1 /* 2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package javany.util; 27 28 import java.util.Objects; 29 import javany.util.function.Consumer; 30 31 /** 32 * An iterator over a collection. {@code Iterator} takes the place of 33 * {@link Enumeration} in the Java Collections Framework. Iterators 34 * differ from enumerations in two ways: 35 * 36 * <ul> 37 * <li> Iterators allow the caller to remove elements from the 38 * underlying collection during the iteration with well-defined 39 * semantics. 40 * <li> Method names have been improved. 41 * </ul> 42 * 43 * <p>This interface is a member of the 44 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 45 * Java Collections Framework</a>. 46 * 47 * @param <E> the type of elements returned by this iterator 48 * 49 * @author Josh Bloch 50 * @see Collection 51 * @see ListIterator 52 * @see Iterable 53 * @since 1.2 54 */ 55 public interface Iterator<any E> { 56 /** 57 * Returns {@code true} if the iteration has more elements. 58 * (In other words, returns {@code true} if {@link #next} would 59 * return an element rather than throwing an exception.) 60 * 61 * @return {@code true} if the iteration has more elements 62 */ 63 boolean hasNext(); 64 65 /** 66 * Returns the next element in the iteration. 67 * 68 * @return the next element in the iteration 69 * @throws java.util.NoSuchElementException if the iteration has no more elements 70 */ 71 E next(); 72 73 /** 74 * Removes from the underlying collection the last element returned 75 * by this iterator (optional operation). This method can be called 76 * only once per call to {@link #next}. The behavior of an iterator 77 * is unspecified if the underlying collection is modified while the 78 * iteration is in progress in any way other than by calling this 79 * method. 80 * 81 * @implSpec 82 * The default implementation throws an instance of 83 * {@link UnsupportedOperationException} and performs no other action. 84 * 85 * @throws UnsupportedOperationException if the {@code remove} 86 * operation is not supported by this iterator 87 * 88 * @throws IllegalStateException if the {@code next} method has not 89 * yet been called, or the {@code remove} method has already 90 * been called after the last call to the {@code next} 91 * method 92 */ 93 default void remove() { 94 throw new UnsupportedOperationException("remove"); 95 } 96 97 /** 98 * Performs the given action for each remaining element until all elements 99 * have been processed or the action throws an exception. Actions are 100 * performed in the order of iteration, if that order is specified. 101 * Exceptions thrown by the action are relayed to the caller. 102 * 103 * @implSpec 104 * <p>The default implementation behaves as if: 105 * <pre>{@code 106 * while (hasNext()) 107 * action.accept(next()); 108 * }</pre> 109 * 110 * @param action The action to be performed for each element 111 * @throws NullPointerException if the specified action is null 112 * @since 1.8 113 */ 114 default void forEachRemaining(Consumer<? super E> action) { 115 Objects.requireNonNull(action); 116 while (hasNext()) 117 action.accept(next()); 118 } 119 }