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	/*
	* Copyright (c) 2003, 2019, 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
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util;

	/**
	* Private implementation class for EnumSet, for "regular sized" enum types
	* (i.e., those with 64 or fewer enum constants).
	*
	* @author Josh Bloch
	* @since 1.5
	* @serial exclude
	*/
	class RegularEnumSet<E extends Enum<E>> extends EnumSet<E> {
	@java.io.Serial
	private static final long serialVersionUID = 3411599620347842686L;
	/**
	* Bit vector representation of this set. The 2^k bit indicates the
	* presence of universe[k] in this set.
	*/
	private long elements = 0L;

	RegularEnumSet(Class<E>elementType, Enum<?>[] universe) {
	super(elementType, universe);
	}

	void addRange(E from, E to) {
	elements = (-1L >>> (from.ordinal() - to.ordinal() - 1)) << from.ordinal();
	}

	void addAll() {
	if (universe.length != 0)
	elements = -1L >>> -universe.length;
	}

	void complement() {
	if (universe.length != 0) {
	elements = ~elements;
	elements &= -1L >>> -universe.length; // Mask unused bits
	}
	}

	/**
	* Returns an iterator over the elements contained in this set. The
	* iterator traverses the elements in their <i>natural order</i> (which is
	* the order in which the enum constants are declared). The returned
	* Iterator is a "snapshot" iterator that will never throw {@link
	* ConcurrentModificationException}; the elements are traversed as they
	* existed when this call was invoked.
	*
	* @return an iterator over the elements contained in this set
	*/
	public Iterator<E> iterator() {
	return new EnumSetIterator<>();
	}

	private class EnumSetIterator<E extends Enum<E>> implements Iterator<E> {
	/**
	* A bit vector representing the elements in the set not yet
	* returned by this iterator.
	*/
	long unseen;

	/**
	* The bit representing the last element returned by this iterator
	* but not removed, or zero if no such element exists.
	*/
	long lastReturned = 0;

	EnumSetIterator() {
	unseen = elements;
	}

	public boolean hasNext() {
	return unseen != 0;
	}

	@SuppressWarnings("unchecked")
	public E next() {
	if (unseen == 0)
	throw new NoSuchElementException();
	lastReturned = unseen & -unseen;
	unseen -= lastReturned;
	return (E) universe[Long.numberOfTrailingZeros(lastReturned)];
	}

	public void remove() {
	if (lastReturned == 0)
	throw new IllegalStateException();
	elements &= ~lastReturned;
	lastReturned = 0;
	}
	}

	/**
	* Returns the number of elements in this set.
	*
	* @return the number of elements in this set
	*/
	public int size() {
	return Long.bitCount(elements);
	}

	/**
	* Returns {@code true} if this set contains no elements.
	*
	* @return {@code true} if this set contains no elements
	*/
	public boolean isEmpty() {
	return elements == 0;
	}

	/**
	* Returns {@code true} if this set contains the specified element.
	*
	* @param e element to be checked for containment in this collection
	* @return {@code true} if this set contains the specified element
	*/
	public boolean contains(Object e) {
	if (e == null)
	return false;
	Class<?> eClass = e.getClass();
	if (eClass != elementType && eClass.getSuperclass() != elementType)
	return false;

	return (elements & (1L << ((Enum<?>)e).ordinal())) != 0;
	}

	// Modification Operations

	/**
	* Adds the specified element to this set if it is not already present.
	*
	* @param e element to be added to this set
	* @return {@code true} if the set changed as a result of the call
	*
	* @throws NullPointerException if {@code e} is null
	*/
	public boolean add(E e) {
	typeCheck(e);

	long oldElements = elements;
	elements \|= (1L << ((Enum<?>)e).ordinal());
	return elements != oldElements;
	}

	/**
	* Removes the specified element from this set if it is present.
	*
	* @param e element to be removed from this set, if present
	* @return {@code true} if the set contained the specified element
	*/
	public boolean remove(Object e) {
	if (e == null)
	return false;
	Class<?> eClass = e.getClass();
	if (eClass != elementType && eClass.getSuperclass() != elementType)
	return false;

	long oldElements = elements;
	elements &= ~(1L << ((Enum<?>)e).ordinal());
	return elements != oldElements;
	}

	// Bulk Operations

	/**
	* Returns {@code true} if this set contains all of the elements
	* in the specified collection.
	*
	* @param c collection to be checked for containment in this set
	* @return {@code true} if this set contains all of the elements
	* in the specified collection
	* @throws NullPointerException if the specified collection is null
	*/
	public boolean containsAll(Collection<?> c) {
	if (!(c instanceof RegularEnumSet<?> es))
	return super.containsAll(c);

	if (es.elementType != elementType)
	return es.isEmpty();

	return (es.elements & ~elements) == 0;
	}

	/**
	* Adds all of the elements in the specified collection to this set.
	*
	* @param c collection whose elements are to be added to this set
	* @return {@code true} if this set changed as a result of the call
	* @throws NullPointerException if the specified collection or any
	* of its elements are null
	*/
	public boolean addAll(Collection<? extends E> c) {
	if (!(c instanceof RegularEnumSet<?> es))
	return super.addAll(c);

	if (es.elementType != elementType) {
	if (es.isEmpty())
	return false;
	else
	throw new ClassCastException(
	es.elementType + " != " + elementType);
	}

	long oldElements = elements;
	elements \|= es.elements;
	return elements != oldElements;
	}

	/**
	* Removes from this set all of its elements that are contained in
	* the specified collection.
	*
	* @param c elements to be removed from this set
	* @return {@code true} if this set changed as a result of the call
	* @throws NullPointerException if the specified collection is null
	*/
	public boolean removeAll(Collection<?> c) {
	if (!(c instanceof RegularEnumSet<?> es))
	return super.removeAll(c);

	if (es.elementType != elementType)
	return false;

	long oldElements = elements;
	elements &= ~es.elements;
	return elements != oldElements;
	}

	/**
	* Retains only the elements in this set that are contained in the
	* specified collection.
	*
	* @param c elements to be retained in this set
	* @return {@code true} if this set changed as a result of the call
	* @throws NullPointerException if the specified collection is null
	*/
	public boolean retainAll(Collection<?> c) {
	if (!(c instanceof RegularEnumSet<?> es))
	return super.retainAll(c);

	if (es.elementType != elementType) {
	boolean changed = (elements != 0);
	elements = 0;
	return changed;
	}

	long oldElements = elements;
	elements &= es.elements;
	return elements != oldElements;
	}

	/**
	* Removes all of the elements from this set.
	*/
	public void clear() {
	elements = 0;
	}

	/**
	* Compares the specified object with this set for equality. Returns
	* {@code true} if the given object is also a set, the two sets have
	* the same size, and every member of the given set is contained in
	* this set.
	*
	* @param o object to be compared for equality with this set
	* @return {@code true} if the specified object is equal to this set
	*/
	public boolean equals(Object o) {
	if (!(o instanceof RegularEnumSet<?> es))
	return super.equals(o);

	if (es.elementType != elementType)
	return elements == 0 && es.elements == 0;
	return es.elements == elements;
	}
	}

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