001 /* Iterator.java -- Interface for iterating over collections 002 Copyright (C) 1998, 2001, 2004, 2005 Free Software Foundation, Inc. 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 039 package java.util; 040 041 /** 042 * An object which iterates over a collection. An Iterator is used to return 043 * the items once only, in sequence, by successive calls to the next method. 044 * It is also possible to remove elements from the underlying collection by 045 * using the optional remove method. Iterator is intended as a replacement 046 * for the Enumeration interface of previous versions of Java, which did not 047 * have the remove method and had less conveniently named methods. 048 * 049 * @author Original author unknown 050 * @author Eric Blake (ebb9@email.byu.edu) 051 * @see Collection 052 * @see ListIterator 053 * @see Enumeration 054 * @since 1.2 055 * @status updated to 1.4 056 */ 057 public interface Iterator<E> 058 { 059 /** 060 * Tests whether there are elements remaining in the collection. In other 061 * words, calling <code>next()</code> will not throw an exception. 062 * 063 * @return true if there is at least one more element in the collection 064 */ 065 boolean hasNext(); 066 067 /** 068 * Obtain the next element in the collection. 069 * 070 * @return the next element in the collection 071 * @throws NoSuchElementException if there are no more elements 072 */ 073 E next(); 074 075 /** 076 * Remove from the underlying collection the last element returned by next 077 * (optional operation). This method can be called only once after each 078 * call to <code>next()</code>. It does not affect what will be returned 079 * by subsequent calls to next. 080 * 081 * @throws IllegalStateException if next has not yet been called or remove 082 * has already been called since the last call to next. 083 * @throws UnsupportedOperationException if this Iterator does not support 084 * the remove operation. 085 */ 086 void remove(); 087 }