/*

 * Copyright (c) 2003, 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.lang;

import java.util.Iterator;

import java.util.Objects;

import java.util.Spliterator;

import java.util.Spliterators;

import java.util.function.Consumer;

/**

 * Implementing this interface allows an object to be the target of

 * the "for-each loop" statement. See

 * <strong>

 * <a href="{@docRoot}/../technotes/guides/language/foreach.html">For-each Loop</a>

 * </strong>

 *

 * @param <T> the type of elements returned by the iterator

 *

 * @since 1.5

 * @jls 14.14.2 The enhanced for statement

 */

public interface Iterable<T> {

    /**

     * Returns an iterator over elements of type {@code T}.

     *

     * @return an Iterator.

     */

    Iterator<T> iterator();

    /**

     * Performs the given action for each element of the {@code Iterable}

     * until all elements have been processed or the action throws an

     * exception.  Unless otherwise specified by the implementing class,

     * actions are performed in the order of iteration (if an iteration order

     * is specified).  Exceptions thrown by the action are relayed to the

     * caller.

     *

     * @implSpec

     * <p>The default implementation behaves as if:

     * <pre>{@code

     *     for (T t : this)

     *         action.accept(t);

     * }</pre>

     *

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

     * @throws NullPointerException if the specified action is null

     * @since 1.8

     */

    default void forEach(Consumer<? super T> action) {

        Objects.requireNonNull(action);

        for (T t : this) {

            action.accept(t);

        }

    }

    /**

     * Creates a {@link Spliterator} over the elements described by this

     * {@code Iterable}.

     *

     * @implSpec

     * The default implementation creates an

     * <em><a href="Spliterator.html#binding">early-binding</a></em>

     * spliterator from the iterable's {@code Iterator}.  The spliterator

     * inherits the <em>fail-fast</em> properties of the iterable's iterator.

     *

     * @implNote

     * The default implementation should usually be overridden.  The

     * spliterator returned by the default implementation has poor splitting

     * capabilities, is unsized, and does not report any spliterator

     * characteristics. Implementing classes can nearly always provide a

     * better implementation.

     *

     * @return a {@code Spliterator} over the elements described by this

     * {@code Iterable}.

     * @since 1.8

     */

    default Spliterator<T> spliterator() {

        return Spliterators.spliteratorUnknownSize(iterator(), 0);

    }

}