| /* |
| * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
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| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
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| * questions. |
| */ |
| |
| 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>The {@link #addFirst addFirst} and {@link #addLast addLast} methods of this class |
| * throw {@code UnsupportedOperationException}. The encounter order of elements is determined |
| * by the comparison method; therefore, explicit positioning is not supported. |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework"> |
| * 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<>()); |
| } |
| |
| /** |
| * 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 |
| * {@code Objects.equals(o, e)}. |
| * |
| * @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 |
| * {@code Objects.equals(e, e2)}. |
| * 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 |
| * {@code Objects.equals(o, e)}, |
| * 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<E, Object> map) { |
| SortedSet<? extends E> set = (SortedSet<? extends E>) c; |
| if (Objects.equals(set.comparator(), map.comparator())) { |
| 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(); |
| } |
| |
| /** |
| * Throws {@code UnsupportedOperationException}. The encounter order induced by this |
| * set's comparison method determines the position of elements, so explicit positioning |
| * is not supported. |
| * |
| * @throws UnsupportedOperationException always |
| * @since 21 |
| */ |
| public void addFirst(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Throws {@code UnsupportedOperationException}. The encounter order induced by this |
| * set's comparison method determines the position of elements, so explicit positioning |
| * is not supported. |
| * |
| * @throws UnsupportedOperationException always |
| * @since 21 |
| */ |
| public void addLast(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * 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). |
| */ |
| @java.io.Serial |
| 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). |
| */ |
| @java.io.Serial |
| 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); |
| } |
| |
| @java.io.Serial |
| private static final long serialVersionUID = -2479143000061671589L; |
| } |
