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Java > Open Source Codes > org > joda > time > field > UnsupportedDurationField


1 /*
2  * Copyright 2001-2005 Stephen Colebourne
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.joda.time.field;
17
18 import java.io.Serializable JavaDoc;
19 import java.util.HashMap JavaDoc;
20 import org.joda.time.DurationField;
21 import org.joda.time.DurationFieldType;
22
23 /**
24  * A placeholder implementation to use when a duration field is not supported.
25  * <p>
26  * UnsupportedDurationField is thread-safe and immutable.
27  *
28  * @author Brian S O'Neill
29  * @since 1.0
30  */
31 public final class UnsupportedDurationField extends DurationField implements Serializable JavaDoc {
32
33     /** Serialization lock. */
34     private static final long serialVersionUID = -6390301302770925357L;
35
36     /** The cache of unsupported duration field instances */
37     private static HashMap JavaDoc cCache;
38
39     /**
40      * Gets an instance of UnsupportedDurationField for a specific named field.
41      * The returned instance is cached.
42      *
43      * @param type the type to obtain
44      * @return the instance
45      */
46     public static synchronized UnsupportedDurationField getInstance(DurationFieldType type) {
47         UnsupportedDurationField field;
48         if (cCache == null) {
49             cCache = new HashMap JavaDoc(7);
50             field = null;
51         } else {
52             field = (UnsupportedDurationField) cCache.get(type);
53         }
54         if (field == null) {
55             field = new UnsupportedDurationField(type);
56             cCache.put(type, field);
57         }
58         return field;
59     }
60
61     /** The name of the field */
62     private final DurationFieldType iType;
63
64     /**
65      * Constructor.
66      *
67      * @param type the type to use
68      */
69     private UnsupportedDurationField(DurationFieldType type) {
70         iType = type;
71     }
72
73     //-----------------------------------------------------------------------
74 // Design note: Simple Accessors return a suitable value, but methods
75 // intended to perform calculations throw an UnsupportedOperationException.
76
77     public final DurationFieldType getType() {
78         return iType;
79     }
80
81     public String JavaDoc getName() {
82         return iType.getName();
83     }
84
85     /**
86      * This field is not supported.
87      *
88      * @return false always
89      */
90     public boolean isSupported() {
91         return false;
92     }
93
94     /**
95      * This field is precise.
96      *
97      * @return true always
98      */
99     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 JavaDoc 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 JavaDoc 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 JavaDoc toString() {
264         return "UnsupportedDurationField[" + getName() + ']';
265     }
266
267     /**
268      * Ensure proper singleton serialization
269      */
270     private Object JavaDoc readResolve() {
271         return getInstance(iType);
272     }
273
274     private UnsupportedOperationException JavaDoc unsupported() {
275         return new UnsupportedOperationException JavaDoc(iType + " field is unsupported");
276     }
277
278 }
279
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