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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(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 OfInt#nextInt()} and
   * {@link OfInt#forEachRemaining(IntConsumer)}
   * should be used in preference to {@link OfInt#next()} and
   * {@link OfInt#forEachRemaining(Consumer)}.
   *
   * <p>Iteration of primitive values using boxing-based methods
   * {@link Iterator#next next()} and
   * {@link Iterator#forEachRemaining(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 Consumer} for
   *        {@code T}, such as {@link 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);
              }
          }
      }
  }
  