001    /*
002     *  Copyright 2001-2009 Stephen Colebourne
003     *
004     *  Licensed under the Apache License, Version 2.0 (the "License");
005     *  you may not use this file except in compliance with the License.
006     *  You may obtain a copy of the License at
007     *
008     *      http://www.apache.org/licenses/LICENSE-2.0
009     *
010     *  Unless required by applicable law or agreed to in writing, software
011     *  distributed under the License is distributed on an "AS IS" BASIS,
012     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     *  See the License for the specific language governing permissions and
014     *  limitations under the License.
015     */
016    package org.joda.time.field;
017    
018    import java.io.Serializable;
019    import java.util.HashMap;
020    
021    import org.joda.time.DurationField;
022    import org.joda.time.DurationFieldType;
023    
024    /**
025     * A placeholder implementation to use when a duration field is not supported.
026     * <p>
027     * UnsupportedDurationField is thread-safe and immutable.
028     *
029     * @author Brian S O'Neill
030     * @since 1.0
031     */
032    public final class UnsupportedDurationField extends DurationField implements Serializable {
033    
034        /** Serialization lock. */
035        private static final long serialVersionUID = -6390301302770925357L;
036    
037        /** The cache of unsupported duration field instances */
038        private static HashMap<DurationFieldType, UnsupportedDurationField> cCache;
039    
040        /**
041         * Gets an instance of UnsupportedDurationField for a specific named field.
042         * The returned instance is cached.
043         * 
044         * @param type  the type to obtain
045         * @return the instance
046         */
047        public static synchronized UnsupportedDurationField getInstance(DurationFieldType type) {
048            UnsupportedDurationField field;
049            if (cCache == null) {
050                cCache = new HashMap<DurationFieldType, UnsupportedDurationField>(7);
051                field = null;
052            } else {
053                field = cCache.get(type);
054            }
055            if (field == null) {
056                field = new UnsupportedDurationField(type);
057                cCache.put(type, field);
058            }
059            return field;
060        }
061    
062        /** The name of the field */
063        private final DurationFieldType iType;
064    
065        /**
066         * Constructor.
067         * 
068         * @param type  the type to use
069         */
070        private UnsupportedDurationField(DurationFieldType type) {
071            iType = type;
072        }
073    
074        //-----------------------------------------------------------------------
075        // Design note: Simple Accessors return a suitable value, but methods
076        // intended to perform calculations throw an UnsupportedOperationException.
077    
078        public final DurationFieldType getType() {
079            return iType;
080        }
081    
082        public String getName() {
083            return iType.getName();
084        }
085    
086        /**
087         * This field is not supported.
088         *
089         * @return false always
090         */
091        public boolean isSupported() {
092            return false;
093        }
094    
095        /**
096         * This field is precise.
097         * 
098         * @return true always
099         */
100        public boolean isPrecise() {
101            return true;
102        }
103    
104        /**
105         * Always throws UnsupportedOperationException
106         *
107         * @throws UnsupportedOperationException
108         */
109        public int getValue(long duration) {
110            throw unsupported();
111        }
112    
113        /**
114         * Always throws UnsupportedOperationException
115         *
116         * @throws UnsupportedOperationException
117         */
118        public long getValueAsLong(long duration) {
119            throw unsupported();
120        }
121    
122        /**
123         * Always throws UnsupportedOperationException
124         *
125         * @throws UnsupportedOperationException
126         */
127        public int getValue(long duration, long instant) {
128            throw unsupported();
129        }
130    
131        /**
132         * Always throws UnsupportedOperationException
133         *
134         * @throws UnsupportedOperationException
135         */
136        public long getValueAsLong(long duration, long instant) {
137            throw unsupported();
138        }
139    
140        /**
141         * Always throws UnsupportedOperationException
142         *
143         * @throws UnsupportedOperationException
144         */
145        public long getMillis(int value) {
146            throw unsupported();
147        }
148    
149        /**
150         * Always throws UnsupportedOperationException
151         *
152         * @throws UnsupportedOperationException
153         */
154        public long getMillis(long value) {
155            throw unsupported();
156        }
157    
158        /**
159         * Always throws UnsupportedOperationException
160         *
161         * @throws UnsupportedOperationException
162         */
163        public long getMillis(int value, long instant) {
164            throw unsupported();
165        }
166    
167        /**
168         * Always throws UnsupportedOperationException
169         *
170         * @throws UnsupportedOperationException
171         */
172        public long getMillis(long value, long instant) {
173            throw unsupported();
174        }
175    
176        /**
177         * Always throws UnsupportedOperationException
178         *
179         * @throws UnsupportedOperationException
180         */
181        public long add(long instant, int value) {
182            throw unsupported();
183        }
184    
185        /**
186         * Always throws UnsupportedOperationException
187         *
188         * @throws UnsupportedOperationException
189         */
190        public long add(long instant, long value) {
191            throw unsupported();
192        }
193    
194        /**
195         * Always throws UnsupportedOperationException
196         *
197         * @throws UnsupportedOperationException
198         */
199        public int getDifference(long minuendInstant, long subtrahendInstant) {
200            throw unsupported();
201        }
202    
203        /**
204         * Always throws UnsupportedOperationException
205         *
206         * @throws UnsupportedOperationException
207         */
208        public long getDifferenceAsLong(long minuendInstant, long subtrahendInstant) {
209            throw unsupported();
210        }
211    
212        /**
213         * Always returns zero.
214         *
215         * @return zero always
216         */
217        public long getUnitMillis() {
218            return 0;
219        }
220    
221        /**
222         * Always returns zero, indicating that sort order is not relevent.
223         *
224         * @return zero always
225         */
226        public int compareTo(DurationField durationField) {
227            return 0;
228        }
229    
230        //------------------------------------------------------------------------
231        /**
232         * Compares this duration field to another.
233         * 
234         * @param obj  the object to compare to
235         * @return true if equal
236         */
237        public boolean equals(Object obj) {
238            if (this == obj) {
239                return true;
240            } else if (obj instanceof UnsupportedDurationField) {
241                UnsupportedDurationField other = (UnsupportedDurationField) obj;
242                if (other.getName() == null) {
243                    return (getName() == null);
244                }
245                return (other.getName().equals(getName()));
246            }
247            return false;
248        }
249    
250        /**
251         * Gets a suitable hashcode.
252         * 
253         * @return the hashcode
254         */
255        public int hashCode() {
256            return getName().hashCode();
257        }
258    
259        /**
260         * Get a suitable debug string.
261         * 
262         * @return debug string
263         */
264        public String toString() {
265            return "UnsupportedDurationField[" + getName() + ']';
266        }
267    
268        /**
269         * Ensure proper singleton serialization
270         */
271        private Object readResolve() {
272            return getInstance(iType);
273        }
274    
275        private UnsupportedOperationException unsupported() {
276            return new UnsupportedOperationException(iType + " field is unsupported");
277        }
278    
279    }