01: /*
02: * Copyright 2004 The Apache Software Foundation
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
10: * Unless required by applicable law or agreed to in writing, software
11: * distributed under the License is distributed on an "AS IS" BASIS,
12: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13: * See the License for the specific language governing permissions and
14: * limitations under the License.
15: */
16: package org.apache.commons.collections.iterators;
17:
18: import java.util.NoSuchElementException;
19:
20: /**
21: * Provides an implementation of an empty iterator.
22: *
23: * @since Commons Collections 3.1
24: * @version $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
25: *
26: * @author Stephen Colebourne
27: */
28: abstract class AbstractEmptyIterator {
29:
30: /**
31: * Constructor.
32: */
33: protected AbstractEmptyIterator() {
34: super ();
35: }
36:
37: public boolean hasNext() {
38: return false;
39: }
40:
41: public Object next() {
42: throw new NoSuchElementException(
43: "Iterator contains no elements");
44: }
45:
46: public boolean hasPrevious() {
47: return false;
48: }
49:
50: public Object previous() {
51: throw new NoSuchElementException(
52: "Iterator contains no elements");
53: }
54:
55: public int nextIndex() {
56: return 0;
57: }
58:
59: public int previousIndex() {
60: return -1;
61: }
62:
63: public void add(Object obj) {
64: throw new UnsupportedOperationException(
65: "add() not supported for empty Iterator");
66: }
67:
68: public void set(Object obj) {
69: throw new IllegalStateException("Iterator contains no elements");
70: }
71:
72: public void remove() {
73: throw new IllegalStateException("Iterator contains no elements");
74: }
75:
76: public Object getKey() {
77: throw new IllegalStateException("Iterator contains no elements");
78: }
79:
80: public Object getValue() {
81: throw new IllegalStateException("Iterator contains no elements");
82: }
83:
84: public Object setValue(Object value) {
85: throw new IllegalStateException("Iterator contains no elements");
86: }
87:
88: public void reset() {
89: // do nothing
90: }
91:
92: }
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