Comparator<? super E>)
s.
readObject();
// Create backing TreeMap
TreeMap<E,
Object>
tm = new
TreeMap<>(
c);
m =
tm;
// Read in size
int
size =
s.
readInt();
tm.
readTreeSet(
size,
s,
PRESENT);
}
/**
* Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
* and <em>fail-fast</em> {@link Spliterator} over the elements in this
* set.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
* {@link Spliterator#DISTINCT}, {@link Spliterator#SORTED}, and
* {@link Spliterator#ORDERED}. Overriding implementations should document
* the reporting of additional characteristic values.
*
* <p>The spliterator's comparator (see
* {@link java.util.Spliterator#getComparator()}) is {@code null} if
* the tree set's comparator (see {@link #comparator()}) is {@code null}.
* Otherwise, the spliterator's comparator is the same as or imposes the
* same total ordering as the tree set's comparator.
*
* @return a {@code Spliterator} over the elements in this set
* @since 1.8
*/
public
Spliterator<E>
spliterator() {
return
TreeMap.
keySpliteratorFor(
m);
}
private static final long
serialVersionUID = -2479143000061671589L;
}