Source for java.util.Iterator

   1: /* Iterator.java -- Interface for iterating over collections
   2:    Copyright (C) 1998, 2001, 2004, 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., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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<E>
  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:   E 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: }