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 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

 * 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,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.util;

import java.util.function.Consumer;

import java.util.function.DoubleConsumer;

import java.util.function.IntConsumer;

import java.util.function.LongConsumer;

/**

 * A base type for primitive specializations of {@code Iterator}.  Specialized

 * subtypes are provided for {@link OfInt int}, {@link OfLong long}, and

 * {@link OfDouble double} values.

 *

 * <p>The specialized subtype default implementations of {@link Iterator#next}

 * and {@link Iterator#forEachRemaining(java.util.function.Consumer)} box

 * primitive values to instances of their corresponding wrapper class.  Such

 * boxing may offset any advantages gained when using the primitive

 * specializations.  To avoid boxing, the corresponding primitive-based methods

 * should be used.  For example, {@link PrimitiveIterator.OfInt#nextInt()} and

 * {@link PrimitiveIterator.OfInt#forEachRemaining(java.util.function.IntConsumer)}

 * should be used in preference to {@link PrimitiveIterator.OfInt#next()} and

 * {@link PrimitiveIterator.OfInt#forEachRemaining(java.util.function.Consumer)}.

 *

 * <p>Iteration of primitive values using boxing-based methods

 * {@link Iterator#next next()} and

 * {@link Iterator#forEachRemaining(java.util.function.Consumer) forEachRemaining()},

 * does not affect the order in which the values, transformed to boxed values,

 * are encountered.

 *

 * @implNote

 * If the boolean system property {@code org.openjdk.java.util.stream.tripwire}

 * is set to {@code true} then diagnostic warnings are reported if boxing of

 * primitive values occur when operating on primitive subtype specializations.

 *

 * @param <T> the boxed type of the primitive type

 * @since 1.8

 */

public interface PrimitiveIterator<T> extends Iterator<T> {

    /**

     * An Iterator specialized for {@code int} values.

     * @since 1.8

     */

    public static interface OfInt extends PrimitiveIterator<Integer> {

        /**

         * Returns the next {@code int} element in the iteration.

         *

         * @return the next {@code int} element in the iteration

         * @throws NoSuchElementException if the iteration has no more elements

         */

        int nextInt();

        /**

         * Performs the given action for each remaining element, in the order

         * elements occur when iterating, until all elements have been processed

         * or the action throws an exception.  Errors or runtime exceptions

         * thrown by the action are relayed to the caller.

         *

         * @implSpec

         * <p>The default implementation behaves as if:

         * <pre>{@code

         *     while (hasNext())

         *         action.accept(nextInt());

         * }</pre>

         *

         * @param action The action to be performed for each element

         * @throws NullPointerException if the specified action is null

         */

        default void forEachRemaining(IntConsumer action) {

            Objects.requireNonNull(action);

            while (hasNext())

                action.accept(nextInt());

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * The default implementation boxes the result of calling

         * {@link #nextInt()}, and returns that boxed result.

         */

        @Override

        default Integer next() {

            if (Tripwire.ENABLED)

                Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfInt.nextInt()");

            return nextInt();

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * If the action is an instance of {@code IntConsumer} then it is cast

         * to {@code IntConsumer} and passed to {@link #forEachRemaining};

         * otherwise the action is adapted to an instance of

         * {@code IntConsumer}, by boxing the argument of {@code IntConsumer},

         * and then passed to {@link #forEachRemaining}.

         */

        @Override

        default void forEachRemaining(Consumer<? super Integer> action) {

            if (action instanceof IntConsumer) {

                forEachRemaining((IntConsumer) action);

            }

            else {

                // The method reference action::accept is never null

                Objects.requireNonNull(action);

                if (Tripwire.ENABLED)

                    Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfInt.forEachRemainingInt(action::accept)");

                forEachRemaining((IntConsumer) action::accept);

            }

        }

    }

    /**

     * An Iterator specialized for {@code long} values.

     * @since 1.8

     */

    public static interface OfLong extends PrimitiveIterator<Long> {

        /**

         * Returns the next {@code long} element in the iteration.

         *

         * @return the next {@code long} element in the iteration

         * @throws NoSuchElementException if the iteration has no more elements

         */

        long nextLong();

        /**

         * Performs the given action for each remaining element, in the order

         * elements occur when iterating, until all elements have been processed

         * or the action throws an exception.  Errors or runtime exceptions

         * thrown by the action are relayed to the caller.

         *

         * @implSpec

         * <p>The default implementation behaves as if:

         * <pre>{@code

         *     while (hasNext())

         *         action.accept(nextLong());

         * }</pre>

         *

         * @param action The action to be performed for each element

         * @throws NullPointerException if the specified action is null

         */

        default void forEachRemaining(LongConsumer action) {

            Objects.requireNonNull(action);

            while (hasNext())

                action.accept(nextLong());

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * The default implementation boxes the result of calling

         * {@link #nextLong()}, and returns that boxed result.

         */

        @Override

        default Long next() {

            if (Tripwire.ENABLED)

                Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfLong.nextLong()");

            return nextLong();

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * If the action is an instance of {@code LongConsumer} then it is cast

         * to {@code LongConsumer} and passed to {@link #forEachRemaining};

         * otherwise the action is adapted to an instance of

         * {@code LongConsumer}, by boxing the argument of {@code LongConsumer},

         * and then passed to {@link #forEachRemaining}.

         */

        @Override

        default void forEachRemaining(Consumer<? super Long> action) {

            if (action instanceof LongConsumer) {

                forEachRemaining((LongConsumer) action);

            }

            else {

                // The method reference action::accept is never null

                Objects.requireNonNull(action);

                if (Tripwire.ENABLED)

                    Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfLong.forEachRemainingLong(action::accept)");

                forEachRemaining((LongConsumer) action::accept);

            }

        }

    }

    /**

     * An Iterator specialized for {@code double} values.

     * @since 1.8

     */

    public static interface OfDouble extends PrimitiveIterator<Double> {

        /**

         * Returns the next {@code double} element in the iteration.

         *

         * @return the next {@code double} element in the iteration

         * @throws NoSuchElementException if the iteration has no more elements

         */

        double nextDouble();

        /**

         * Performs the given action for each remaining element, in the order

         * elements occur when iterating, until all elements have been processed

         * or the action throws an exception.  Errors or runtime exceptions

         * thrown by the action are relayed to the caller.

         *

         * @implSpec

         * <p>The default implementation behaves as if:

         * <pre>{@code

         *     while (hasNext())

         *         action.accept(nextDouble());

         * }</pre>

         *

         * @param action The action to be performed for each element

         * @throws NullPointerException if the specified action is null

         */

        default void forEachRemaining(DoubleConsumer action) {

            Objects.requireNonNull(action);

            while (hasNext())

                action.accept(nextDouble());

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * The default implementation boxes the result of calling

         * {@link #nextDouble()}, and returns that boxed result.

         */

        @Override

        default Double next() {

            if (Tripwire.ENABLED)

                Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfDouble.nextLong()");

            return nextDouble();

        }

        /**

         * {@inheritDoc}

         * @implSpec

         * If the action is an instance of {@code DoubleConsumer} then it is

         * cast to {@code DoubleConsumer} and passed to

         * {@link #forEachRemaining}; otherwise the action is adapted to

         * an instance of {@code DoubleConsumer}, by boxing the argument of

         * {@code DoubleConsumer}, and then passed to

         * {@link #forEachRemaining}.

         */

        @Override

        default void forEachRemaining(Consumer<? super Double> action) {

            if (action instanceof DoubleConsumer) {

                forEachRemaining((DoubleConsumer) action);

            }

            else {

                // The method reference action::accept is never null

                Objects.requireNonNull(action);

                if (Tripwire.ENABLED)

                    Tripwire.trip(getClass(), "{0} calling PrimitiveIterator.OfDouble.forEachRemainingDouble(action::accept)");

                forEachRemaining((DoubleConsumer) action::accept);

            }

        }

    }

}