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.primitives;
18
19 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharIterator;
20 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharList;
21 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharListIterator;
22
23 /**
24 * This class consists exclusively of static methods that operate on or
25 * return CharCollections.
26 * <p>
27 * The methods of this class all throw a NullPoCharerException if the
28 * provided collection is null.
29 *
30 * @version $Revision: 480460 $ $Date: 2006-11-29 03:14:21 -0500 (Wed, 29 Nov 2006) $
31 *
32 * @author Rodney Waldhoff
33 */
34 public final class CharCollections {
35
36 /**
37 * Returns an unmodifiable CharList containing only the specified element.
38 * @param value the single value
39 * @return an unmodifiable CharList containing only the specified element.
40 */
41 public static CharList singletonCharList(char value) {
42 // TODO: a specialized implementation of CharList may be more performant
43 CharList list = new ArrayCharList(1);
44 list.add(value);
45 return UnmodifiableCharList.wrap(list);
46 }
47
48 /**
49 * Returns an unmodifiable CharIterator containing only the specified element.
50 * @param value the single value
51 * @return an unmodifiable CharIterator containing only the specified element.
52 */
53 public static CharIterator singletonCharIterator(char value) {
54 return singletonCharList(value).iterator();
55 }
56
57 /**
58 * Returns an unmodifiable CharListIterator containing only the specified element.
59 * @param value the single value
60 * @return an unmodifiable CharListIterator containing only the specified element.
61 */
62 public static CharListIterator singletonCharListIterator(char value) {
63 return singletonCharList(value).listIterator();
64 }
65
66 /**
67 * Returns an unmodifiable version of the given non-null CharList.
68 * @param list the non-null CharList to wrap in an unmodifiable decorator
69 * @return an unmodifiable version of the given non-null CharList
70 * @throws NullPointerException if the given CharList is null
71 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableCharList#wrap
72 */
73 public static CharList unmodifiableCharList(CharList list) throws NullPointerException {
74 if(null == list) {
75 throw new NullPointerException();
76 }
77 return UnmodifiableCharList.wrap(list);
78 }
79
80 /**
81 * Returns an unmodifiable version of the given non-null CharIterator.
82 * @param iter the non-null CharIterator to wrap in an unmodifiable decorator
83 * @return an unmodifiable version of the given non-null CharIterator
84 * @throws NullPointerException if the given CharIterator is null
85 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableCharIterator#wrap
86 */
87 public static CharIterator unmodifiableCharIterator(CharIterator iter) {
88 if(null == iter) {
89 throw new NullPointerException();
90 }
91 return UnmodifiableCharIterator.wrap(iter);
92 }
93
94 /**
95 * Returns an unmodifiable version of the given non-null CharListIterator.
96 * @param iter the non-null CharListIterator to wrap in an unmodifiable decorator
97 * @return an unmodifiable version of the given non-null CharListIterator
98 * @throws NullPointerException if the given CharListIterator is null
99 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableCharListIterator#wrap
100 */
101 public static CharListIterator unmodifiableCharListIterator(CharListIterator iter) {
102 if(null == iter) {
103 throw new NullPointerException();
104 }
105 return UnmodifiableCharListIterator.wrap(iter);
106 }
107
108 /**
109 * Returns an unmodifiable, empty CharList.
110 * @return an unmodifiable, empty CharList.
111 * @see #EMPTY_CHAR_LIST
112 */
113 public static CharList getEmptyCharList() {
114 return EMPTY_CHAR_LIST;
115 }
116
117 /**
118 * Returns an unmodifiable, empty CharIterator
119 * @return an unmodifiable, empty CharIterator.
120 * @see #EMPTY_CHAR_ITERATOR
121 */
122 public static CharIterator getEmptyCharIterator() {
123 return EMPTY_CHAR_ITERATOR;
124 }
125
126 /**
127 * Returns an unmodifiable, empty CharListIterator
128 * @return an unmodifiable, empty CharListIterator.
129 * @see #EMPTY_CHAR_LIST_ITERATOR
130 */
131 public static CharListIterator getEmptyCharListIterator() {
132 return EMPTY_CHAR_LIST_ITERATOR;
133 }
134
135 /**
136 * An unmodifiable, empty CharList
137 * @see #getEmptyCharList
138 */
139 public static final CharList EMPTY_CHAR_LIST = unmodifiableCharList(new ArrayCharList(0));
140
141 /**
142 * An unmodifiable, empty CharIterator
143 * @see #getEmptyCharIterator
144 */
145 public static final CharIterator EMPTY_CHAR_ITERATOR = unmodifiableCharIterator(EMPTY_CHAR_LIST.iterator());
146
147 /**
148 * An unmodifiable, empty CharListIterator
149 * @see #getEmptyCharListIterator
150 */
151 public static final CharListIterator EMPTY_CHAR_LIST_ITERATOR = unmodifiableCharListIterator(EMPTY_CHAR_LIST.listIterator());
152 }