Java tutorial
/* * 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<T> { /** * 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); } } } }