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 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

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 * by Oracle in the LICENSE file that accompanied this code.

 *

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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

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 *

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package java.util;

import sun.misc.SharedSecrets;

/**

 * A specialized {@link Set} implementation for use with enum types.  All of

 * the elements in an enum set must come from a single enum type that is

 * specified, explicitly or implicitly, when the set is created.  Enum sets

 * are represented internally as bit vectors.  This representation is

 * extremely compact and efficient. The space and time performance of this

 * class should be good enough to allow its use as a high-quality, typesafe

 * alternative to traditional <tt>int</tt>-based "bit flags."  Even bulk

 * operations (such as <tt>containsAll</tt> and <tt>retainAll</tt>) should

 * run very quickly if their argument is also an enum set.

 *

 * <p>The iterator returned by the <tt>iterator</tt> method traverses the

 * elements in their <i>natural order</i> (the order in which the enum

 * constants are declared).  The returned iterator is <i>weakly

 * consistent</i>: it will never throw {@link ConcurrentModificationException}

 * and it may or may not show the effects of any modifications to the set that

 * occur while the iteration is in progress.

 *

 * <p>Null elements are not permitted.  Attempts to insert a null element

 * will throw {@link NullPointerException}.  Attempts to test for the

 * presence of a null element or to remove one will, however, function

 * properly.

 *

 * <P>Like most collection implementations, <tt>EnumSet</tt> is not

 * synchronized.  If multiple threads access an enum set concurrently, and at

 * least one of the threads modifies the set, it should be synchronized

 * externally.  This is typically accomplished by synchronizing on some

 * object that naturally encapsulates the enum set.  If no such object exists,

 * the set should be "wrapped" using the {@link Collections#synchronizedSet}

 * method.  This is best done at creation time, to prevent accidental

 * unsynchronized access:

 *

 * <pre>

 * Set<MyEnum> s = Collections.synchronizedSet(EnumSet.noneOf(MyEnum.class));

 * </pre>

 *

 * <p>Implementation note: All basic operations execute in constant time.

 * They are likely (though not guaranteed) to be much faster than their

 * {@link HashSet} counterparts.  Even bulk operations execute in

 * constant time if their argument is also an enum set.

 *

 * <p>This class is a member of the

 * <a href="{@docRoot}/../technotes/guides/collections/index.html">

 * Java Collections Framework</a>.

 *

 * @author Josh Bloch

 * @since 1.5

 * @see EnumMap

 * @serial exclude

 */

public abstract class EnumSet<E extends Enum<E>> extends AbstractSet<E>

    implements Cloneable, java.io.Serializable

{

    /**

     * The class of all the elements of this set.

     */

    final Class<E> elementType;

    /**

     * All of the values comprising T.  (Cached for performance.)

     */

    final Enum[] universe;

    private static Enum[] ZERO_LENGTH_ENUM_ARRAY = new Enum[0];

    EnumSet(Class<E>elementType, Enum[] universe) {

        this.elementType = elementType;

        this.universe    = universe;

    }

    /**

     * Creates an empty enum set with the specified element type.

     *

     * @param elementType the class object of the element type for this enum

     *     set

     * @throws NullPointerException if <tt>elementType</tt> is null

     */

    public static <E extends Enum<E>> EnumSet<E> noneOf(Class<E> elementType) {

        Enum[] universe = getUniverse(elementType);

        if (universe == null)

            throw new ClassCastException(elementType + " not an enum");

        if (universe.length <= 64)

            return new RegularEnumSet<>(elementType, universe);

        else

            return new JumboEnumSet<>(elementType, universe);

    }

    /**

     * Creates an enum set containing all of the elements in the specified

     * element type.

     *

     * @param elementType the class object of the element type for this enum

     *     set

     * @throws NullPointerException if <tt>elementType</tt> is null

     */

    public static <E extends Enum<E>> EnumSet<E> allOf(Class<E> elementType) {

        EnumSet<E> result = noneOf(elementType);

        result.addAll();

        return result;

    }

    /**

     * Adds all of the elements from the appropriate enum type to this enum

     * set, which is empty prior to the call.

     */

    abstract void addAll();

    /**

     * Creates an enum set with the same element type as the specified enum

     * set, initially containing the same elements (if any).

     *

     * @param s the enum set from which to initialize this enum set

     * @throws NullPointerException if <tt>s</tt> is null

     */

    public static <E extends Enum<E>> EnumSet<E> copyOf(EnumSet<E> s) {

        return s.clone();

    }

    /**

     * Creates an enum set initialized from the specified collection.  If

     * the specified collection is an <tt>EnumSet</tt> instance, this static

     * factory method behaves identically to {@link #copyOf(EnumSet)}.

     * Otherwise, the specified collection must contain at least one element

     * (in order to determine the new enum set's element type).

     *

     * @param c the collection from which to initialize this enum set

     * @throws IllegalArgumentException if <tt>c</tt> is not an

     *     <tt>EnumSet</tt> instance and contains no elements

     * @throws NullPointerException if <tt>c</tt> is null

     */

    public static <E extends Enum<E>> EnumSet<E> copyOf(Collection<E> c) {

        if (c instanceof EnumSet) {

            return ((EnumSet<E>)c).clone();

        } else {

            if (c.isEmpty())

                throw new IllegalArgumentException("Collection is empty");

            Iterator<E> i = c.iterator();

            E first = i.next();

            EnumSet<E> result = EnumSet.of(first);

            while (i.hasNext())

                result.add(i.next());

            return result;

        }

    }

    /**

     * Creates an enum set with the same element type as the specified enum

     * set, initially containing all the elements of this type that are

     * <i>not</i> contained in the specified set.

     *

     * @param s the enum set from whose complement to initialize this enum set

     * @throws NullPointerException if <tt>s</tt> is null

     */

    public static <E extends Enum<E>> EnumSet<E> complementOf(EnumSet<E> s) {

        EnumSet<E> result = copyOf(s);

        result.complement();

        return result;

    }

    /**

     * Creates an enum set initially containing the specified element.

     *

     * Overloadings of this method exist to initialize an enum set with

     * one through five elements.  A sixth overloading is provided that

     * uses the varargs feature.  This overloading may be used to create

     * an enum set initially containing an arbitrary number of elements, but

     * is likely to run slower than the overloadings that do not use varargs.

     *

     * @param e the element that this set is to contain initially

     * @throws NullPointerException if <tt>e</tt> is null

     * @return an enum set initially containing the specified element

     */

    public static <E extends Enum<E>> EnumSet<E> of(E e) {

        EnumSet<E> result = noneOf(e.getDeclaringClass());

        result.add(e);

        return result;

    }

    /**

     * Creates an enum set initially containing the specified elements.

     *

     * Overloadings of this method exist to initialize an enum set with

     * one through five elements.  A sixth overloading is provided that

     * uses the varargs feature.  This overloading may be used to create

     * an enum set initially containing an arbitrary number of elements, but

     * is likely to run slower than the overloadings that do not use varargs.

     *

     * @param e1 an element that this set is to contain initially

     * @param e2 another element that this set is to contain initially

     * @throws NullPointerException if any parameters are null

     * @return an enum set initially containing the specified elements

     */

    public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2) {

        EnumSet<E> result = noneOf(e1.getDeclaringClass());

        result.add(e1);

        result.add(e2);

        return result;

    }

    /**

     * Creates an enum set initially containing the specified elements.

     *

     * Overloadings of this method exist to initialize an enum set with

     * one through five elements.  A sixth overloading is provided that

     * uses the varargs feature.  This overloading may be used to create

     * an enum set initially containing an arbitrary number of elements, but

     * is likely to run slower than the overloadings that do not use varargs.

     *

     * @param e1 an element that this set is to contain initially

     * @param e2 another element that this set is to contain initially

     * @param e3 another element that this set is to contain initially

     * @throws NullPointerException if any parameters are null

     * @return an enum set initially containing the specified elements

     */

    public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2, E e3) {

        EnumSet<E> result = noneOf(e1.getDeclaringClass());

        result.add(e1);

        result.add(e2);

        result.add(e3);

        return result;

    }

    /**

     * Creates an enum set initially containing the specified elements.

     *

     * Overloadings of this method exist to initialize an enum set with

     * one through five elements.  A sixth overloading is provided that

     * uses the varargs feature.  This overloading may be used to create

     * an enum set initially containing an arbitrary number of elements, but

     * is likely to run slower than the overloadings that do not use varargs.

     *

     * @param e1 an element that this set is to contain initially

     * @param e2 another element that this set is to contain initially

     * @param e3 another element that this set is to contain initially

     * @param e4 another element that this set is to contain initially

     * @throws NullPointerException if any parameters are null

     * @return an enum set initially containing the specified elements

     */

    public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2, E e3, E e4) {

        EnumSet<E> result = noneOf(e1.getDeclaringClass());

        result.add(e1);

        result.add(e2);

        result.add(e3);

        result.add(e4);

        return result;

    }

    /**

     * Creates an enum set initially containing the specified elements.

     *

     * Overloadings of this method exist to initialize an enum set with

     * one through five elements.  A sixth overloading is provided that

     * uses the varargs feature.  This overloading may be used to create

     * an enum set initially containing an arbitrary number of elements, but

     * is likely to run slower than the overloadings that do not use varargs.

     *

     * @param e1 an element that this set is to contain initially

     * @param e2 another element that this set is to contain initially

     * @param e3 another element that this set is to contain initially

     * @param e4 another element that this set is to contain initially

     * @param e5 another element that this set is to contain initially

     * @throws NullPointerException if any parameters are null

     * @return an enum set initially containing the specified elements

     */

    public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2, E e3, E e4,

                                                    E e5)

    {

        EnumSet<E> result = noneOf(e1.getDeclaringClass());

        result.add(e1);

        result.add(e2);

        result.add(e3);

        result.add(e4);

        result.add(e5);

        return result;

    }

    /**

     * Creates an enum set initially containing the specified elements.

     * This factory, whose parameter list uses the varargs feature, may

     * be used to create an enum set initially containing an arbitrary

     * number of elements, but it is likely to run slower than the overloadings

     * that do not use varargs.

     *

     * @param first an element that the set is to contain initially

     * @param rest the remaining elements the set is to contain initially

     * @throws NullPointerException if any of the specified elements are null,

     *     or if <tt>rest</tt> is null

     * @return an enum set initially containing the specified elements

     */

    @SafeVarargs

    public static <E extends Enum<E>> EnumSet<E> of(E first, E... rest) {

        EnumSet<E> result = noneOf(first.getDeclaringClass());

        result.add(first);

        for (E e : rest)

            result.add(e);

        return result;

    }

    /**

     * Creates an enum set initially containing all of the elements in the

     * range defined by the two specified endpoints.  The returned set will

     * contain the endpoints themselves, which may be identical but must not

     * be out of order.

     *

     * @param from the first element in the range

     * @param to the last element in the range

     * @throws NullPointerException if {@code from} or {@code to} are null

     * @throws IllegalArgumentException if {@code from.compareTo(to) > 0}

     * @return an enum set initially containing all of the elements in the

     *         range defined by the two specified endpoints

     */

    public static <E extends Enum<E>> EnumSet<E> range(E from, E to) {

        if (from.compareTo(to) > 0)

            throw new IllegalArgumentException(from + " > " + to);

        EnumSet<E> result = noneOf(from.getDeclaringClass());

        result.addRange(from, to);

        return result;

    }

    /**

     * Adds the specified range to this enum set, which is empty prior

     * to the call.

     */

    abstract void addRange(E from, E to);

    /**

     * Returns a copy of this set.

     *

     * @return a copy of this set

     */

    public EnumSet<E> clone() {

        try {

            return (EnumSet<E>) super.clone();

        } catch(CloneNotSupportedException e) {

            throw new AssertionError(e);

        }

    }

    /**

     * Complements the contents of this enum set.

     */

    abstract void complement();

    /**

     * Throws an exception if e is not of the correct type for this enum set.

     */

    final void typeCheck(E e) {

        Class eClass = e.getClass();

        if (eClass != elementType && eClass.getSuperclass() != elementType)

            throw new ClassCastException(eClass + " != " + elementType);

    }

    /**

     * Returns all of the values comprising E.

     * The result is uncloned, cached, and shared by all callers.

     */

    private static <E extends Enum<E>> E[] getUniverse(Class<E> elementType) {

        return SharedSecrets.getJavaLangAccess()

                                        .getEnumConstantsShared(elementType);

    }

    /**

     * This class is used to serialize all EnumSet instances, regardless of

     * implementation type.  It captures their "logical contents" and they

     * are reconstructed using public static factories.  This is necessary

     * to ensure that the existence of a particular implementation type is

     * an implementation detail.

     *

     * @serial include

     */

    private static class SerializationProxy <E extends Enum<E>>

        implements java.io.Serializable

    {

        /**

         * The element type of this enum set.

         *

         * @serial

         */

        private final Class<E> elementType;

        /**

         * The elements contained in this enum set.

         *

         * @serial

         */

        private final Enum[] elements;

        SerializationProxy(EnumSet<E> set) {

            elementType = set.elementType;

            elements = set.toArray(ZERO_LENGTH_ENUM_ARRAY);

        }

        private Object readResolve() {

            EnumSet<E> result = EnumSet.noneOf(elementType);

            for (Enum e : elements)

                result.add((E)e);

            return result;

        }

        private static final long serialVersionUID = 362491234563181265L;

    }

    Object writeReplace() {

        return new SerializationProxy<>(this);

    }

    // readObject method for the serialization proxy pattern

    // See Effective Java, Second Ed., Item 78.

    private void readObject(java.io.ObjectInputStream stream)

        throws java.io.InvalidObjectException {

        throw new java.io.InvalidObjectException("Proxy required");

    }

}