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.UnmodifiableLongIterator;
020    import org.apache.commons.collections.primitives.decorators.UnmodifiableLongList;
021    import org.apache.commons.collections.primitives.decorators.UnmodifiableLongListIterator;
022    
023    /**
024     * This class consists exclusively of static methods that operate on or
025     * return LongCollections.
026     * <p>
027     * The methods of this class all throw a NullPoLongerException 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 LongCollections {
035    
036        /**
037         * Returns an unmodifiable LongList containing only the specified element.
038         * @param value the single value
039         * @return an unmodifiable LongList containing only the specified element.
040         */    
041        public static LongList singletonLongList(long value) {
042            // TODO: a specialized implementation of LongList may be more performant
043            LongList list = new ArrayLongList(1);
044            list.add(value);
045            return UnmodifiableLongList.wrap(list);
046        }
047    
048        /**
049         * Returns an unmodifiable LongIterator containing only the specified element.
050         * @param value the single value
051         * @return an unmodifiable LongIterator containing only the specified element.
052         */    
053        public static LongIterator singletonLongIterator(long value) {
054            return singletonLongList(value).iterator();
055        }
056    
057        /**
058         * Returns an unmodifiable LongListIterator containing only the specified element.
059         * @param value the single value
060         * @return an unmodifiable LongListIterator containing only the specified element.
061         */    
062        public static LongListIterator singletonLongListIterator(long value) {
063            return singletonLongList(value).listIterator();
064        }
065    
066        /**
067         * Returns an unmodifiable version of the given non-null LongList.
068         * @param list the non-null LongList to wrap in an unmodifiable decorator
069         * @return an unmodifiable version of the given non-null LongList
070         * @throws NullPointerException if the given LongList is null
071         * @see org.apache.commons.collections.primitives.decorators.UnmodifiableLongList#wrap
072         */    
073        public static LongList unmodifiableLongList(LongList list) throws NullPointerException {
074            if(null == list) {
075                throw new NullPointerException();
076            }
077            return UnmodifiableLongList.wrap(list);
078        }
079        
080        /**
081         * Returns an unmodifiable version of the given non-null LongIterator.
082         * @param iter the non-null LongIterator to wrap in an unmodifiable decorator
083         * @return an unmodifiable version of the given non-null LongIterator
084         * @throws NullPointerException if the given LongIterator is null
085         * @see org.apache.commons.collections.primitives.decorators.UnmodifiableLongIterator#wrap
086         */    
087        public static LongIterator unmodifiableLongIterator(LongIterator iter) {
088            if(null == iter) {
089                throw new NullPointerException();
090            }
091            return UnmodifiableLongIterator.wrap(iter);
092        }
093            
094        /**
095         * Returns an unmodifiable version of the given non-null LongListIterator.
096         * @param iter the non-null LongListIterator to wrap in an unmodifiable decorator
097         * @return an unmodifiable version of the given non-null LongListIterator
098         * @throws NullPointerException if the given LongListIterator is null
099         * @see org.apache.commons.collections.primitives.decorators.UnmodifiableLongListIterator#wrap
100         */    
101        public static LongListIterator unmodifiableLongListIterator(LongListIterator iter) {
102            if(null == iter) {
103                throw new NullPointerException();
104            }
105            return UnmodifiableLongListIterator.wrap(iter);
106        }
107        
108        /**
109         * Returns an unmodifiable, empty LongList.
110         * @return an unmodifiable, empty LongList.
111         * @see #EMPTY_LONG_LIST
112         */    
113        public static LongList getEmptyLongList() {
114            return EMPTY_LONG_LIST;
115        }
116        
117        /**
118         * Returns an unmodifiable, empty LongIterator
119         * @return an unmodifiable, empty LongIterator.
120         * @see #EMPTY_LONG_ITERATOR
121         */    
122        public static LongIterator getEmptyLongIterator() {
123            return EMPTY_LONG_ITERATOR;
124        }
125        
126        /**
127         * Returns an unmodifiable, empty LongListIterator
128         * @return an unmodifiable, empty LongListIterator.
129         * @see #EMPTY_LONG_LIST_ITERATOR
130         */    
131        public static LongListIterator getEmptyLongListIterator() {
132            return EMPTY_LONG_LIST_ITERATOR;
133        }    
134    
135        /**
136         * An unmodifiable, empty LongList
137         * @see #getEmptyLongList
138         */    
139        public static final LongList EMPTY_LONG_LIST = unmodifiableLongList(new ArrayLongList(0));
140    
141        /**
142         * An unmodifiable, empty LongIterator
143         * @see #getEmptyLongIterator
144         */    
145        public static final LongIterator EMPTY_LONG_ITERATOR = unmodifiableLongIterator(EMPTY_LONG_LIST.iterator());
146    
147        /**
148         * An unmodifiable, empty LongListIterator
149         * @see #getEmptyLongListIterator
150         */    
151        public static final LongListIterator EMPTY_LONG_LIST_ITERATOR = unmodifiableLongListIterator(EMPTY_LONG_LIST.listIterator());
152    }