001    /*
002     *  Copyright 2001-2005 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    import org.joda.time.DurationField;
021    import org.joda.time.DurationFieldType;
022    
023    /**
024     * A placeholder implementation to use when a duration field is not supported.
025     * <p>
026     * UnsupportedDurationField is thread-safe and immutable.
027     *
028     * @author Brian S O'Neill
029     * @since 1.0
030     */
031    public final class UnsupportedDurationField extends DurationField implements Serializable {
032    
033        /** Serialization lock. */
034        private static final long serialVersionUID = -6390301302770925357L;
035    
036        /** The cache of unsupported duration field instances */
037        private static HashMap cCache;
038    
039        /**
040         * Gets an instance of UnsupportedDurationField for a specific named field.
041         * The returned instance is cached.
042         * 
043         * @param type  the type to obtain
044         * @return the instance
045         */
046        public static synchronized UnsupportedDurationField getInstance(DurationFieldType type) {
047            UnsupportedDurationField field;
048            if (cCache == null) {
049                cCache = new HashMap(7);
050                field = null;
051            } else {
052                field = (UnsupportedDurationField) cCache.get(type);
053            }
054            if (field == null) {
055                field = new UnsupportedDurationField(type);
056                cCache.put(type, field);
057            }
058            return field;
059        }
060    
061        /** The name of the field */
062        private final DurationFieldType iType;
063    
064        /**
065         * Constructor.
066         * 
067         * @param type  the type to use
068         */
069        private UnsupportedDurationField(DurationFieldType type) {
070            iType = type;
071        }
072    
073        //-----------------------------------------------------------------------
074        // Design note: Simple Accessors return a suitable value, but methods
075        // intended to perform calculations throw an UnsupportedOperationException.
076    
077        public final DurationFieldType getType() {
078            return iType;
079        }
080    
081        public String getName() {
082            return iType.getName();
083        }
084    
085        /**
086         * This field is not supported.
087         *
088         * @return false always
089         */
090        public boolean isSupported() {
091            return false;
092        }
093    
094        /**
095         * This field is precise.
096         * 
097         * @return true always
098         */
099        public boolean isPrecise() {
100            return true;
101        }
102    
103        /**
104         * Always throws UnsupportedOperationException
105         *
106         * @throws UnsupportedOperationException
107         */
108        public int getValue(long duration) {
109            throw unsupported();
110        }
111    
112        /**
113         * Always throws UnsupportedOperationException
114         *
115         * @throws UnsupportedOperationException
116         */
117        public long getValueAsLong(long duration) {
118            throw unsupported();
119        }
120    
121        /**
122         * Always throws UnsupportedOperationException
123         *
124         * @throws UnsupportedOperationException
125         */
126        public int getValue(long duration, long instant) {
127            throw unsupported();
128        }
129    
130        /**
131         * Always throws UnsupportedOperationException
132         *
133         * @throws UnsupportedOperationException
134         */
135        public long getValueAsLong(long duration, long instant) {
136            throw unsupported();
137        }
138    
139        /**
140         * Always throws UnsupportedOperationException
141         *
142         * @throws UnsupportedOperationException
143         */
144        public long getMillis(int value) {
145            throw unsupported();
146        }
147    
148        /**
149         * Always throws UnsupportedOperationException
150         *
151         * @throws UnsupportedOperationException
152         */
153        public long getMillis(long value) {
154            throw unsupported();
155        }
156    
157        /**
158         * Always throws UnsupportedOperationException
159         *
160         * @throws UnsupportedOperationException
161         */
162        public long getMillis(int value, long instant) {
163            throw unsupported();
164        }
165    
166        /**
167         * Always throws UnsupportedOperationException
168         *
169         * @throws UnsupportedOperationException
170         */
171        public long getMillis(long value, long instant) {
172            throw unsupported();
173        }
174    
175        /**
176         * Always throws UnsupportedOperationException
177         *
178         * @throws UnsupportedOperationException
179         */
180        public long add(long instant, int value) {
181            throw unsupported();
182        }
183    
184        /**
185         * Always throws UnsupportedOperationException
186         *
187         * @throws UnsupportedOperationException
188         */
189        public long add(long instant, long value) {
190            throw unsupported();
191        }
192    
193        /**
194         * Always throws UnsupportedOperationException
195         *
196         * @throws UnsupportedOperationException
197         */
198        public int getDifference(long minuendInstant, long subtrahendInstant) {
199            throw unsupported();
200        }
201    
202        /**
203         * Always throws UnsupportedOperationException
204         *
205         * @throws UnsupportedOperationException
206         */
207        public long getDifferenceAsLong(long minuendInstant, long subtrahendInstant) {
208            throw unsupported();
209        }
210    
211        /**
212         * Always returns zero.
213         *
214         * @return zero always
215         */
216        public long getUnitMillis() {
217            return 0;
218        }
219    
220        /**
221         * Always returns zero, indicating that sort order is not relevent.
222         *
223         * @return zero always
224         */
225        public int compareTo(Object durationField) {
226            return 0;
227        }
228    
229        //------------------------------------------------------------------------
230        /**
231         * Compares this duration field to another.
232         * 
233         * @param obj  the object to compare to
234         * @return true if equal
235         */
236        public boolean equals(Object obj) {
237            if (this == obj) {
238                return true;
239            } else if (obj instanceof UnsupportedDurationField) {
240                UnsupportedDurationField other = (UnsupportedDurationField) obj;
241                if (other.getName() == null) {
242                    return (getName() == null);
243                }
244                return (other.getName().equals(getName()));
245            }
246            return false;
247        }
248    
249        /**
250         * Gets a suitable hashcode.
251         * 
252         * @return the hashcode
253         */
254        public int hashCode() {
255            return getName().hashCode();
256        }
257    
258        /**
259         * Get a suitable debug string.
260         * 
261         * @return debug string
262         */
263        public String toString() {
264            return "UnsupportedDurationField[" + getName() + ']';
265        }
266    
267        /**
268         * Ensure proper singleton serialization
269         */
270        private Object readResolve() {
271            return getInstance(iType);
272        }
273    
274        private UnsupportedOperationException unsupported() {
275            return new UnsupportedOperationException(iType + " field is unsupported");
276        }
277    
278    }