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package java.util.stream;

import java.util.Arrays;
import java.util.IntSummaryStatistics;
import java.util.Objects;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.PrimitiveIterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.IntPredicate;
import java.util.function.IntSupplier;
import java.util.function.IntToDoubleFunction;
import java.util.function.IntToLongFunction;
import java.util.function.IntUnaryOperator;
import java.util.function.ObjIntConsumer;
import java.util.function.Supplier;

/**
 * A sequence of primitive int-valued elements supporting sequential and parallel
 * aggregate operations. This is the {@code int} primitive specialization of
 * {@link Stream}.
 *
 * <p>The following example illustrates an aggregate operation using
 * {@link Stream} and {@link IntStream}, computing the sum of the weights of the
 * red widgets:
 *
 * <pre>{@code
 * int sum = widgets.stream()
 * .filter(w -> w.getColor() == RED)
 * .mapToInt(w -> w.getWeight())
 * .sum();
 * }</pre>
 *
 * See the class documentation for {@link Stream} and the package documentation
 * for <a href="package-summary.html">java.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">java.util.stream</a>
 */
public interface IntStream extends BaseStream<Integer, IntStream> {

 /**
 * 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
 */
 IntStream filter(IntPredicate 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
 */
 IntStream map(IntUnaryOperator 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(IntFunction<? extends U> mapper);

 /**
 * Returns a {@code LongStream} 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 mapToLong(IntToLongFunction 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(IntToDoubleFunction 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 java.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 an
 * {@code IntStream} of new values
 * @return the new stream
 * @see Stream#flatMap(Function)
 */
 IntStream flatMap(IntFunction<? extends IntStream> 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
 */
 IntStream 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
 */
 IntStream 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.
 *
 * @apiNote 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
 * IntStream.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
 */
 IntStream peek(IntConsumer 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>.
 *
 * @apiNote
 * 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 #generate(IntSupplier)}) 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
 */
 IntStream 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>.
 *
 * @apiNote
 * 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 #generate(IntSupplier)}) 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
 */
 IntStream 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>.
 *
 * @implSpec
 * 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.
 *
 * @apiNote
 * 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 #generate(IntSupplier)})
 * 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
 */
 default IntStream takeWhile(IntPredicate predicate) {
 Objects.requireNonNull(predicate);
 // Reuses the unordered spliterator, which, when encounter is present,
 // is safe to use as long as it configured not to split
 return StreamSupport.intStream(
 new WhileOps.UnorderedWhileSpliterator.OfInt.Taking(spliterator(), true, predicate),
 isParallel()).onClose(this::close);
 }

 /**
 * 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>.
 *
 * @implSpec
 * 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.
 *
 * @apiNote
 * 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 #generate(IntSupplier)})
 * 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
 */
 default IntStream dropWhile(IntPredicate predicate) {
 Objects.requireNonNull(predicate);
 // Reuses the unordered spliterator, which, when encounter is present,
 // is safe to use as long as it configured not to split
 return StreamSupport.intStream(
 new WhileOps.UnorderedWhileSpliterator.OfInt.Dropping(spliterator(), true, predicate),
 isParallel()).onClose(this::close);
 }

 /**
 * 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(IntConsumer 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(IntConsumer)
 */
 void forEachOrdered(IntConsumer 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
 */
 int[] 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
 * int result = identity;
 * for (int element : this stream)
 * result = accumulator.applyAsInt(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>.
 *
 * @apiNote Sum, min, max, and average are all special cases of reduction.
 * Summing a stream of numbers can be expressed as:
 *
 * <pre>{@code
 * int sum = integers.reduce(0, (a, b) -> a+b);
 * }</pre>
 *
 * or more compactly:
 *
 * <pre>{@code
 * int sum = integers.reduce(0, Integer::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()
 */
 int reduce(int identity, IntBinaryOperator 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 OptionalInt} describing the reduced value,
 * if any. This is equivalent to:
 * <pre>{@code
 * boolean foundAny = false;
 * int result = null;
 * for (int element : this stream) {
 * if (!foundAny) {
 * foundAny = true;
 * result = element;
 * }
 * else
 * result = accumulator.applyAsInt(result, element);
 * }
 * return foundAny ? OptionalInt.of(result) : OptionalInt.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(int, IntBinaryOperator)
 */
 OptionalInt reduce(IntBinaryOperator 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 (int element : this stream)
 * accumulator.accept(result, element);
 * return result;
 * }</pre>
 *
 * <p>Like {@link #reduce(int, IntBinaryOperator)}, {@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,
 ObjIntConsumer<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, Integer::sum);
 * }</pre>
 *
 * <p>This is a <a href="package-summary.html#StreamOps">terminal
 * operation</a>.
 *
 * @return the sum of elements in this stream
 */
 int sum();

 /**
 * Returns an {@code OptionalInt} 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(Integer::min);
 * }</pre>
 *
 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>.
 *
 * @return an {@code OptionalInt} containing the minimum element of this
 * stream, or an empty {@code OptionalInt} if the stream is empty
 */
 OptionalInt min();

 /**
 * Returns an {@code OptionalInt} 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(Integer::max);
 * }</pre>
 *
 * <p>This is a <a href="package-summary.html#StreamOps">terminal
 * operation</a>.
 *
 * @return an {@code OptionalInt} containing the maximum element of this
 * stream, or an empty {@code OptionalInt} if the stream is empty
 */
 OptionalInt 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
 * equivalent to:
 * <pre>{@code
 * return mapToLong(e -> 1L).sum();
 * }</pre>
 *
 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>.
 *
 * @apiNote
 * 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
 * IntStream s = IntStream.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 an {@code IntSummaryStatistics} 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 an {@code IntSummaryStatistics} describing various summary data
 * about the elements of this stream
 */
 IntSummaryStatistics 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>.
 *
 * @apiNote
 * 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(IntPredicate 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>.
 *
 * @apiNote
 * 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(IntPredicate 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>.
 *
 * @apiNote
 * 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(IntPredicate predicate);

 /**
 * Returns an {@link OptionalInt} describing the first element of this
 * stream, or an empty {@code OptionalInt} 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 OptionalInt} describing the first element of this stream,
 * or an empty {@code OptionalInt} if the stream is empty
 */
 OptionalInt findFirst();

 /**
 * Returns an {@link OptionalInt} describing some element of the stream, or
 * an empty {@code OptionalInt} 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 OptionalInt} describing some element of this stream, or
 * an empty {@code OptionalInt} if the stream is empty
 * @see #findFirst()
 */
 OptionalInt findAny();

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

 /**
 * 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 an {@code Integer}.
 *
 * <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 an {@code Integer}
 */
 Stream<Integer> boxed();

 @Override
 IntStream sequential();

 @Override
 IntStream parallel();

 @Override
 PrimitiveIterator.OfInt iterator();

 @Override
 Spliterator.OfInt spliterator();

 // Static factories

 /**
 * Returns a builder for an {@code IntStream}.
 *
 * @return a stream builder
 */
 public static Builder builder() {
 return new Streams.IntStreamBuilderImpl();
 }

 /**
 * Returns an empty sequential {@code IntStream}.
 *
 * @return an empty sequential stream
 */
 public static IntStream empty() {
 return StreamSupport.intStream(Spliterators.emptyIntSpliterator(), false);
 }

 /**
 * Returns a sequential {@code IntStream} containing a single element.
 *
 * @param t the single element
 * @return a singleton sequential stream
 */
 public static IntStream of(int t) {
 return StreamSupport.intStream(new Streams.IntStreamBuilderImpl(t), false);
 }

 /**
 * Returns a sequential ordered stream whose elements are the specified values.
 *
 * @param values the elements of the new stream
 * @return the new stream
 */
 public static IntStream of(int... values) {
 return Arrays.stream(values);
 }

 /**
 * Returns an infinite sequential ordered {@code IntStream} produced by iterative
 * application of a function {@code f} to an initial element {@code seed},
 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
 * {@code f(f(seed))}, etc.
 *
 * <p>The first element (position {@code 0}) in the {@code IntStream} will be
 * the provided {@code seed}. For {@code n > 0}, the element at position
 * {@code n}, will be the result of applying the function {@code f} to the
 * element at position {@code n - 1}.
 *
 * <p>The action of applying {@code f} for one element
 * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
 * the action of applying {@code f} for subsequent elements. For any given
 * element the action may be performed in whatever thread the library
 * chooses.
 *
 * @param seed the initial element
 * @param f a function to be applied to the previous element to produce
 * a new element
 * @return a new sequential {@code IntStream}
 */
 public static IntStream iterate(final int seed, final IntUnaryOperator f) {
 Objects.requireNonNull(f);
 Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE,
 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
 int prev;
 boolean started;

 @Override
 public boolean tryAdvance(IntConsumer action) {
 Objects.requireNonNull(action);
 int t;
 if (started)
 t = f.applyAsInt(prev);
 else {
 t = seed;
 started = true;
 }
 action.accept(prev = t);
 return true;
 }
 };
 return StreamSupport.intStream(spliterator, false);
 }

 /**
 * Returns a sequential ordered {@code IntStream} produced by iterative
 * application of the given {@code next} function to an initial element,
 * conditioned on satisfying the given {@code hasNext} predicate. The
 * stream terminates as soon as the {@code hasNext} predicate returns false.
 *
 * <p>{@code IntStream.iterate} should produce the same sequence of elements as
 * produced by the corresponding for-loop:
 * <pre>{@code
 * for (int index=seed; hasNext.test(index); index = next.applyAsInt(index)) {
 * ...
 * }
 * }</pre>
 *
 * <p>The resulting sequence may be empty if the {@code hasNext} predicate
 * does not hold on the seed value. Otherwise the first element will be the
 * supplied {@code seed} value, the next element (if present) will be the
 * result of applying the {@code next} function to the {@code seed} value,
 * and so on iteratively until the {@code hasNext} predicate indicates that
 * the stream should terminate.
 *
 * <p>The action of applying the {@code hasNext} predicate to an element
 * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a>
 * the action of applying the {@code next} function to that element. The
 * action of applying the {@code next} function for one element
 * <i>happens-before</i> the action of applying the {@code hasNext}
 * predicate for subsequent elements. For any given element an action may
 * be performed in whatever thread the library chooses.
 *
 * @param seed the initial element
 * @param hasNext a predicate to apply to elements to determine when the
 * stream must terminate.
 * @param next a function to be applied to the previous element to produce
 * a new element
 * @return a new sequential {@code IntStream}
 * @since 9
 */
 public static IntStream iterate(int seed, IntPredicate hasNext, IntUnaryOperator next) {
 Objects.requireNonNull(next);
 Objects.requireNonNull(hasNext);
 Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE,
 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) {
 int prev;
 boolean started, finished;

 @Override
 public boolean tryAdvance(IntConsumer action) {
 Objects.requireNonNull(action);
 if (finished)
 return false;
 int t;
 if (started)
 t = next.applyAsInt(prev);
 else {
 t = seed;
 started = true;
 }
 if (!hasNext.test(t)) {
 finished = true;
 return false;
 }
 action.accept(prev = t);
 return true;
 }

 @Override
 public void forEachRemaining(IntConsumer action) {
 Objects.requireNonNull(action);
 if (finished)
 return;
 finished = true;
 int t = started ? next.applyAsInt(prev) : seed;
 while (hasNext.test(t)) {
 action.accept(t);
 t = next.applyAsInt(t);
 }
 }
 };
 return StreamSupport.intStream(spliterator, false);
 }

 /**
 * Returns an infinite sequential unordered stream where each element is
 * generated by the provided {@code IntSupplier}. This is suitable for
 * generating constant streams, streams of random elements, etc.
 *
 * @param s the {@code IntSupplier} for generated elements
 * @return a new infinite sequential unordered {@code IntStream}
 */
 public static IntStream generate(IntSupplier s) {
 Objects.requireNonNull(s);
 return StreamSupport.intStream(
 new StreamSpliterators.InfiniteSupplyingSpliterator.OfInt(Long.MAX_VALUE, s), false);
 }

 /**
 * Returns a sequential ordered {@code IntStream} from {@code startInclusive}
 * (inclusive) to {@code endExclusive} (exclusive) by an incremental step of
 * {@code 1}.
 *
 * @apiNote
 * <p>An equivalent sequence of increasing values can be produced
 * sequentially using a {@code for} loop as follows:
 * <pre>{@code
 * for (int i = startInclusive; i < endExclusive ; i++) { ... }
 * }</pre>
 *
 * @param startInclusive the (inclusive) initial value
 * @param endExclusive the exclusive upper bound
 * @return a sequential {@code IntStream} for the range of {@code int}
 * elements
 */
 public static IntStream range(int startInclusive, int endExclusive) {
 if (startInclusive >= endExclusive) {
 return empty();
 } else {
 return StreamSupport.intStream(
 new Streams.RangeIntSpliterator(startInclusive, endExclusive, false), false);
 }
 }

 /**
 * Returns a sequential ordered {@code IntStream} from {@code startInclusive}
 * (inclusive) to {@code endInclusive} (inclusive) by an incremental step of
 * {@code 1}.
 *
 * @apiNote
 * <p>An equivalent sequence of increasing values can be produced
 * sequentially using a {@code for} loop as follows:
 * <pre>{@code
 * for (int i = startInclusive; i <= endInclusive ; i++) { ... }
 * }</pre>
 *
 * @param startInclusive the (inclusive) initial value
 * @param endInclusive the inclusive upper bound
 * @return a sequential {@code IntStream} for the range of {@code int}
 * elements
 */
 public static IntStream rangeClosed(int startInclusive, int endInclusive) {
 if (startInclusive > endInclusive) {
 return empty();
 } else {
 return StreamSupport.intStream(
 new Streams.RangeIntSpliterator(startInclusive, endInclusive, true), false);
 }
 }

 /**
 * Creates a lazily concatenated stream whose elements are all the
 * elements of the first stream followed by all the elements of the
 * second stream. The resulting stream is ordered if both
 * of the input streams are ordered, and parallel if either of the input
 * streams is parallel. When the resulting stream is closed, the close
 * handlers for both input streams are invoked.
 *
 * <p>This method operates on the two input streams and binds each stream
 * to its source. As a result subsequent modifications to an input stream
 * source may not be reflected in the concatenated stream result.
 *
 * @implNote
 * Use caution when constructing streams from repeated concatenation.
 * Accessing an element of a deeply concatenated stream can result in deep
 * call chains, or even {@code StackOverflowError}.
 *
 * @apiNote
 * To preserve optimization opportunities this method binds each stream to
 * its source and accepts only two streams as parameters. For example, the
 * exact size of the concatenated stream source can be computed if the exact
 * size of each input stream source is known.
 * To concatenate more streams without binding, or without nested calls to
 * this method, try creating a stream of streams and flat-mapping with the
 * identity function, for example:
 * <pre>{@code
 * IntStream concat = Stream.of(s1, s2, s3, s4).flatMapToInt(s -> s);
 * }</pre>
 *
 * @param a the first stream
 * @param b the second stream
 * @return the concatenation of the two input streams
 */
 public static IntStream concat(IntStream a, IntStream b) {
 Objects.requireNonNull(a);
 Objects.requireNonNull(b);

 Spliterator.OfInt split = new Streams.ConcatSpliterator.OfInt(
 a.spliterator(), b.spliterator());
 IntStream stream = StreamSupport.intStream(split, a.isParallel() || b.isParallel());
 return stream.onClose(Streams.composedClose(a, b));
 }

 /**
 * A mutable builder for an {@code IntStream}.
 *
 * <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 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 IntStream#builder()
 * @since 1.8
 */
 public interface Builder extends IntConsumer {

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

 /**
 * Adds an element to the stream being built.
 *
 * @implSpec
 * 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
 */
 default Builder add(int t) {
 accept(t);
 return this;
 }

 /**
 * 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
 */
 IntStream build();
 }
}