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fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists, and queues with a small memory footprint and fast access and insertion; it provides also big (64-bit) arrays, sets and lists, sorting algorithms, fast, practical I/O classes for binary and text files, and facilities for memory mapping large files. Note that if you have both this jar and fastutil-core.jar in your dependencies, fastutil-core.jar should be excluded.

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/*
	* Copyright (C) 2002-2022 Sebastiano Vigna
	*
	* Licensed 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 it.unimi.dsi.fastutil.objects;

import java.util.Collection;
import static it.unimi.dsi.fastutil.Size64.sizeOf;

/**
 * A type-specific {@link Collection}; provides some additional methods that use polymorphism to
 * avoid (un)boxing.
 *
 * 
 * Additionally, this class defines strengthens (again) {@link #iterator()}.
 *
 * @see Collection
 */
public interface ReferenceCollection extends Collection, ObjectIterable {
	/**
	 * Returns a type-specific iterator on the elements of this collection.
	 *
	 * @apiNote This specification strengthens the one given in {@link java.lang.Iterable#iterator()},
	 *          which was already strengthened in the corresponding type-specific class, but was
	 *          weakened by the fact that this interface extends {@link Collection}.
	 *
	 * @return a type-specific iterator on the elements of this collection.
	 */
	@Override
	ObjectIterator iterator();

	// If you change these default spliterator methods, you will likely need to update Iterable, List,
	// Set, and SortedSet too
	/**
	 * Returns a type-specific spliterator on the elements of this collection.
	 *
	 * 

	 * See {@link java.util.Collection#spliterator()} for more documentation on the requirements of the
	 * returned spliterator.
	 *
	 * @apiNote This specification strengthens the one given in
	 *          {@link java.util.Collection#spliterator()}.
	 *          

	 *          Also, this is generally the only {@code spliterator} method subclasses should override.
	 *
	 * @implSpec The default implementation returns a late-binding spliterator (see
	 *           {@link java.util.Spliterator Spliterator} for documentation on what binding policies
	 *           mean) that wraps this instance's type specific {@link #iterator}.
	 *           
	 *           Additionally, it reports {@link java.util.Spliterator#SIZED Spliterator.SIZED}
	 *
	 * @implNote As this default implementation wraps the iterator, and {@link java.util.Iterator} is an
	 *           inherently linear API, the returned spliterator will yield limited performance gains
	 *           when run in parallel contexts, as the returned spliterator's
	 *           {@link java.util.Spliterator#trySplit() trySplit()} will have linear runtime.
	 *
	 * @return a type-specific spliterator on the elements of this collection.
	 * @since 8.5.0
	 */
	@Override
	default ObjectSpliterator spliterator() {
		return ObjectSpliterators.asSpliterator(iterator(), sizeOf(this), ObjectSpliterators.COLLECTION_SPLITERATOR_CHARACTERISTICS);
	}
}