1 /* 2 * Copyright 1997-2006 Sun Microsystems, Inc. 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. Sun designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 22 * CA 95054 USA or visit www.sun.com if you need additional information or 23 * have any questions. 24 */ 25 26 package java.util; 27 28 /** 29 * An iterator over a collection. {@code Iterator} takes the place of 30 * {@link Enumeration} in the Java Collections Framework. Iterators 31 * differ from enumerations in two ways: 32 * 33 * <ul> 34 * <li> Iterators allow the caller to remove elements from the 35 * underlying collection during the iteration with well-defined 36 * semantics. 37 * <li> Method names have been improved. 38 * </ul> 39 * 40 * <p>This interface is a member of the 41 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 42 * Java Collections Framework</a>. 43 * 44 * @author Josh Bloch 45 * @see Collection 46 * @see ListIterator 47 * @see Iterable 48 * @since 1.2 49 */ 50 public interface Iterator<E> { 51 /** 52 * Returns {@code true} if the iteration has more elements. 53 * (In other words, returns {@code true} if {@link #next} would 54 * return an element rather than throwing an exception.) 55 * 56 * @return {@code true} if the iteration has more elements 57 */ 58 boolean hasNext(); 59 60 /** 61 * Returns the next element in the iteration. 62 * 63 * @return the next element in the iteration 64 * @throws NoSuchElementException if the iteration has no more elements 65 */ 66 E next(); 67 68 /** 69 * Removes from the underlying collection the last element returned 70 * by this iterator (optional operation). This method can be called 71 * only once per call to {@link #next}. The behavior of an iterator 72 * is unspecified if the underlying collection is modified while the 73 * iteration is in progress in any way other than by calling this 74 * method. 75 * 76 * @throws UnsupportedOperationException if the {@code remove} 77 * operation is not supported by this iterator 78 * 79 * @throws IllegalStateException if the {@code next} method has not 80 * yet been called, or the {@code remove} method has already 81 * been called after the last call to the {@code next} 82 * method 83 */ 84 void remove(); 85 }