001/*
002 *  Copyright 2001-2010 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 */
016package org.joda.time;
017
018import org.joda.convert.FromString;
019import org.joda.convert.ToString;
020import org.joda.time.base.BaseSingleFieldPeriod;
021import org.joda.time.field.FieldUtils;
022import org.joda.time.format.ISOPeriodFormat;
023import org.joda.time.format.PeriodFormatter;
024
025/**
026 * An immutable time period representing a number of days.
027 * <p>
028 * <code>Days</code> is an immutable period that can only store days.
029 * It does not store years, months or hours for example. As such it is a
030 * type-safe way of representing a number of days in an application.
031 * <p>
032 * The number of days is set in the constructor, and may be queried using
033 * <code>getDays()</code>. Basic mathematical operations are provided -
034 * <code>plus()</code>, <code>minus()</code>, <code>multipliedBy()</code> and
035 * <code>dividedBy()</code>.
036 * <p>
037 * <code>Days</code> is thread-safe and immutable.
038 *
039 * @author Stephen Colebourne
040 * @since 1.4
041 */
042public final class Days extends BaseSingleFieldPeriod {
043
044    /** Constant representing zero days. */
045    public static final Days ZERO = new Days(0);
046    /** Constant representing one day. */
047    public static final Days ONE = new Days(1);
048    /** Constant representing two days. */
049    public static final Days TWO = new Days(2);
050    /** Constant representing three days. */
051    public static final Days THREE = new Days(3);
052    /** Constant representing four days. */
053    public static final Days FOUR = new Days(4);
054    /** Constant representing five days. */
055    public static final Days FIVE = new Days(5);
056    /** Constant representing six days. */
057    public static final Days SIX = new Days(6);
058    /** Constant representing seven days. */
059    public static final Days SEVEN = new Days(7);
060    /** Constant representing the maximum number of days that can be stored in this object. */
061    public static final Days MAX_VALUE = new Days(Integer.MAX_VALUE);
062    /** Constant representing the minimum number of days that can be stored in this object. */
063    public static final Days MIN_VALUE = new Days(Integer.MIN_VALUE);
064
065    /** The paser to use for this class. */
066    private static final PeriodFormatter PARSER = ISOPeriodFormat.standard().withParseType(PeriodType.days());
067    /** Serialization version. */
068    private static final long serialVersionUID = 87525275727380865L;
069
070    //-----------------------------------------------------------------------
071    /**
072     * Obtains an instance of <code>Days</code> that may be cached.
073     * <code>Days</code> is immutable, so instances can be cached and shared.
074     * This factory method provides access to shared instances.
075     *
076     * @param days  the number of days to obtain an instance for
077     * @return the instance of Days
078     */
079    public static Days days(int days) {
080        switch (days) {
081            case 0:
082                return ZERO;
083            case 1:
084                return ONE;
085            case 2:
086                return TWO;
087            case 3:
088                return THREE;
089            case 4:
090                return FOUR;
091            case 5:
092                return FIVE;
093            case 6:
094                return SIX;
095            case 7:
096                return SEVEN;
097            case Integer.MAX_VALUE:
098                return MAX_VALUE;
099            case Integer.MIN_VALUE:
100                return MIN_VALUE;
101            default:
102                return new Days(days);
103        }
104    }
105
106    //-----------------------------------------------------------------------
107    /**
108     * Creates a <code>Days</code> representing the number of whole days
109     * between the two specified datetimes. This method corectly handles
110     * any daylight savings time changes that may occur during the interval.
111     *
112     * @param start  the start instant, must not be null
113     * @param end  the end instant, must not be null
114     * @return the period in days
115     * @throws IllegalArgumentException if the instants are null or invalid
116     */
117    public static Days daysBetween(ReadableInstant start, ReadableInstant end) {
118        int amount = BaseSingleFieldPeriod.between(start, end, DurationFieldType.days());
119        return Days.days(amount);
120    }
121
122    /**
123     * Creates a <code>Days</code> representing the number of whole days
124     * between the two specified partial datetimes.
125     * <p>
126     * The two partials must contain the same fields, for example you can specify
127     * two <code>LocalDate</code> objects.
128     *
129     * @param start  the start partial date, must not be null
130     * @param end  the end partial date, must not be null
131     * @return the period in days
132     * @throws IllegalArgumentException if the partials are null or invalid
133     */
134    public static Days daysBetween(ReadablePartial start, ReadablePartial end) {
135        if (start instanceof LocalDate && end instanceof LocalDate)   {
136            Chronology chrono = DateTimeUtils.getChronology(start.getChronology());
137            int days = chrono.days().getDifference(
138                    ((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis());
139            return Days.days(days);
140        }
141        int amount = BaseSingleFieldPeriod.between(start, end, ZERO);
142        return Days.days(amount);
143    }
144
145    /**
146     * Creates a <code>Days</code> representing the number of whole days
147     * in the specified interval. This method corectly handles any daylight
148     * savings time changes that may occur during the interval.
149     *
150     * @param interval  the interval to extract days from, null returns zero
151     * @return the period in days
152     * @throws IllegalArgumentException if the partials are null or invalid
153     */
154    public static Days daysIn(ReadableInterval interval) {
155        if (interval == null)   {
156            return Days.ZERO;
157        }
158        int amount = BaseSingleFieldPeriod.between(interval.getStart(), interval.getEnd(), DurationFieldType.days());
159        return Days.days(amount);
160    }
161
162    /**
163     * Creates a new <code>Days</code> representing the number of complete
164     * standard length days in the specified period.
165     * <p>
166     * This factory method converts all fields from the period to hours using standardised
167     * durations for each field. Only those fields which have a precise duration in
168     * the ISO UTC chronology can be converted.
169     * <ul>
170     * <li>One week consists of 7 days.
171     * <li>One day consists of 24 hours.
172     * <li>One hour consists of 60 minutes.
173     * <li>One minute consists of 60 seconds.
174     * <li>One second consists of 1000 milliseconds.
175     * </ul>
176     * Months and Years are imprecise and periods containing these values cannot be converted.
177     *
178     * @param period  the period to get the number of hours from, null returns zero
179     * @return the period in days
180     * @throws IllegalArgumentException if the period contains imprecise duration values
181     */
182    public static Days standardDaysIn(ReadablePeriod period) {
183        int amount = BaseSingleFieldPeriod.standardPeriodIn(period, DateTimeConstants.MILLIS_PER_DAY);
184        return Days.days(amount);
185    }
186
187    /**
188     * Creates a new <code>Days</code> by parsing a string in the ISO8601 format 'PnD'.
189     * <p>
190     * The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the
191     * days component may be non-zero. If any other component is non-zero, an exception
192     * will be thrown.
193     *
194     * @param periodStr  the period string, null returns zero
195     * @return the period in days
196     * @throws IllegalArgumentException if the string format is invalid
197     */
198    @FromString
199    public static Days parseDays(String periodStr) {
200        if (periodStr == null) {
201            return Days.ZERO;
202        }
203        Period p = PARSER.parsePeriod(periodStr);
204        return Days.days(p.getDays());
205    }
206
207    //-----------------------------------------------------------------------
208    /**
209     * Creates a new instance representing a number of days.
210     * You should consider using the factory method {@link #days(int)}
211     * instead of the constructor.
212     *
213     * @param days  the number of days to represent
214     */
215    private Days(int days) {
216        super(days);
217    }
218
219    /**
220     * Resolves singletons.
221     * 
222     * @return the singleton instance
223     */
224    private Object readResolve() {
225        return Days.days(getValue());
226    }
227
228    //-----------------------------------------------------------------------
229    /**
230     * Gets the duration field type, which is <code>days</code>.
231     *
232     * @return the period type
233     */
234    public DurationFieldType getFieldType() {
235        return DurationFieldType.days();
236    }
237
238    /**
239     * Gets the period type, which is <code>days</code>.
240     *
241     * @return the period type
242     */
243    public PeriodType getPeriodType() {
244        return PeriodType.days();
245    }
246
247    //-----------------------------------------------------------------------
248    /**
249     * Converts this period in days to a period in weeks assuming a
250     * 7 day week.
251     * <p>
252     * This method allows you to convert between different types of period.
253     * However to achieve this it makes the assumption that all weeks are
254     * 7 days long.
255     * This may not be true for some unusual chronologies. However, it is included
256     * as it is a useful operation for many applications and business rules.
257     * 
258     * @return a period representing the number of weeks for this number of days
259     */
260    public Weeks toStandardWeeks() {
261        return Weeks.weeks(getValue() / DateTimeConstants.DAYS_PER_WEEK);
262    }
263
264    /**
265     * Converts this period in days to a period in hours assuming a
266     * 24 hour day.
267     * <p>
268     * This method allows you to convert between different types of period.
269     * However to achieve this it makes the assumption that all days are 24 hours long.
270     * This is not true when daylight savings is considered and may also not
271     * be true for some unusual chronologies. However, it is included
272     * as it is a useful operation for many applications and business rules.
273     * 
274     * @return a period representing the number of hours for this number of days
275     * @throws ArithmeticException if the number of hours is too large to be represented
276     */
277    public Hours toStandardHours() {
278        return Hours.hours(FieldUtils.safeMultiply(getValue(), DateTimeConstants.HOURS_PER_DAY));
279    }
280
281    /**
282     * Converts this period in days to a period in minutes assuming a
283     * 24 hour day and 60 minute hour.
284     * <p>
285     * This method allows you to convert between different types of period.
286     * However to achieve this it makes the assumption that all days are 24 hours
287     * long and all hours are 60 minutes long.
288     * This is not true when daylight savings is considered and may also not
289     * be true for some unusual chronologies. However, it is included
290     * as it is a useful operation for many applications and business rules.
291     * 
292     * @return a period representing the number of minutes for this number of days
293     * @throws ArithmeticException if the number of minutes is too large to be represented
294     */
295    public Minutes toStandardMinutes() {
296        return Minutes.minutes(FieldUtils.safeMultiply(getValue(), DateTimeConstants.MINUTES_PER_DAY));
297    }
298
299    /**
300     * Converts this period in days to a period in seconds assuming a
301     * 24 hour day, 60 minute hour and 60 second minute.
302     * <p>
303     * This method allows you to convert between different types of period.
304     * However to achieve this it makes the assumption that all days are 24 hours
305     * long, all hours are 60 minutes long and all minutes are 60 seconds long.
306     * This is not true when daylight savings is considered and may also not
307     * be true for some unusual chronologies. However, it is included
308     * as it is a useful operation for many applications and business rules.
309     * 
310     * @return a period representing the number of seconds for this number of days
311     * @throws ArithmeticException if the number of seconds is too large to be represented
312     */
313    public Seconds toStandardSeconds() {
314        return Seconds.seconds(FieldUtils.safeMultiply(getValue(), DateTimeConstants.SECONDS_PER_DAY));
315    }
316
317    //-----------------------------------------------------------------------
318    /**
319     * Converts this period in days to a duration in milliseconds assuming a
320     * 24 hour day, 60 minute hour and 60 second minute.
321     * <p>
322     * This method allows you to convert from a period to a duration.
323     * However to achieve this it makes the assumption that all days are 24 hours
324     * long, all hours are 60 minutes and all minutes are 60 seconds.
325     * This is not true when daylight savings time is considered, and may also
326     * not be true for some unusual chronologies. However, it is included as it
327     * is a useful operation for many applications and business rules.
328     * 
329     * @return a duration equivalent to this number of days
330     */
331    public Duration toStandardDuration() {
332        long days = getValue();  // assign to a long
333        return new Duration(days * DateTimeConstants.MILLIS_PER_DAY);
334    }
335
336    //-----------------------------------------------------------------------
337    /**
338     * Gets the number of days that this period represents.
339     *
340     * @return the number of days in the period
341     */
342    public int getDays() {
343        return getValue();
344    }
345
346    //-----------------------------------------------------------------------
347    /**
348     * Returns a new instance with the specified number of days added.
349     * <p>
350     * This instance is immutable and unaffected by this method call.
351     *
352     * @param days  the amount of days to add, may be negative
353     * @return the new period plus the specified number of days
354     * @throws ArithmeticException if the result overflows an int
355     */
356    public Days plus(int days) {
357        if (days == 0) {
358            return this;
359        }
360        return Days.days(FieldUtils.safeAdd(getValue(), days));
361    }
362
363    /**
364     * Returns a new instance with the specified number of days added.
365     * <p>
366     * This instance is immutable and unaffected by this method call.
367     *
368     * @param days  the amount of days to add, may be negative, null means zero
369     * @return the new period plus the specified number of days
370     * @throws ArithmeticException if the result overflows an int
371     */
372    public Days plus(Days days) {
373        if (days == null) {
374            return this;
375        }
376        return plus(days.getValue());
377    }
378
379    //-----------------------------------------------------------------------
380    /**
381     * Returns a new instance with the specified number of days taken away.
382     * <p>
383     * This instance is immutable and unaffected by this method call.
384     *
385     * @param days  the amount of days to take away, may be negative
386     * @return the new period minus the specified number of days
387     * @throws ArithmeticException if the result overflows an int
388     */
389    public Days minus(int days) {
390        return plus(FieldUtils.safeNegate(days));
391    }
392
393    /**
394     * Returns a new instance with the specified number of days taken away.
395     * <p>
396     * This instance is immutable and unaffected by this method call.
397     *
398     * @param days  the amount of days to take away, may be negative, null means zero
399     * @return the new period minus the specified number of days
400     * @throws ArithmeticException if the result overflows an int
401     */
402    public Days minus(Days days) {
403        if (days == null) {
404            return this;
405        }
406        return minus(days.getValue());
407    }
408
409    //-----------------------------------------------------------------------
410    /**
411     * Returns a new instance with the days multiplied by the specified scalar.
412     * <p>
413     * This instance is immutable and unaffected by this method call.
414     *
415     * @param scalar  the amount to multiply by, may be negative
416     * @return the new period multiplied by the specified scalar
417     * @throws ArithmeticException if the result overflows an int
418     */
419    public Days multipliedBy(int scalar) {
420        return Days.days(FieldUtils.safeMultiply(getValue(), scalar));
421    }
422
423    /**
424     * Returns a new instance with the days divided by the specified divisor.
425     * The calculation uses integer division, thus 3 divided by 2 is 1.
426     * <p>
427     * This instance is immutable and unaffected by this method call.
428     *
429     * @param divisor  the amount to divide by, may be negative
430     * @return the new period divided by the specified divisor
431     * @throws ArithmeticException if the divisor is zero
432     */
433    public Days dividedBy(int divisor) {
434        if (divisor == 1) {
435            return this;
436        }
437        return Days.days(getValue() / divisor);
438    }
439
440    //-----------------------------------------------------------------------
441    /**
442     * Returns a new instance with the days value negated.
443     *
444     * @return the new period with a negated value
445     * @throws ArithmeticException if the result overflows an int
446     */
447    public Days negated() {
448        return Days.days(FieldUtils.safeNegate(getValue()));
449    }
450
451    //-----------------------------------------------------------------------
452    /**
453     * Is this days instance greater than the specified number of days.
454     *
455     * @param other  the other period, null means zero
456     * @return true if this days instance is greater than the specified one
457     */
458    public boolean isGreaterThan(Days other) {
459        if (other == null) {
460            return getValue() > 0;
461        }
462        return getValue() > other.getValue();
463    }
464
465    /**
466     * Is this days instance less than the specified number of days.
467     *
468     * @param other  the other period, null means zero
469     * @return true if this days instance is less than the specified one
470     */
471    public boolean isLessThan(Days other) {
472        if (other == null) {
473            return getValue() < 0;
474        }
475        return getValue() < other.getValue();
476    }
477
478    //-----------------------------------------------------------------------
479    /**
480     * Gets this instance as a String in the ISO8601 duration format.
481     * <p>
482     * For example, "P4D" represents 4 days.
483     *
484     * @return the value as an ISO8601 string
485     */
486    @ToString
487    public String toString() {
488        return "P" + String.valueOf(getValue()) + "D";
489    }
490
491}