001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.collections.primitives;
018
019 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharIterator;
020 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharList;
021 import org.apache.commons.collections.primitives.decorators.UnmodifiableCharListIterator;
022
023 /**
024 * This class consists exclusively of static methods that operate on or
025 * return CharCollections.
026 * <p>
027 * The methods of this class all throw a NullPoCharerException if the
028 * provided collection is null.
029 *
030 * @version $Revision: 480460 $ $Date: 2006-11-29 09:14:21 +0100 (Wed, 29 Nov 2006) $
031 *
032 * @author Rodney Waldhoff
033 */
034 public final class CharCollections {
035
036 /**
037 * Returns an unmodifiable CharList containing only the specified element.
038 * @param value the single value
039 * @return an unmodifiable CharList containing only the specified element.
040 */
041 public static CharList singletonCharList(char value) {
042 // TODO: a specialized implementation of CharList may be more performant
043 CharList list = new ArrayCharList(1);
044 list.add(value);
045 return UnmodifiableCharList.wrap(list);
046 }
047
048 /**
049 * Returns an unmodifiable CharIterator containing only the specified element.
050 * @param value the single value
051 * @return an unmodifiable CharIterator containing only the specified element.
052 */
053 public static CharIterator singletonCharIterator(char value) {
054 return singletonCharList(value).iterator();
055 }
056
057 /**
058 * Returns an unmodifiable CharListIterator containing only the specified element.
059 * @param value the single value
060 * @return an unmodifiable CharListIterator containing only the specified element.
061 */
062 public static CharListIterator singletonCharListIterator(char value) {
063 return singletonCharList(value).listIterator();
064 }
065
066 /**
067 * Returns an unmodifiable version of the given non-null CharList.
068 * @param list the non-null CharList to wrap in an unmodifiable decorator
069 * @return an unmodifiable version of the given non-null CharList
070 * @throws NullPointerException if the given CharList is null
071 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableCharList#wrap
072 */
073 public static CharList unmodifiableCharList(CharList list) throws NullPointerException {
074 if(null == list) {
075 throw new NullPointerException();
076 }
077 return UnmodifiableCharList.wrap(list);
078 }
079
080 /**
081 * Returns an unmodifiable version of the given non-null CharIterator.
082 * @param iter the non-null CharIterator to wrap in an unmodifiable decorator
083 * @return an unmodifiable version of the given non-null CharIterator
084 * @throws NullPointerException if the given CharIterator is null
085 * @see org.apache.commons.collections.primitives.decorators.UnmodifiableCharIterator#wrap
086 */
087 public static CharIterator unmodifiableCharIterator(CharIterator iter) {
088 if(null == iter) {
089 throw new NullPointerException();
090 }
091 return UnmodifiableCharIterator.wrap(iter);
092 }
093
094 /**
095 * Returns an unmodifiable version of the given non-null CharListIterator.
096 * @param iter the non-null CharListIterator to wrap in an unmodifiable decorator
097 * @return an unmodifiable version of the given non-null CharListIterator
098 * @throws NullPointerException if the given CharListIterator is null
099 * @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 }