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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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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
 * 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.
 *
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package java.util.stream;

import java.util.Iterator;
import java.util.Spliterator;

/**
 * Base interface for stream types such as {@link Stream}, {@link IntStream},
 * etc.  Contains methods common to all stream types.  Many of these methods
 * are implemented by {@link AbstractPipeline}, even though
 * {@code AbstractPipeline} does not directly implement {@code BaseStream}.
 *
 * @param <T> type of stream elements
 * @param <S> type of stream implementing {@code BaseStream}
 * @since 1.8
 */
interface BaseStream<T, S extends BaseStream<T, S>> {
    /**
     * Returns an iterator for the elements of this stream.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return the element iterator for this stream
     */
    Iterator<T> iterator();

    /**
     * Returns a spliterator for the elements of this stream.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return the element spliterator for this stream
     */
    Spliterator<T> spliterator();

    /**
     * Returns whether this stream, when executed, would execute in parallel
     * (assuming no further modification of the stream, such as appending
     * further intermediate operations or changing its parallelism).  Calling
     * this method after invoking an intermediate or terminal stream operation
     * method may yield unpredictable results.
     *
     * @return {@code true} if this stream would execute in parallel if executed
     * without further modification otherwise {@code false}
     */
    boolean isParallel();

    /**
     * Returns an equivalent stream that is sequential.  May return
     * itself, either because the stream was already sequential, or because
     * the underlying stream state was modified to be sequential.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @return a sequential stream
     */
    S sequential();

    /**
     * Returns an equivalent stream that is parallel.  May return
     * itself, either because the stream was already parallel, or because
     * the underlying stream state was modified to be parallel.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @return a parallel stream
     */
    S parallel();

    /**
     * Returns an equivalent stream that is
     * <a href="package-summary.html#Ordering">unordered</a>.  May return
     * itself if the stream was already unordered.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @return an unordered stream
     */
    S unordered();
}