libjava/java/util/Iterator.java

   1 /* Iterator.java -- Interface for iterating over collections
   2    Copyright (C) 1998, 2001, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package java.util;
  40
  41 /**
  42  * An object which iterates over a collection. An Iterator is used to return
  43  * the items once only, in sequence, by successive calls to the next method.
  44  * It is also possible to remove elements from the underlying collection by
  45  * using the optional remove method. Iterator is intended as a replacement
  46  * for the Enumeration interface of previous versions of Java, which did not
  47  * have the remove method and had less conveniently named methods.
  48  *
  49  * @author Original author unknown
  50  * @author Eric Blake (ebb9@email.byu.edu)
  51  * @see Collection
  52  * @see ListIterator
  53  * @see Enumeration
  54  * @since 1.2
  55  * @status updated to 1.4
  56  */
  57 public interface Iterator
  58 {
  59   /**
  60    * Tests whether there are elements remaining in the collection. In other
  61    * words, calling <code>next()</code> will not throw an exception.
  62    *
  63    * @return true if there is at least one more element in the collection
  64    */
  65   boolean hasNext();
  66
  67   /**
  68    * Obtain the next element in the collection.
  69    *
  70    * @return the next element in the collection
  71    * @throws NoSuchElementException if there are no more elements
  72    */
  73   Object next();
  74
  75   /**
  76    * Remove from the underlying collection the last element returned by next
  77    * (optional operation). This method can be called only once after each
  78    * call to <code>next()</code>. It does not affect what will be returned
  79    * by subsequent calls to next.
  80    *
  81    * @throws IllegalStateException if next has not yet been called or remove
  82    *         has already been called since the last call to next.
  83    * @throws UnsupportedOperationException if this Iterator does not support
  84    *         the remove operation.
  85    */
  86   void remove();
  87 }