1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.collections.iterators;
18
19 import java.util.NoSuchElementException;
20
21 /**
22 * Provides an implementation of an empty iterator.
23 *
24 * @since 3.1
25 * @version $Id: AbstractEmptyIterator.java 1429905 2013-01-07 17:15:14Z ggregory $
26 */
27 abstract class AbstractEmptyIterator<E> {
28
29 /**
30 * Constructor.
31 */
32 protected AbstractEmptyIterator() {
33 super();
34 }
35
36 public boolean hasNext() {
37 return false;
38 }
39
40 public E next() {
41 throw new NoSuchElementException("Iterator contains no elements");
42 }
43
44 public boolean hasPrevious() {
45 return false;
46 }
47
48 public E previous() {
49 throw new NoSuchElementException("Iterator contains no elements");
50 }
51
52 public int nextIndex() {
53 return 0;
54 }
55
56 public int previousIndex() {
57 return -1;
58 }
59
60 public void add(final E obj) {
61 throw new UnsupportedOperationException("add() not supported for empty Iterator");
62 }
63
64 public void set(final E obj) {
65 throw new IllegalStateException("Iterator contains no elements");
66 }
67
68 public void remove() {
69 throw new IllegalStateException("Iterator contains no elements");
70 }
71
72 public void reset() {
73 // do nothing
74 }
75
76 }