/*
 * Copyright (c) 2019, 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.lang;

import java.util.Iterator;

/**
 * An Iterable from which only a single Iterator can be obtained.
 *
 * @apiNote
 * IterableOnce is functionally identical to Iterable. A class can
 * implement IterableOnce in preference to Iterable in order to signal
 * to applications that only a single Iterator can be obtained. It is
 * recommended that attempts to call the iterator() method the second
 * and subsequent time results in IllegalStateException.
 *
 * @param <T> the type of elements returned by the iterator
 */
public interface IterableOnce<T> extends Iterable<T> {
    /**
     * Returns an iterator over elements of type {@code T}. This method
     * can be called successfully only once. The second and subsequent
     * invocations of this method throw IllegalStateException.
     *
     * @return an Iterator
     * @throws IllegalStateException if this method has been called previously
     */
    Iterator<T> iterator();
}