01: /*
02: * @(#)Iterator.java 1.21 06/10/10
03: *
04: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
05: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
06: *
07: * This program is free software; you can redistribute it and/or
08: * modify it under the terms of the GNU General Public License version
09: * 2 only, as published by the Free Software Foundation.
10: *
11: * This program 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 version 2 for more details (a copy is
15: * included at /legal/license.txt).
16: *
17: * You should have received a copy of the GNU General Public License
18: * version 2 along with this work; if not, write to the Free Software
19: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20: * 02110-1301 USA
21: *
22: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
23: * Clara, CA 95054 or visit www.sun.com if you need additional
24: * information or have any questions.
25: *
26: */
27:
28: package java.util;
29:
30: /**
31: * An iterator over a collection. Iterator takes the place of Enumeration in
32: * the Java collections framework. Iterators differ from enumerations in two
33: * ways: <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><p>
39: *
40: * This interface is a member of the
41: * <a href="{@docRoot}/../guide/collections/index.html">
42: * Java Collections Framework</a>.
43: *
44: * @author Josh Bloch
45: * @version 1.14, 02/02/00
46: * @see Collection
47: * @see ListIterator
48: * @see Enumeration
49: * @since 1.2
50: */
51: public interface Iterator {
52: /**
53: * Returns <tt>true</tt> if the iteration has more elements. (In other
54: * words, returns <tt>true</tt> if <tt>next</tt> would return an element
55: * rather than throwing an exception.)
56: *
57: * @return <tt>true</tt> if the iterator has more elements.
58: */
59: boolean hasNext();
60:
61: /**
62: * Returns the next element in the iteration.
63: *
64: * @return the next element in the iteration.
65: * @exception NoSuchElementException iteration has no more elements.
66: */
67: Object next();
68:
69: /**
70: *
71: * Removes from the underlying collection the last element returned by the
72: * iterator (optional operation). This method can be called only once per
73: * call to <tt>next</tt>. The behavior of an iterator is unspecified if
74: * the underlying collection is modified while the iteration is in
75: * progress in any way other than by calling this method.
76: *
77: * @exception UnsupportedOperationException if the <tt>remove</tt>
78: * operation is not supported by this Iterator.
79:
80: * @exception IllegalStateException if the <tt>next</tt> method has not
81: * yet been called, or the <tt>remove</tt> method has already
82: * been called after the last call to the <tt>next</tt>
83: * method.
84: */
85: void remove();
86: }
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