1 /*
2 * $Source$
3 * $Revision$
4 *
5 * Copyright (C) 2000 William Chesters
6 *
7 * Part of Melati (http://melati.org), a framework for the rapid
8 * development of clean, maintainable web applications.
9 *
10 * Melati is free software; Permission is granted to copy, distribute
11 * and/or modify this software under the terms either:
12 *
13 * a) the GNU General Public License as published by the Free Software
14 * Foundation; either version 2 of the License, or (at your option)
15 * any later version,
16 *
17 * or
18 *
19 * b) any version of the Melati Software License, as published
20 * at http://melati.org
21 *
22 * You should have received a copy of the GNU General Public License and
23 * the Melati Software License along with this program;
24 * if not, write to the Free Software Foundation, Inc.,
25 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
26 * GNU General Public License and visit http://melati.org to obtain the
27 * Melati Software License.
28 *
29 * Feel free to contact the Developers of Melati (http://melati.org),
30 * if you would like to work out a different arrangement than the options
31 * outlined here. It is our intention to allow Melati to be used by as
32 * wide an audience as possible.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * Contact details for copyright holder:
40 *
41 * William Chesters <williamc At paneris.org>
42 * http://paneris.org/~williamc
43 * Obrechtstraat 114, 2517VX Den Haag, The Netherlands
44 */
45
46 package org.melati.poem.util;
47
48 import java.util.Enumeration;
49
50 /**
51 * An <code>Enumeration</code> that encapsulates another and
52 * translates each element according to an abstract mapping function.
53 * <p>
54 * Implementations must provide {@link #mapped(Object)}.
55 */
56 public abstract class MappedEnumeration<T,I> implements Enumeration<T> {
57
58 private Enumeration<I> enumeration;
59
60 /**
61 * Wrapper Constructor given Enumeration to wrap.
62 * @param enumeration Enumeration to wrap
63 */
64 public MappedEnumeration(Enumeration<I> enumeration) {
65 if (enumeration == null) throw new NullPointerException();
66 this.enumeration = enumeration;
67 }
68
69 /**
70 * {@inheritDoc}
71 * @see java.util.Enumeration#hasMoreElements()
72 */
73 public boolean hasMoreElements() {
74 return enumeration.hasMoreElements();
75 }
76
77 /**
78 * @param element the element of the Enumeration to act on
79 * @return the element after transformation
80 */
81 protected abstract T mapped(I element);
82
83 /**
84 * {@inheritDoc}
85 * @see java.util.Enumeration#nextElement()
86 */
87 public T nextElement() {
88 return mapped(enumeration.nextElement());
89 }
90 }