001/*
002 *  Copyright 2001-2006 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.time.base.BaseSingleFieldPeriod;
019import org.joda.time.field.FieldUtils;
020import org.joda.time.format.ISOPeriodFormat;
021import org.joda.time.format.PeriodFormatter;
022
023/**
024 * An immutable time period representing a number of days.
025 * <p>
026 * <code>Days</code> is an immutable period that can only store days.
027 * It does not store years, months or hours for example. As such it is a
028 * type-safe way of representing a number of days in an application.
029 * <p>
030 * The number of days is set in the constructor, and may be queried using
031 * <code>getDays()</code>. Basic mathematical operations are provided -
032 * <code>plus()</code>, <code>minus()</code>, <code>multipliedBy()</code> and
033 * <code>dividedBy()</code>.
034 * <p>
035 * <code>Days</code> is thread-safe and immutable.
036 *
037 * @author Stephen Colebourne
038 * @since 1.4
039 */
040public final class Days extends BaseSingleFieldPeriod {
041
042    /** Constant representing zero days. */
043    public static final Days ZERO = new Days(0);
044    /** Constant representing one day. */
045    public static final Days ONE = new Days(1);
046    /** Constant representing two days. */
047    public static final Days TWO = new Days(2);
048    /** Constant representing three days. */
049    public static final Days THREE = new Days(3);
050    /** Constant representing four days. */
051    public static final Days FOUR = new Days(4);
052    /** Constant representing five days. */
053    public static final Days FIVE = new Days(5);
054    /** Constant representing six days. */
055    public static final Days SIX = new Days(6);
056    /** Constant representing seven days. */
057    public static final Days SEVEN = new Days(7);
058    /** Constant representing the maximum number of days that can be stored in this object. */
059    public static final Days MAX_VALUE = new Days(Integer.MAX_VALUE);
060    /** Constant representing the minimum number of days that can be stored in this object. */
061    public static final Days MIN_VALUE = new Days(Integer.MIN_VALUE);
062
063    /** The paser to use for this class. */
064    private static final PeriodFormatter PARSER = ISOPeriodFormat.standard().withParseType(PeriodType.days());
065    /** Serialization version. */
066    private static final long serialVersionUID = 87525275727380865L;
067
068    //-----------------------------------------------------------------------
069    /**
070     * Obtains an instance of <code>Days</code> that may be cached.
071     * <code>Days</code> is immutable, so instances can be cached and shared.
072     * This factory method provides access to shared instances.
073     *
074     * @param days  the number of days to obtain an instance for
075     * @return the instance of Days
076     */
077    public static Days days(int days) {
078        switch (days) {
079            case 0:
080                return ZERO;
081            case 1:
082                return ONE;
083            case 2:
084                return TWO;
085            case 3:
086                return THREE;
087            case 4:
088                return FOUR;
089            case 5:
090                return FIVE;
091            case 6:
092                return SIX;
093            case 7:
094                return SEVEN;
095            case Integer.MAX_VALUE:
096                return MAX_VALUE;
097            case Integer.MIN_VALUE:
098                return MIN_VALUE;
099            default:
100                return new Days(days);
101        }
102    }
103
104    //-----------------------------------------------------------------------
105    /**
106     * Creates a <code>Days</code> representing the number of whole days
107     * between the two specified datetimes. This method corectly handles
108     * any daylight savings time changes that may occur during the interval.
109     *
110     * @param start  the start instant, must not be null
111     * @param end  the end instant, must not be null
112     * @return the period in days
113     * @throws IllegalArgumentException if the instants are null or invalid
114     */
115    public static Days daysBetween(ReadableInstant start, ReadableInstant end) {
116        int amount = BaseSingleFieldPeriod.between(start, end, DurationFieldType.days());
117        return Days.days(amount);
118    }
119
120    /**
121     * Creates a <code>Days</code> representing the number of whole days
122     * between the two specified partial datetimes.
123     * <p>
124     * The two partials must contain the same fields, for example you can specify
125     * two <code>LocalDate</code> objects.
126     *
127     * @param start  the start partial date, must not be null
128     * @param end  the end partial date, must not be null
129     * @return the period in days
130     * @throws IllegalArgumentException if the partials are null or invalid
131     */
132    public static Days daysBetween(ReadablePartial start, ReadablePartial end) {
133        if (start instanceof LocalDate && end instanceof LocalDate)   {
134            Chronology chrono = DateTimeUtils.getChronology(start.getChronology());
135            int days = chrono.days().getDifference(
136                    ((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis());
137            return Days.days(days);
138        }
139        int amount = BaseSingleFieldPeriod.between(start, end, ZERO);
140        return Days.days(amount);
141    }
142
143    /**
144     * Creates a <code>Days</code> representing the number of whole days
145     * in the specified interval. This method corectly handles any daylight
146     * savings time changes that may occur during the interval.
147     *
148     * @param interval  the interval to extract days from, null returns zero
149     * @return the period in days
150     * @throws IllegalArgumentException if the partials are null or invalid
151     */
152    public static Days daysIn(ReadableInterval interval) {
153        if (interval == null)   {
154            return Days.ZERO;
155        }
156        int amount = BaseSingleFieldPeriod.between(interval.getStart(), interval.getEnd(), DurationFieldType.days());
157        return Days.days(amount);
158    }
159
160    /**
161     * Creates a new <code>Days</code> representing the number of complete
162     * standard length days in the specified period.
163     * <p>
164     * This factory method converts all fields from the period to hours using standardised
165     * durations for each field. Only those fields which have a precise duration in
166     * the ISO UTC chronology can be converted.
167     * <ul>
168     * <li>One week consists of 7 days.
169     * <li>One day consists of 24 hours.
170     * <li>One hour consists of 60 minutes.
171     * <li>One minute consists of 60 seconds.
172     * <li>One second consists of 1000 milliseconds.
173     * </ul>
174     * Months and Years are imprecise and periods containing these values cannot be converted.
175     *
176     * @param period  the period to get the number of hours from, null returns zero
177     * @return the period in days
178     * @throws IllegalArgumentException if the period contains imprecise duration values
179     */
180    public static Days standardDaysIn(ReadablePeriod period) {
181        int amount = BaseSingleFieldPeriod.standardPeriodIn(period, DateTimeConstants.MILLIS_PER_DAY);
182        return Days.days(amount);
183    }
184
185    /**
186     * Creates a new <code>Days</code> by parsing a string in the ISO8601 format 'PnD'.
187     * <p>
188     * The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the
189     * days component may be non-zero. If any other component is non-zero, an exception
190     * will be thrown.
191     *
192     * @param periodStr  the period string, null returns zero
193     * @return the period in days
194     * @throws IllegalArgumentException if the string format is invalid
195     */
196    public static Days parseDays(String periodStr) {
197        if (periodStr == null) {
198            return Days.ZERO;
199        }
200        Period p = PARSER.parsePeriod(periodStr);
201        return Days.days(p.getDays());
202    }
203
204    //-----------------------------------------------------------------------
205    /**
206     * Creates a new instance representing a number of days.
207     * You should consider using the factory method {@link #days(int)}
208     * instead of the constructor.
209     *
210     * @param days  the number of days to represent
211     */
212    private Days(int days) {
213        super(days);
214    }
215
216    /**
217     * Resolves singletons.
218     * 
219     * @return the singleton instance
220     */
221    private Object readResolve() {
222        return Days.days(getValue());
223    }
224
225    //-----------------------------------------------------------------------
226    /**
227     * Gets the duration field type, which is <code>days</code>.
228     *
229     * @return the period type
230     */
231    public DurationFieldType getFieldType() {
232        return DurationFieldType.days();
233    }
234
235    /**
236     * Gets the period type, which is <code>days</code>.
237     *
238     * @return the period type
239     */
240    public PeriodType getPeriodType() {
241        return PeriodType.days();
242    }
243
244    //-----------------------------------------------------------------------
245    /**
246     * Converts this period in days to a period in weeks assuming a
247     * 7 day week.
248     * <p>
249     * This method allows you to convert between different types of period.
250     * However to achieve this it makes the assumption that all weeks are
251     * 7 days long.
252     * This may not be true for some unusual chronologies. However, it is included
253     * as it is a useful operation for many applications and business rules.
254     * 
255     * @return a period representing the number of weeks for this number of days
256     */
257    public Weeks toStandardWeeks() {
258        return Weeks.weeks(getValue() / DateTimeConstants.DAYS_PER_WEEK);
259    }
260
261    /**
262     * Converts this period in days to a period in hours assuming a
263     * 24 hour day.
264     * <p>
265     * This method allows you to convert between different types of period.
266     * However to achieve this it makes the assumption that all days are 24 hours long.
267     * This is not true when daylight savings is considered and may also not
268     * be true for some unusual chronologies. However, it is included
269     * as it is a useful operation for many applications and business rules.
270     * 
271     * @return a period representing the number of hours for this number of days
272     * @throws ArithmeticException if the number of hours is too large to be represented
273     */
274    public Hours toStandardHours() {
275        return Hours.hours(FieldUtils.safeMultiply(getValue(), DateTimeConstants.HOURS_PER_DAY));
276    }
277
278    /**
279     * Converts this period in days to a period in minutes assuming a
280     * 24 hour day and 60 minute hour.
281     * <p>
282     * This method allows you to convert between different types of period.
283     * However to achieve this it makes the assumption that all days are 24 hours
284     * long and all hours are 60 minutes long.
285     * This is not true when daylight savings is considered and may also not
286     * be true for some unusual chronologies. However, it is included
287     * as it is a useful operation for many applications and business rules.
288     * 
289     * @return a period representing the number of minutes for this number of days
290     * @throws ArithmeticException if the number of minutes is too large to be represented
291     */
292    public Minutes toStandardMinutes() {
293        return Minutes.minutes(FieldUtils.safeMultiply(getValue(), DateTimeConstants.MINUTES_PER_DAY));
294    }
295
296    /**
297     * Converts this period in days to a period in seconds assuming a
298     * 24 hour day, 60 minute hour and 60 second minute.
299     * <p>
300     * This method allows you to convert between different types of period.
301     * However to achieve this it makes the assumption that all days are 24 hours
302     * long, all hours are 60 minutes long and all minutes are 60 seconds long.
303     * This is not true when daylight savings is considered and may also not
304     * be true for some unusual chronologies. However, it is included
305     * as it is a useful operation for many applications and business rules.
306     * 
307     * @return a period representing the number of seconds for this number of days
308     * @throws ArithmeticException if the number of seconds is too large to be represented
309     */
310    public Seconds toStandardSeconds() {
311        return Seconds.seconds(FieldUtils.safeMultiply(getValue(), DateTimeConstants.SECONDS_PER_DAY));
312    }
313
314    //-----------------------------------------------------------------------
315    /**
316     * Converts this period in days to a duration in milliseconds assuming a
317     * 24 hour day, 60 minute hour and 60 second minute.
318     * <p>
319     * This method allows you to convert from a period to a duration.
320     * However to achieve this it makes the assumption that all days are 24 hours
321     * long, all hours are 60 minutes and all minutes are 60 seconds.
322     * This is not true when daylight savings time is considered, and may also
323     * not be true for some unusual chronologies. However, it is included as it
324     * is a useful operation for many applications and business rules.
325     * 
326     * @return a duration equivalent to this number of days
327     */
328    public Duration toStandardDuration() {
329        long days = getValue();  // assign to a long
330        return new Duration(days * DateTimeConstants.MILLIS_PER_DAY);
331    }
332
333    //-----------------------------------------------------------------------
334    /**
335     * Gets the number of days that this period represents.
336     *
337     * @return the number of days in the period
338     */
339    public int getDays() {
340        return getValue();
341    }
342
343    //-----------------------------------------------------------------------
344    /**
345     * Returns a new instance with the specified number of days added.
346     * <p>
347     * This instance is immutable and unaffected by this method call.
348     *
349     * @param days  the amount of days to add, may be negative
350     * @return the new period plus the specified number of days
351     * @throws ArithmeticException if the result overflows an int
352     */
353    public Days plus(int days) {
354        if (days == 0) {
355            return this;
356        }
357        return Days.days(FieldUtils.safeAdd(getValue(), days));
358    }
359
360    /**
361     * Returns a new instance with the specified number of days added.
362     * <p>
363     * This instance is immutable and unaffected by this method call.
364     *
365     * @param days  the amount of days to add, may be negative, null means zero
366     * @return the new period plus the specified number of days
367     * @throws ArithmeticException if the result overflows an int
368     */
369    public Days plus(Days days) {
370        if (days == null) {
371            return this;
372        }
373        return plus(days.getValue());
374    }
375
376    //-----------------------------------------------------------------------
377    /**
378     * Returns a new instance with the specified number of days taken away.
379     * <p>
380     * This instance is immutable and unaffected by this method call.
381     *
382     * @param days  the amount of days to take away, may be negative
383     * @return the new period minus the specified number of days
384     * @throws ArithmeticException if the result overflows an int
385     */
386    public Days minus(int days) {
387        return plus(FieldUtils.safeNegate(days));
388    }
389
390    /**
391     * Returns a new instance with the specified number of days taken away.
392     * <p>
393     * This instance is immutable and unaffected by this method call.
394     *
395     * @param days  the amount of days to take away, may be negative, null means zero
396     * @return the new period minus the specified number of days
397     * @throws ArithmeticException if the result overflows an int
398     */
399    public Days minus(Days days) {
400        if (days == null) {
401            return this;
402        }
403        return minus(days.getValue());
404    }
405
406    //-----------------------------------------------------------------------
407    /**
408     * Returns a new instance with the days multiplied by the specified scalar.
409     * <p>
410     * This instance is immutable and unaffected by this method call.
411     *
412     * @param scalar  the amount to multiply by, may be negative
413     * @return the new period multiplied by the specified scalar
414     * @throws ArithmeticException if the result overflows an int
415     */
416    public Days multipliedBy(int scalar) {
417        return Days.days(FieldUtils.safeMultiply(getValue(), scalar));
418    }
419
420    /**
421     * Returns a new instance with the days divided by the specified divisor.
422     * The calculation uses integer division, thus 3 divided by 2 is 1.
423     * <p>
424     * This instance is immutable and unaffected by this method call.
425     *
426     * @param divisor  the amount to divide by, may be negative
427     * @return the new period divided by the specified divisor
428     * @throws ArithmeticException if the divisor is zero
429     */
430    public Days dividedBy(int divisor) {
431        if (divisor == 1) {
432            return this;
433        }
434        return Days.days(getValue() / divisor);
435    }
436
437    //-----------------------------------------------------------------------
438    /**
439     * Returns a new instance with the days value negated.
440     *
441     * @return the new period with a negated value
442     * @throws ArithmeticException if the result overflows an int
443     */
444    public Days negated() {
445        return Days.days(FieldUtils.safeNegate(getValue()));
446    }
447
448    //-----------------------------------------------------------------------
449    /**
450     * Is this days instance greater than the specified number of days.
451     *
452     * @param other  the other period, null means zero
453     * @return true if this days instance is greater than the specified one
454     */
455    public boolean isGreaterThan(Days other) {
456        if (other == null) {
457            return getValue() > 0;
458        }
459        return getValue() > other.getValue();
460    }
461
462    /**
463     * Is this days instance less than the specified number of days.
464     *
465     * @param other  the other period, null means zero
466     * @return true if this days instance is less than the specified one
467     */
468    public boolean isLessThan(Days other) {
469        if (other == null) {
470            return getValue() < 0;
471        }
472        return getValue() < other.getValue();
473    }
474
475    //-----------------------------------------------------------------------
476    /**
477     * Gets this instance as a String in the ISO8601 duration format.
478     * <p>
479     * For example, "P4D" represents 4 days.
480     *
481     * @return the value as an ISO8601 string
482     */
483    public String toString() {
484        return "P" + String.valueOf(getValue()) + "D";
485    }
486
487}