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Java > Open Source Codes > org > joda > time > DurationFieldType


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;
17
18 import java.io.Serializable JavaDoc;
19
20 /**
21  * Identifies a duration field, such as years or minutes, in a chronology-neutral way.
22  * <p>
23  * A duration field type defines the type of the field, such as hours.
24  * If does not directly enable any calculations, however it does provide a
25  * {@link #getField(Chronology)} method that returns the actual calculation engine
26  * for a particular chronology.
27  * <p>
28  * Instances of <code>DurationFieldType</code> are singletons.
29  * They can be compared using <code>==</code>.
30  * <p>
31  * If required, you can create your own field, for example a quarters.
32  * You must create a subclass of <code>DurationFieldType</code> that defines the field type.
33  * This class returns the actual calculation engine from {@link #getField(Chronology)}.
34  *
35  * @author Stephen Colebourne
36  * @author Brian S O'Neill
37  * @since 1.0
38  */
39 public abstract class DurationFieldType implements Serializable JavaDoc {
40
41     /** Serialization version */
42     private static final long serialVersionUID = 8765135187319L;
43
44     // Ordinals for standard field types.
45 static final byte
46         ERAS = 1,
47         CENTURIES = 2,
48         WEEKYEARS = 3,
49         YEARS = 4,
50         MONTHS = 5,
51         WEEKS = 6,
52         DAYS = 7,
53         HALFDAYS = 8,
54         HOURS = 9,
55         MINUTES = 10,
56         SECONDS = 11,
57         MILLIS = 12;
58
59     /** The eras field type. */
60     static final DurationFieldType ERAS_TYPE = new StandardDurationFieldType("eras", ERAS);
61     /** The centuries field type. */
62     static final DurationFieldType CENTURIES_TYPE = new StandardDurationFieldType("centuries", CENTURIES);
63     /** The weekyears field type. */
64     static final DurationFieldType WEEKYEARS_TYPE = new StandardDurationFieldType("weekyears", WEEKYEARS);
65     /** The years field type. */
66     static final DurationFieldType YEARS_TYPE = new StandardDurationFieldType("years", YEARS);
67     /** The months field type. */
68     static final DurationFieldType MONTHS_TYPE = new StandardDurationFieldType("months", MONTHS);
69     /** The weeks field type. */
70     static final DurationFieldType WEEKS_TYPE = new StandardDurationFieldType("weeks", WEEKS);
71     /** The days field type. */
72     static final DurationFieldType DAYS_TYPE = new StandardDurationFieldType("days", DAYS);
73     /** The halfdays field type. */
74     static final DurationFieldType HALFDAYS_TYPE = new StandardDurationFieldType("halfdays", HALFDAYS);
75     /** The hours field type. */
76     static final DurationFieldType HOURS_TYPE = new StandardDurationFieldType("hours", HOURS);
77     /** The minutes field type. */
78     static final DurationFieldType MINUTES_TYPE = new StandardDurationFieldType("minutes", MINUTES);
79     /** The seconds field type. */
80     static final DurationFieldType SECONDS_TYPE = new StandardDurationFieldType("seconds", SECONDS);
81     /** The millis field type. */
82     static final DurationFieldType MILLIS_TYPE = new StandardDurationFieldType("millis", MILLIS);
83
84     /** The name of the field type. */
85     private final String JavaDoc iName;
86
87     //-----------------------------------------------------------------------
88 /**
89      * Constructor.
90      *
91      * @param name the name to use, which by convention, are plural.
92      */
93     protected DurationFieldType(String JavaDoc name) {
94         super();
95         iName = name;
96     }
97
98     //-----------------------------------------------------------------------
99 /**
100      * Get the millis field type.
101      *
102      * @return the DateTimeFieldType constant
103      */
104     public static DurationFieldType millis() {
105         return MILLIS_TYPE;
106     }
107
108     /**
109      * Get the seconds field type.
110      *
111      * @return the DateTimeFieldType constant
112      */
113     public static DurationFieldType seconds() {
114         return SECONDS_TYPE;
115     }
116
117     /**
118      * Get the minutes field type.
119      *
120      * @return the DateTimeFieldType constant
121      */
122     public static DurationFieldType minutes() {
123         return MINUTES_TYPE;
124     }
125
126     /**
127      * Get the hours field type.
128      *
129      * @return the DateTimeFieldType constant
130      */
131     public static DurationFieldType hours() {
132         return HOURS_TYPE;
133     }
134
135     /**
136      * Get the halfdays field type.
137      *
138      * @return the DateTimeFieldType constant
139      */
140     public static DurationFieldType halfdays() {
141         return HALFDAYS_TYPE;
142     }
143
144     //-----------------------------------------------------------------------
145 /**
146      * Get the days field type.
147      *
148      * @return the DateTimeFieldType constant
149      */
150     public static DurationFieldType days() {
151         return DAYS_TYPE;
152     }
153
154     /**
155      * Get the weeks field type.
156      *
157      * @return the DateTimeFieldType constant
158      */
159     public static DurationFieldType weeks() {
160         return WEEKS_TYPE;
161     }
162
163     /**
164      * Get the weekyears field type.
165      *
166      * @return the DateTimeFieldType constant
167      */
168     public static DurationFieldType weekyears() {
169         return WEEKYEARS_TYPE;
170     }
171
172     /**
173      * Get the months field type.
174      *
175      * @return the DateTimeFieldType constant
176      */
177     public static DurationFieldType months() {
178         return MONTHS_TYPE;
179     }
180
181     /**
182      * Get the years field type.
183      *
184      * @return the DateTimeFieldType constant
185      */
186     public static DurationFieldType years() {
187         return YEARS_TYPE;
188     }
189
190     /**
191      * Get the centuries field type.
192      *
193      * @return the DateTimeFieldType constant
194      */
195     public static DurationFieldType centuries() {
196         return CENTURIES_TYPE;
197     }
198
199     /**
200      * Get the eras field type.
201      *
202      * @return the DateTimeFieldType constant
203      */
204     public static DurationFieldType eras() {
205         return ERAS_TYPE;
206     }
207
208     //-----------------------------------------------------------------------
209 /**
210      * Get the name of the field.
211      * By convention, names are plural.
212      *
213      * @return field name
214      */
215     public String JavaDoc getName() {
216         return iName;
217     }
218
219     /**
220      * Gets a suitable field for this type from the given Chronology.
221      *
222      * @param chronology the chronology to use, null means ISOChronology in default zone
223      * @return a suitable field
224      */
225     public abstract DurationField getField(Chronology chronology);
226
227     /**
228      * Checks whether this field supported in the given Chronology.
229      *
230      * @param chronology the chronology to use, null means ISOChronology in default zone
231      * @return true if supported
232      */
233     public boolean isSupported(Chronology chronology) {
234         return getField(chronology).isSupported();
235     }
236
237     /**
238      * Get a suitable debug string.
239      *
240      * @return debug string
241      */
242     public String JavaDoc toString() {
243         return getName();
244     }
245
246     private static class StandardDurationFieldType extends DurationFieldType {
247         /** Serialization version */
248         private static final long serialVersionUID = 31156755687123L;
249
250         /** The ordinal of the standard field type, for switch statements */
251         private final byte iOrdinal;
252
253         /**
254          * Constructor.
255          *
256          * @param name the name to use
257          */
258         StandardDurationFieldType(String JavaDoc name, byte ordinal) {
259             super(name);
260             iOrdinal = ordinal;
261         }
262
263         public DurationField getField(Chronology chronology) {
264             chronology = DateTimeUtils.getChronology(chronology);
265             
266             switch (iOrdinal) {
267                 case ERAS:
268                     return chronology.eras();
269                 case CENTURIES:
270                     return chronology.centuries();
271                 case WEEKYEARS:
272                     return chronology.weekyears();
273                 case YEARS:
274                     return chronology.years();
275                 case MONTHS:
276                     return chronology.months();
277                 case WEEKS:
278                     return chronology.weeks();
279                 case DAYS:
280                     return chronology.days();
281                 case HALFDAYS:
282                     return chronology.halfdays();
283                 case HOURS:
284                     return chronology.hours();
285                 case MINUTES:
286                     return chronology.minutes();
287                 case SECONDS:
288                     return chronology.seconds();
289                 case MILLIS:
290                     return chronology.millis();
291                 default:
292                     // Shouldn't happen.
293 throw new InternalError JavaDoc();
294             }
295         }
296
297         /**
298          * Ensure a singleton is returned.
299          *
300          * @return the singleton type
301          */
302         private Object JavaDoc readResolve() {
303             switch (iOrdinal) {
304                 case ERAS:
305                     return ERAS_TYPE;
306                 case CENTURIES:
307                     return CENTURIES_TYPE;
308                 case WEEKYEARS:
309                     return WEEKYEARS_TYPE;
310                 case YEARS:
311                     return YEARS_TYPE;
312                 case MONTHS:
313                     return MONTHS_TYPE;
314                 case WEEKS:
315                     return WEEKS_TYPE;
316                 case DAYS:
317                     return DAYS_TYPE;
318                 case HALFDAYS:
319                     return HALFDAYS_TYPE;
320                 case HOURS:
321                     return HOURS_TYPE;
322                 case MINUTES:
323                     return MINUTES_TYPE;
324                 case SECONDS:
325                     return SECONDS_TYPE;
326                 case MILLIS:
327                     return MILLIS_TYPE;
328                 default:
329                     // Shouldn't happen.
330 return this;
331             }
332         }
333
334     }
335 }
336
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