001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2006, by Object Refinery Limited and Contributors.
006     *
007     * Project Info:  http://www.jfree.org/jfreechart/index.html
008     *
009     * This library is free software; you can redistribute it and/or modify it 
010     * under the terms of the GNU Lesser General Public License as published by 
011     * the Free Software Foundation; either version 2.1 of the License, or 
012     * (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but 
015     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016     * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017     * License for more details.
018     *
019     * You should have received a copy of the GNU Lesser General Public
020     * License along with this library; if not, write to the Free Software
021     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022     * USA.  
023     *
024     * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025     * in the United States and other countries.]
026     *
027     * ----------------------
028     * RegularTimePeriod.java
029     * ----------------------
030     * (C) Copyright 2001-2006, by Object Refinery Limited.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: RegularTimePeriod.java,v 1.6.2.2 2006/10/06 14:00:15 mungady Exp $
036     *
037     * Changes
038     * -------
039     * 11-Oct-2001 : Version 1 (DG);
040     * 26-Feb-2002 : Changed getStart(), getMiddle() and getEnd() methods to 
041     *               evaluate with reference to a particular time zone (DG);
042     * 29-May-2002 : Implemented MonthConstants interface, so that these constants 
043     *               are conveniently available (DG);
044     * 10-Sep-2002 : Added getSerialIndex() method (DG);
045     * 10-Jan-2003 : Renamed TimePeriod --> RegularTimePeriod (DG);
046     * 13-Mar-2003 : Moved to com.jrefinery.data.time package (DG);
047     * 29-Apr-2004 : Changed getMiddleMillisecond() methods to fix bug 943985 (DG);
048     * 25-Nov-2004 : Added utility methods (DG);
049     * ------------- JFREECHART 1.0.x ---------------------------------------------
050     * 06-Oct-2006 : Deprecated the WORKING_CALENDAR field and several methods,
051     *               added new peg() method (DG);
052     *
053     */
054    
055    package org.jfree.data.time;
056    
057    import java.lang.reflect.Constructor;
058    import java.util.Calendar;
059    import java.util.Date;
060    import java.util.TimeZone;
061    
062    import org.jfree.date.MonthConstants;
063    
064    /**
065     * An abstract class representing a unit of time.  Convenient methods are 
066     * provided for calculating the next and previous time periods.  Conversion 
067     * methods are defined that return the first and last milliseconds of the time 
068     * period.  The results from these methods are timezone dependent.
069     * <P>
070     * This class is immutable, and all subclasses should be immutable also.
071     */
072    public abstract class RegularTimePeriod implements TimePeriod, Comparable, 
073                                                       MonthConstants {
074    
075        /**
076         * Creates a time period that includes the specified millisecond, assuming 
077         * the given time zone.
078         * 
079         * @param c  the time period class.
080         * @param millisecond  the time.
081         * @param zone  the time zone.
082         * 
083         * @return The time period.
084         */
085        public static RegularTimePeriod createInstance(Class c, Date millisecond, 
086                                                       TimeZone zone) {
087            RegularTimePeriod result = null;
088            try {
089                Constructor constructor = c.getDeclaredConstructor(
090                        new Class[] {Date.class, TimeZone.class});
091                result = (RegularTimePeriod) constructor.newInstance(
092                        new Object[] {millisecond, zone});
093            }
094            catch (Exception e) {
095                // do nothing, so null is returned            
096            }
097            return result;  
098        }
099        
100        /**
101         * Returns a subclass of {@link RegularTimePeriod} that is smaller than
102         * the specified class.
103         * 
104         * @param c  a subclass of {@link RegularTimePeriod}.
105         * 
106         * @return A class.
107         */
108        public static Class downsize(Class c) {
109            if (c.equals(Year.class)) {
110                return Quarter.class;
111            }
112            else if (c.equals(Quarter.class)) {
113                return Month.class;
114            }
115            else if (c.equals(Month.class)) {
116                return Day.class;
117            }
118            else if (c.equals(Day.class)) {
119                return Hour.class;
120            }
121            else if (c.equals(Hour.class)) {
122                return Minute.class;
123            }
124            else if (c.equals(Minute.class)) {
125                return Second.class;
126            }
127            else if (c.equals(Second.class)) {
128                return Millisecond.class;
129            }
130            else {
131                return Millisecond.class;
132            }
133        }
134        
135        /**
136         * Returns the time period preceding this one, or <code>null</code> if some
137         * lower limit has been reached.
138         *
139         * @return The previous time period (possibly <code>null</code>).
140         */
141        public abstract RegularTimePeriod previous();
142    
143        /**
144         * Returns the time period following this one, or <code>null</code> if some
145         * limit has been reached.
146         *
147         * @return The next time period (possibly <code>null</code>).
148         */
149        public abstract RegularTimePeriod next();
150    
151        /**
152         * Returns a serial index number for the time unit.
153         *
154         * @return The serial index number.
155         */
156        public abstract long getSerialIndex();
157    
158        //////////////////////////////////////////////////////////////////////////
159    
160        /** 
161         * The default time zone. 
162         */
163        public static final TimeZone DEFAULT_TIME_ZONE = TimeZone.getDefault();
164    
165        /** 
166         * A working calendar (recycle to avoid unnecessary object creation). 
167         * 
168         * @deprecated This was a bad idea, don't use it!
169         */
170        public static final Calendar WORKING_CALENDAR 
171            = Calendar.getInstance(DEFAULT_TIME_ZONE);
172    
173        /** 
174         * Recalculates the start date/time and end date/time for this time period 
175         * relative to the supplied calendar (which incorporates a time zone).
176         * 
177         * @param calendar  the calendar (<code>null</code> not permitted).
178         * 
179         * @since 1.0.3
180         */
181        public abstract void peg(Calendar calendar);
182        
183        /**
184         * Returns the date/time that marks the start of the time period.  This 
185         * method returns a new <code>Date</code> instance every time it is called.
186         *
187         * @return The start date/time.
188         * 
189         * @see #getFirstMillisecond()
190         */
191        public Date getStart() {
192            return new Date(getFirstMillisecond());
193        }
194    
195        /**
196         * Returns the date/time that marks the end of the time period.  This 
197         * method returns a new <code>Date</code> instance every time it is called.
198         *
199         * @return The end date/time.
200         * 
201         * @see #getLastMillisecond()
202         */
203        public Date getEnd() {
204            return new Date(getLastMillisecond());
205        }
206    
207        /**
208         * Returns the first millisecond of the time period.  This will be 
209         * determined relative to the time zone specified in the constructor, or
210         * in the calendar instance passed in the most recent call to the 
211         * {@link #peg(Calendar)} method.
212         *
213         * @return The first millisecond of the time period.
214         * 
215         * @see #getLastMillisecond()
216         */
217        public abstract long getFirstMillisecond();
218    
219        /**
220         * Returns the first millisecond of the time period, evaluated within a 
221         * specific time zone.
222         *
223         * @param zone  the time zone (<code>null</code> not permitted).
224         *
225         * @return The first millisecond of the time period.
226         * 
227         * @deprecated As of 1.0.3, you should avoid using this method (it creates
228         *     a new Calendar instance every time it is called).  You are advised
229         *     to call {@link #getFirstMillisecond(Calendar)} instead.
230         *     
231         * @see #getLastMillisecond(TimeZone)
232         */
233        public long getFirstMillisecond(TimeZone zone) {
234            Calendar calendar = Calendar.getInstance(zone);
235            return getFirstMillisecond(calendar);
236        }
237    
238        /**
239         * Returns the first millisecond of the time period, evaluated using the 
240         * supplied calendar (which incorporates a timezone).
241         *
242         * @param calendar  the calendar (<code>null</code> not permitted).
243         *
244         * @return The first millisecond of the time period.
245         * 
246         * @throws NullPointerException if <code>calendar,/code> is 
247         *     </code>null</code>.
248         *     
249         * @see #getLastMillisecond(Calendar)
250         */
251        public abstract long getFirstMillisecond(Calendar calendar);
252    
253        /**
254         * Returns the last millisecond of the time period.  This will be 
255         * determined relative to the time zone specified in the constructor, or
256         * in the calendar instance passed in the most recent call to the 
257         * {@link #peg(Calendar)} method.
258         *
259         * @return The last millisecond of the time period.
260         * 
261         * @see #getFirstMillisecond()
262         */
263        public abstract long getLastMillisecond();
264    
265        /**
266         * Returns the last millisecond of the time period, evaluated within a 
267         * specific time zone.
268         *
269         * @param zone  the time zone (<code>null</code> not permitted).
270         *
271         * @return The last millisecond of the time period.
272         * 
273         * @deprecated As of 1.0.3, you should avoid using this method (it creates
274         *     a new Calendar instance every time it is called).  You are advised
275         *     to call {@link #getLastMillisecond(Calendar)} instead.
276         *     
277         * @see #getFirstMillisecond(TimeZone)
278         */
279        public long getLastMillisecond(TimeZone zone) {
280            Calendar calendar = Calendar.getInstance(zone);
281            return getLastMillisecond(calendar);
282        }
283    
284        /**
285         * Returns the last millisecond of the time period, evaluated using the 
286         * supplied calendar (which incorporates a timezone).
287         *
288         * @param calendar  the calendar (<code>null</code> not permitted).
289         *
290         * @return The last millisecond of the time period.
291         * 
292         * @see #getFirstMillisecond(Calendar)
293         */
294        public abstract long getLastMillisecond(Calendar calendar);
295    
296        /**
297         * Returns the millisecond closest to the middle of the time period.
298         *
299         * @return The middle millisecond.
300         */
301        public long getMiddleMillisecond() {
302            long m1 = getFirstMillisecond();
303            long m2 = getLastMillisecond();
304            return m1 + (m2 - m1) / 2;
305        }
306    
307        /**
308         * Returns the millisecond closest to the middle of the time period,
309         * evaluated within a specific time zone.
310         *
311         * @param zone  the time zone (<code>null</code> not permitted).
312         *
313         * @return The middle millisecond.
314         * 
315         * @deprecated As of 1.0.3, you should avoid using this method (it creates
316         *     a new Calendar instance every time it is called).  You are advised
317         *     to call {@link #getMiddleMillisecond(Calendar)} instead.
318         */
319        public long getMiddleMillisecond(TimeZone zone) {
320            Calendar calendar = Calendar.getInstance(zone);
321            long m1 = getFirstMillisecond(calendar);
322            long m2 = getLastMillisecond(calendar);
323            return m1 + (m2 - m1) / 2;
324        }
325    
326        /**
327         * Returns the millisecond closest to the middle of the time period,
328         * evaluated using the supplied calendar (which incorporates a timezone).
329         *
330         * @param calendar  the calendar.
331         *
332         * @return The middle millisecond.
333         */
334        public long getMiddleMillisecond(Calendar calendar) {
335            long m1 = getFirstMillisecond(calendar);
336            long m2 = getLastMillisecond(calendar);
337            return m1 + (m2 - m1) / 2;
338        }
339    
340        /**
341         * Returns a string representation of the time period.
342         *
343         * @return The string.
344         */
345        public String toString() {
346            return String.valueOf(getStart());
347        }
348    
349    }