Java example source code file (PrimitiveIterator.java)

This example Java source code file (PrimitiveIterator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

double, doubleconsumer, intconsumer, integer, longconsumer, ofdouble, ofint, oflong, override, primitiveiterator, suppresswarnings, t_cons

The PrimitiveIterator.java Java example source code

/*
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
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 type of elements returned by this PrimitiveIterator.  The
 *        type must be a wrapper type for a primitive type, such as
 *        {@code Integer} for the primitive {@code int} type.
 * @param <T_CONS> the type of primitive consumer.  The type must be a
 *        primitive specialization of {@link java.util.function.Consumer} for
 *        {@code T}, such as {@link java.util.function.IntConsumer} for
 *        {@code Integer}.
 *
 * @since 1.8
 */
public interface PrimitiveIterator<T, T_CONS> extends Iterator {

    /**
     * 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.
     *
     * @param action The action to be performed for each element
     * @throws NullPointerException if the specified action is null
     */
    @SuppressWarnings("overloads")
    void forEachRemaining(T_CONS action);

    /**
     * An Iterator specialized for {@code int} values.
     * @since 1.8
     */
    public static interface OfInt extends PrimitiveIterator<Integer, IntConsumer> {

        /**
         * 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 until all elements
         * have been processed or the action throws an exception.  Actions are
         * performed in the order of iteration, if that order is specified.
         * 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, LongConsumer> {

        /**
         * 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 until all elements
         * have been processed or the action throws an exception.  Actions are
         * performed in the order of iteration, if that order is specified.
         * 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, DoubleConsumer> {

        /**
         * 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 until all elements
         * have been processed or the action throws an exception.  Actions are
         * performed in the order of iteration, if that order is specified.
         * 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);
            }
        }
    }
}