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 import java.util.NoSuchElementException;
50
51 /**
52 * An <code>Enumeration</code> representing the first <code>n</code>
53 * elements of another <code>Enumeration</code>.
54 */
55 public class LimitedEnumeration<T> implements SkipEnumeration<T>{
56
57 private Enumeration<T> base;
58 private int limit;
59 private int seen = 0;
60
61 /**
62 * Constructor.
63 * @param base the underlying Enumeration
64 * @param limit the excluded limit
65 */
66 public LimitedEnumeration(Enumeration<T> base, int limit) {
67 this.base = base;
68 this.limit = limit;
69 }
70
71 /**
72 * {@inheritDoc}
73 * @see java.util.Enumeration#hasMoreElements()
74 */
75 public synchronized boolean hasMoreElements() {
76 return seen < limit && base.hasMoreElements();
77 }
78
79 /**
80 * {@inheritDoc}
81 * @see java.util.Enumeration#nextElement()
82 */
83 public synchronized T nextElement() throws NoSuchElementException {
84 if (seen >= limit)
85 throw new NoSuchElementException();
86 T it = base.nextElement();
87 ++seen;
88 return it;
89 }
90
91 /**
92 * {@inheritDoc}
93 * @see org.melati.poem.util.SkipEnumeration#skip()
94 */
95 public synchronized void skip() throws NoSuchElementException {
96 if (seen >= limit)
97 throw new NoSuchElementException();
98 if (base instanceof SkipEnumeration)
99 ((SkipEnumeration<T>)base).skip();
100 else
101 base.nextElement();
102
103 ++seen;
104 }
105 }