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 * 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,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java8.util.stream;

import java8.util.LongSummaryStatistics;
import java8.util.PrimitiveIterator;
import java8.util.function.BiConsumer;
import java8.util.function.Function;
import java8.util.function.LongBinaryOperator;
import java8.util.function.LongConsumer;
import java8.util.function.LongFunction;
import java8.util.function.LongPredicate;
import java8.util.function.LongSupplier;
import java8.util.function.LongToDoubleFunction;
import java8.util.function.LongToIntFunction;
import java8.util.function.LongUnaryOperator;
import java8.util.function.ObjLongConsumer;
import java8.util.function.Supplier;
import java8.util.OptionalDouble;
import java8.util.OptionalLong;
import java8.util.Spliterator;

/**
 * A sequence of primitive long-valued elements supporting sequential and parallel
 * aggregate operations.  This is the {@code long} primitive specialization of
 * {@link Stream}.
 *
 * <p>The following example illustrates an aggregate operation using
 * {@link Stream} and {@link LongStream}, computing the sum of the weights of the
 * red widgets:
 *
 * <pre>{@code
 *     long sum = widgets.stream()
 *                       .filter(w -> w.getColor() == RED)
 *                       .mapToLong(w -> w.getWeight())
 *                       .sum();
 * }</pre>
 *
 * See the class documentation for {@link Stream} and the package documentation
 * for <a href="package-summary.html">java8.util.stream</a> for additional
 * specification of streams, stream operations, stream pipelines, and
 * parallelism.
 *
 * @since 1.8
 * @see Stream
 * @see <a href="package-summary.html">java8.util.stream</a>
 */
public interface LongStream extends BaseStream<Long, LongStream> {

    /**
     * Returns a stream consisting of the elements of this stream that match
     * the given predicate.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to each element to determine if it
     *                  should be included
     * @return the new stream
     */
    LongStream filter(LongPredicate predicate);

    /**
     * Returns a stream consisting of the results of applying the given
     * function to the elements of this stream.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *               <a href="package-summary.html#Statelessness">stateless</a>
     *               function to apply to each element
     * @return the new stream
     */
    LongStream map(LongUnaryOperator mapper);

    /**
     * Returns an object-valued {@code Stream} consisting of the results of
     * applying the given function to the elements of this stream.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">
     *     intermediate operation</a>.
     *
     * @param <U> the element type of the new stream
     * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *               <a href="package-summary.html#Statelessness">stateless</a>
     *               function to apply to each element
     * @return the new stream
     */
    <U> Stream<U> mapToObj(LongFunction<? extends U> mapper);

    /**
     * Returns an {@code IntStream} consisting of the results of applying the
     * given function to the elements of this stream.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *               <a href="package-summary.html#Statelessness">stateless</a>
     *               function to apply to each element
     * @return the new stream
     */
    IntStream mapToInt(LongToIntFunction mapper);

    /**
     * Returns a {@code DoubleStream} consisting of the results of applying the
     * given function to the elements of this stream.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *               <a href="package-summary.html#Statelessness">stateless</a>
     *               function to apply to each element
     * @return the new stream
     */
    DoubleStream mapToDouble(LongToDoubleFunction mapper);

    /**
     * Returns a stream consisting of the results of replacing each element of
     * this stream with the contents of a mapped stream produced by applying
     * the provided mapping function to each element.  Each mapped stream is
     * {@link java8.util.stream.BaseStream#close() closed} after its contents
     * have been placed into this stream.  (If a mapped stream is {@code null}
     * an empty stream is used, instead.)
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *               <a href="package-summary.html#Statelessness">stateless</a>
     *               function to apply to each element which produces a
     *               {@code LongStream} of new values
     * @return the new stream
     * @see Stream#flatMap(Function)
     */
    LongStream flatMap(LongFunction<? extends LongStream> mapper);

    /**
     * Returns a stream consisting of the distinct elements of this stream.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">stateful
     * intermediate operation</a>.
     *
     * @return the new stream
     */
    LongStream distinct();

    /**
     * Returns a stream consisting of the elements of this stream in sorted
     * order.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">stateful
     * intermediate operation</a>.
     *
     * @return the new stream
     */
    LongStream sorted();

    /**
     * Returns a stream consisting of the elements of this stream, additionally
     * performing the provided action on each element as elements are consumed
     * from the resulting stream.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * <p>For parallel stream pipelines, the action may be called at
     * whatever time and in whatever thread the element is made available by the
     * upstream operation.  If the action modifies shared state,
     * it is responsible for providing the required synchronization.
     *
     * <p><b>API Note:</b><br> This method exists mainly to support debugging, where you want
     * to see the elements as they flow past a certain point in a pipeline:
     * <pre>{@code
     *     LongStreams.of(1, 2, 3, 4)
     *         .filter(e -> e > 2)
     *         .peek(e -> System.out.println("Filtered value: " + e))
     *         .map(e -> e * e)
     *         .peek(e -> System.out.println("Mapped value: " + e))
     *         .sum();
     * }</pre>
     *
     * <p>In cases where the stream implementation is able to optimize away the
     * production of some or all the elements (such as with short-circuiting
     * operations like {@code findFirst}, or in the example described in
     * {@link #count}), the action will not be invoked for those elements.
     *
     * @param action a <a href="package-summary.html#NonInterference">
     *               non-interfering</a> action to perform on the elements as
     *               they are consumed from the stream
     * @return the new stream
     */
    LongStream peek(LongConsumer action);

    /**
     * Returns a stream consisting of the elements of this stream, truncated
     * to be no longer than {@code maxSize} in length.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * stateful intermediate operation</a>.
     *
     * <p><b>API Note:</b><br>
     * While {@code limit()} is generally a cheap operation on sequential
     * stream pipelines, it can be quite expensive on ordered parallel pipelines,
     * especially for large values of {@code maxSize}, since {@code limit(n)}
     * is constrained to return not just any <em>n</em> elements, but the
     * <em>first n</em> elements in the encounter order.  Using an unordered
     * stream source (such as {@link LongStreams#generate(LongSupplier)}) or removing the
     * ordering constraint with {@link #unordered()} may result in significant
     * speedups of {@code limit()} in parallel pipelines, if the semantics of
     * your situation permit.  If consistency with encounter order is required,
     * and you are experiencing poor performance or memory utilization with
     * {@code limit()} in parallel pipelines, switching to sequential execution
     * with {@link #sequential()} may improve performance.
     *
     * @param maxSize the number of elements the stream should be limited to
     * @return the new stream
     * @throws IllegalArgumentException if {@code maxSize} is negative
     */
    LongStream limit(long maxSize);

    /**
     * Returns a stream consisting of the remaining elements of this stream
     * after discarding the first {@code n} elements of the stream.
     * If this stream contains fewer than {@code n} elements then an
     * empty stream will be returned.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">stateful
     * intermediate operation</a>.
     *
     * <p><b>API Note:</b><br>
     * While {@code skip()} is generally a cheap operation on sequential
     * stream pipelines, it can be quite expensive on ordered parallel pipelines,
     * especially for large values of {@code n}, since {@code skip(n)}
     * is constrained to skip not just any <em>n</em> elements, but the
     * <em>first n</em> elements in the encounter order.  Using an unordered
     * stream source (such as {@link LongStreams#generate(LongSupplier)}) or removing the
     * ordering constraint with {@link #unordered()} may result in significant
     * speedups of {@code skip()} in parallel pipelines, if the semantics of
     * your situation permit.  If consistency with encounter order is required,
     * and you are experiencing poor performance or memory utilization with
     * {@code skip()} in parallel pipelines, switching to sequential execution
     * with {@link #sequential()} may improve performance.
     *
     * @param n the number of leading elements to skip
     * @return the new stream
     * @throws IllegalArgumentException if {@code n} is negative
     */
    LongStream skip(long n);

    /**
     * Returns, if this stream is ordered, a stream consisting of the longest
     * prefix of elements taken from this stream that match the given predicate.
     * Otherwise returns, if this stream is unordered, a stream consisting of a
     * subset of elements taken from this stream that match the given predicate.
     *
     * <p>If this stream is ordered then the longest prefix is a contiguous
     * sequence of elements of this stream that match the given predicate.  The
     * first element of the sequence is the first element of this stream, and
     * the element immediately following the last element of the sequence does
     * not match the given predicate.
     *
     * <p>If this stream is unordered, and some (but not all) elements of this
     * stream match the given predicate, then the behavior of this operation is
     * nondeterministic; it is free to take any subset of matching elements
     * (which includes the empty set).
     *
     * <p>Independent of whether this stream is ordered or unordered if all
     * elements of this stream match the given predicate then this operation
     * takes all elements (the result is the same as the input), or if no
     * elements of the stream match the given predicate then no elements are
     * taken (the result is an empty stream).
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * stateful intermediate operation</a>.
     *
     * <p><b>Implementation Requirements:</b><br>
     * The default implementation obtains the {@link #spliterator() spliterator}
     * of this stream, wraps that spliterator so as to support the semantics
     * of this operation on traversal, and returns a new stream associated with
     * the wrapped spliterator.  The returned stream preserves the execution
     * characteristics of this stream (namely parallel or sequential execution
     * as per {@link #isParallel()}) but the wrapped spliterator may choose to
     * not support splitting. When the returned stream is closed, the close
     * handlers for both the returned and this stream are invoked.
     *
     * <p><b>API Note:</b><br>
     * While {@code takeWhile()} is generally a cheap operation on sequential
     * stream pipelines, it can be quite expensive on ordered parallel
     * pipelines, since the operation is constrained to return not just any
     * valid prefix, but the longest prefix of elements in the encounter order.
     * Using an unordered stream source (such as
     * {@link LongStreams#generate(LongSupplier)}) or removing the ordering constraint with
     * {@link #unordered()} may result in significant speedups of
     * {@code takeWhile()} in parallel pipelines, if the semantics of your
     * situation permit.  If consistency with encounter order is required, and
     * you are experiencing poor performance or memory utilization with
     * {@code takeWhile()} in parallel pipelines, switching to sequential
     * execution with {@link #sequential()} may improve performance.
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to elements to determine the longest
     *                  prefix of elements.
     * @return the new stream
     * @since 9
     */
    LongStream takeWhile(LongPredicate predicate);

    /**
     * Returns, if this stream is ordered, a stream consisting of the remaining
     * elements of this stream after dropping the longest prefix of elements
     * that match the given predicate.  Otherwise returns, if this stream is
     * unordered, a stream consisting of the remaining elements of this stream
     * after dropping a subset of elements that match the given predicate.
     *
     * <p>If this stream is ordered then the longest prefix is a contiguous
     * sequence of elements of this stream that match the given predicate.  The
     * first element of the sequence is the first element of this stream, and
     * the element immediately following the last element of the sequence does
     * not match the given predicate.
     *
     * <p>If this stream is unordered, and some (but not all) elements of this
     * stream match the given predicate, then the behavior of this operation is
     * nondeterministic; it is free to drop any subset of matching elements
     * (which includes the empty set).
     *
     * <p>Independent of whether this stream is ordered or unordered if all
     * elements of this stream match the given predicate then this operation
     * drops all elements (the result is an empty stream), or if no elements of
     * the stream match the given predicate then no elements are dropped (the
     * result is the same as the input).
     *
     * <p>This is a <a href="package-summary.html#StreamOps">stateful
     * intermediate operation</a>.
     *
     * <p><b>Implementation Requirements:</b><br>
     * The default implementation obtains the {@link #spliterator() spliterator}
     * of this stream, wraps that spliterator so as to support the semantics
     * of this operation on traversal, and returns a new stream associated with
     * the wrapped spliterator.  The returned stream preserves the execution
     * characteristics of this stream (namely parallel or sequential execution
     * as per {@link #isParallel()}) but the wrapped spliterator may choose to
     * not support splitting. When the returned stream is closed, the close
     * handlers for both the returned and this stream are invoked.
     *
     * <p><b>API Note:</b><br>
     * While {@code dropWhile()} is generally a cheap operation on sequential
     * stream pipelines, it can be quite expensive on ordered parallel
     * pipelines, since the operation is constrained to return not just any
     * valid prefix, but the longest prefix of elements in the encounter order.
     * Using an unordered stream source (such as
     * {@link LongStreams#generate(LongSupplier)}) or removing the ordering constraint with
     * {@link #unordered()} may result in significant speedups of
     * {@code dropWhile()} in parallel pipelines, if the semantics of your
     * situation permit.  If consistency with encounter order is required, and
     * you are experiencing poor performance or memory utilization with
     * {@code dropWhile()} in parallel pipelines, switching to sequential
     * execution with {@link #sequential()} may improve performance.
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to elements to determine the longest
     *                  prefix of elements.
     * @return the new stream
     * @since 9
     */
    LongStream dropWhile(LongPredicate predicate);

    /**
     * Performs an action for each element of this stream.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * <p>For parallel stream pipelines, this operation does <em>not</em>
     * guarantee to respect the encounter order of the stream, as doing so
     * would sacrifice the benefit of parallelism.  For any given element, the
     * action may be performed at whatever time and in whatever thread the
     * library chooses.  If the action accesses shared state, it is
     * responsible for providing the required synchronization.
     *
     * @param action a <a href="package-summary.html#NonInterference">
     *               non-interfering</a> action to perform on the elements
     */
    void forEach(LongConsumer action);

    /**
     * Performs an action for each element of this stream, guaranteeing that
     * each element is processed in encounter order for streams that have a
     * defined encounter order.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @param action a <a href="package-summary.html#NonInterference">
     *               non-interfering</a> action to perform on the elements
     * @see #forEach(LongConsumer)
     */
    void forEachOrdered(LongConsumer action);

    /**
     * Returns an array containing the elements of this stream.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return an array containing the elements of this stream
     */
    long[] toArray();

    /**
     * Performs a <a href="package-summary.html#Reduction">reduction</a> on the
     * elements of this stream, using the provided identity value and an
     * <a href="package-summary.html#Associativity">associative</a>
     * accumulation function, and returns the reduced value.  This is equivalent
     * to:
     * <pre>{@code
     *     long result = identity;
     *     for (long element : this stream)
     *         result = accumulator.applyAsLong(result, element)
     *     return result;
     * }</pre>
     *
     * but is not constrained to execute sequentially.
     *
     * <p>The {@code identity} value must be an identity for the accumulator
     * function. This means that for all {@code x},
     * {@code accumulator.apply(identity, x)} is equal to {@code x}.
     * The {@code accumulator} function must be an
     * <a href="package-summary.html#Associativity">associative</a> function.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * <p><b>API Note:</b><br> Sum, min, max, and average are all special cases of reduction.
     * Summing a stream of numbers can be expressed as:
     *
     * <pre>{@code
     *     long sum = integers.reduce(0, (a, b) -> a+b);
     * }</pre>
     *
     * or more compactly:
     *
     * <pre>{@code
     *     long sum = integers.reduce(0, Long::sum);
     * }</pre>
     *
     * <p>While this may seem a more roundabout way to perform an aggregation
     * compared to simply mutating a running total in a loop, reduction
     * operations parallelize more gracefully, without needing additional
     * synchronization and with greatly reduced risk of data races.
     *
     * @param identity the identity value for the accumulating function
     * @param op an <a href="package-summary.html#Associativity">associative</a>,
     *           <a href="package-summary.html#NonInterference">non-interfering</a>,
     *           <a href="package-summary.html#Statelessness">stateless</a>
     *           function for combining two values
     * @return the result of the reduction
     * @see #sum()
     * @see #min()
     * @see #max()
     * @see #average()
     */
    long reduce(long identity, LongBinaryOperator op);

    /**
     * Performs a <a href="package-summary.html#Reduction">reduction</a> on the
     * elements of this stream, using an
     * <a href="package-summary.html#Associativity">associative</a> accumulation
     * function, and returns an {@code OptionalLong} describing the reduced value,
     * if any. This is equivalent to:
     * <pre>{@code
     *     boolean foundAny = false;
     *     long result = null;
     *     for (long element : this stream) {
     *         if (!foundAny) {
     *             foundAny = true;
     *             result = element;
     *         }
     *         else
     *             result = accumulator.applyAsLong(result, element);
     *     }
     *     return foundAny ? OptionalLong.of(result) : OptionalLong.empty();
     * }</pre>
     *
     * but is not constrained to execute sequentially.
     *
     * <p>The {@code accumulator} function must be an
     * <a href="package-summary.html#Associativity">associative</a> function.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @param op an <a href="package-summary.html#Associativity">associative</a>,
     *           <a href="package-summary.html#NonInterference">non-interfering</a>,
     *           <a href="package-summary.html#Statelessness">stateless</a>
     *           function for combining two values
     * @return the result of the reduction
     * @see #reduce(long, LongBinaryOperator)
     */
    OptionalLong reduce(LongBinaryOperator op);

    /**
     * Performs a <a href="package-summary.html#MutableReduction">mutable
     * reduction</a> operation on the elements of this stream.  A mutable
     * reduction is one in which the reduced value is a mutable result container,
     * such as an {@code ArrayList}, and elements are incorporated by updating
     * the state of the result rather than by replacing the result.  This
     * produces a result equivalent to:
     * <pre>{@code
     *     R result = supplier.get();
     *     for (long element : this stream)
     *         accumulator.accept(result, element);
     *     return result;
     * }</pre>
     *
     * <p>Like {@link #reduce(long, LongBinaryOperator)}, {@code collect} operations
     * can be parallelized without requiring additional synchronization.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @param <R> the type of the mutable result container
     * @param supplier a function that creates a new mutable result container.
     *                 For a parallel execution, this function may be called
     *                 multiple times and must return a fresh value each time
     * @param accumulator an <a href="package-summary.html#Associativity">associative</a>,
     *                    <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                    <a href="package-summary.html#Statelessness">stateless</a>
     *                    function that must fold an element into a result
     *                    container
     * @param combiner an <a href="package-summary.html#Associativity">associative</a>,
     *                    <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                    <a href="package-summary.html#Statelessness">stateless</a>
     *                    function that accepts two partial result containers
     *                    and merges them, which must be compatible with the
     *                    accumulator function.  The combiner function must fold
     *                    the elements from the second result container into the
     *                    first result container
     * @return the result of the reduction
     * @see Stream#collect(Supplier, BiConsumer, BiConsumer)
     */
    <R> R collect(Supplier<R> supplier,
                  ObjLongConsumer<R> accumulator,
                  BiConsumer<R, R> combiner);

    /**
     * Returns the sum of elements in this stream.  This is a special case
     * of a <a href="package-summary.html#Reduction">reduction</a>
     * and is equivalent to:
     * <pre>{@code
     *     return reduce(0, Long::sum);
     * }</pre>
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return the sum of elements in this stream
     */
    long sum();

    /**
     * Returns an {@code OptionalLong} describing the minimum element of this
     * stream, or an empty optional if this stream is empty.  This is a special
     * case of a <a href="package-summary.html#Reduction">reduction</a>
     * and is equivalent to:
     * <pre>{@code
     *     return reduce(Long::min);
     * }</pre>
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>.
     *
     * @return an {@code OptionalLong} containing the minimum element of this
     * stream, or an empty {@code OptionalLong} if the stream is empty
     */
    OptionalLong min();

    /**
     * Returns an {@code OptionalLong} describing the maximum element of this
     * stream, or an empty optional if this stream is empty.  This is a special
     * case of a <a href="package-summary.html#Reduction">reduction</a>
     * and is equivalent to:
     * <pre>{@code
     *     return reduce(Long::max);
     * }</pre>
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return an {@code OptionalLong} containing the maximum element of this
     * stream, or an empty {@code OptionalLong} if the stream is empty
     */
    OptionalLong max();

    /**
     * Returns the count of elements in this stream.  This is a special case of
     * a <a href="package-summary.html#Reduction">reduction</a> and is (at least
     * in the predominant case where the count can't be directly obtained from
     * the stream source) equivalent to:
     * <pre>{@code
     *     return map(e -> 1L).sum();
     * }</pre>
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>.
     *
     * <p><b>API Note:</b><br>
     * An implementation may choose to not execute the stream pipeline (either
     * sequentially or in parallel) if it is capable of computing the count
     * directly from the stream source.  In such cases no source elements will
     * be traversed and no intermediate operations will be evaluated.
     * Behavioral parameters with side-effects, which are strongly discouraged
     * except for harmless cases such as debugging, may be affected.  For
     * example, consider the following stream:
     * <pre>{@code
     *     LongStream s = LongStreams.of(1, 2, 3, 4);
     *     long count = s.peek(System.out::println).count();
     * }</pre>
     * The number of elements covered by the stream source is known and the
     * intermediate operation, {@code peek}, does not inject into or remove
     * elements from the stream (as may be the case for {@code flatMap} or
     * {@code filter} operations).  Thus the count is 4 and there is no need to
     * execute the pipeline and, as a side-effect, print out the elements.
     *
     * @return the count of elements in this stream
     */
    long count();

    /**
     * Returns an {@code OptionalDouble} describing the arithmetic mean of elements of
     * this stream, or an empty optional if this stream is empty.  This is a
     * special case of a
     * <a href="package-summary.html#Reduction">reduction</a>.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return an {@code OptionalDouble} containing the average element of this
     * stream, or an empty optional if the stream is empty
     */
    OptionalDouble average();

    /**
     * Returns a {@code LongSummaryStatistics} describing various summary data
     * about the elements of this stream.  This is a special case of a
     * <a href="package-summary.html#Reduction">reduction</a>.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">terminal
     * operation</a>.
     *
     * @return a {@code LongSummaryStatistics} describing various summary data
     * about the elements of this stream
     */
    LongSummaryStatistics summaryStatistics();

    /**
     * Returns whether any elements of this stream match the provided
     * predicate.  May not evaluate the predicate on all elements if not
     * necessary for determining the result.  If the stream is empty then
     * {@code false} is returned and the predicate is not evaluated.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * terminal operation</a>.
     *
     * <p><b>API Note:</b><br>
     * This method evaluates the <em>existential quantification</em> of the
     * predicate over the elements of the stream (for some x P(x)).
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to elements of this stream
     * @return {@code true} if any elements of the stream match the provided
     * predicate, otherwise {@code false}
     */
    boolean anyMatch(LongPredicate predicate);

    /**
     * Returns whether all elements of this stream match the provided predicate.
     * May not evaluate the predicate on all elements if not necessary for
     * determining the result.  If the stream is empty then {@code true} is
     * returned and the predicate is not evaluated.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * terminal operation</a>.
     *
     * <p><b>API Note:</b><br>
     * This method evaluates the <em>universal quantification</em> of the
     * predicate over the elements of the stream (for all x P(x)).  If the
     * stream is empty, the quantification is said to be <em>vacuously
     * satisfied</em> and is always {@code true} (regardless of P(x)).
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to elements of this stream
     * @return {@code true} if either all elements of the stream match the
     * provided predicate or the stream is empty, otherwise {@code false}
     */
    boolean allMatch(LongPredicate predicate);

    /**
     * Returns whether no elements of this stream match the provided predicate.
     * May not evaluate the predicate on all elements if not necessary for
     * determining the result.  If the stream is empty then {@code true} is
     * returned and the predicate is not evaluated.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * terminal operation</a>.
     *
     * <p><b>API Note:</b><br>
     * This method evaluates the <em>universal quantification</em> of the
     * negated predicate over the elements of the stream (for all x ~P(x)).  If
     * the stream is empty, the quantification is said to be vacuously satisfied
     * and is always {@code true}, regardless of P(x).
     *
     * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>,
     *                  <a href="package-summary.html#Statelessness">stateless</a>
     *                  predicate to apply to elements of this stream
     * @return {@code true} if either no elements of the stream match the
     * provided predicate or the stream is empty, otherwise {@code false}
     */
    boolean noneMatch(LongPredicate predicate);

    /**
     * Returns an {@link OptionalLong} describing the first element of this
     * stream, or an empty {@code OptionalLong} if the stream is empty.  If the
     * stream has no encounter order, then any element may be returned.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * terminal operation</a>.
     *
     * @return an {@code OptionalLong} describing the first element of this
     * stream, or an empty {@code OptionalLong} if the stream is empty
     */
    OptionalLong findFirst();

    /**
     * Returns an {@link OptionalLong} describing some element of the stream, or
     * an empty {@code OptionalLong} if the stream is empty.
     *
     * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting
     * terminal operation</a>.
     *
     * <p>The behavior of this operation is explicitly nondeterministic; it is
     * free to select any element in the stream.  This is to allow for maximal
     * performance in parallel operations; the cost is that multiple invocations
     * on the same source may not return the same result.  (If a stable result
     * is desired, use {@link #findFirst()} instead.)
     *
     * @return an {@code OptionalLong} describing some element of this stream,
     * or an empty {@code OptionalLong} if the stream is empty
     * @see #findFirst()
     */
    OptionalLong findAny();

    /**
     * Returns a {@code DoubleStream} consisting of the elements of this stream,
     * converted to {@code double}.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @return a {@code DoubleStream} consisting of the elements of this stream,
     * converted to {@code double}
     */
    DoubleStream asDoubleStream();

    /**
     * Returns a {@code Stream} consisting of the elements of this stream,
     * each boxed to a {@code Long}.
     *
     * <p>This is an <a href="package-summary.html#StreamOps">intermediate
     * operation</a>.
     *
     * @return a {@code Stream} consistent of the elements of this stream,
     * each boxed to {@code Long}
     */
    Stream<Long> boxed();

    @Override
    LongStream sequential();

    @Override
    LongStream parallel();

    @Override
    PrimitiveIterator.OfLong iterator();

    @Override
    Spliterator.OfLong spliterator();


    /**
     * A mutable builder for a {@code LongStream}.
     *
     * <p>A stream builder has a lifecycle, which starts in a building
     * phase, during which elements can be added, and then transitions to a built
     * phase, after which elements may not be added.  The built phase begins
     * begins when the {@link #build()} method is called, which creates an
     * ordered stream whose elements are the elements that were added to the
     * stream builder, in the order they were added.
     *
     * @see LongStreams#builder()
     * @since 1.8
     */
    public interface Builder extends LongConsumer {

        /**
         * Adds an element to the stream being built.
         *
         * @throws IllegalStateException if the builder has already transitioned
         * to the built state
         */
        @Override
        void accept(long t);

        /**
         * Adds an element to the stream being built.
         *
         * <p><b>Implementation Requirements:</b><br>
         * The default implementation behaves as if:
         * <pre>{@code
         *     accept(t)
         *     return this;
         * }</pre>
         *
         * @param t the element to add
         * @return {@code this} builder
         * @throws IllegalStateException if the builder has already transitioned
         * to the built state
         */
        Builder add(long t);

        /**
         * Builds the stream, transitioning this builder to the built state.
         * An {@code IllegalStateException} is thrown if there are further
         * attempts to operate on the builder after it has entered the built
         * state.
         *
         * @return the built stream
         * @throws IllegalStateException if the builder has already transitioned
         * to the built state
         */
        LongStream build();
    }
}
