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    }