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26 /*
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62 package java.time;
63 
64 import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
65 import static java.time.temporal.ChronoUnit.MONTHS;
66 
67 import java.time.chrono.Chronology;
68 import java.time.chrono.IsoChronology;
69 import java.time.format.DateTimeFormatterBuilder;
70 import java.time.format.TextStyle;
71 import java.time.temporal.ChronoField;
72 import java.time.temporal.Temporal;
73 import java.time.temporal.TemporalAccessor;
74 import java.time.temporal.TemporalAdjuster;
75 import java.time.temporal.TemporalField;
76 import java.time.temporal.TemporalQueries;
77 import java.time.temporal.TemporalQuery;
78 import java.time.temporal.UnsupportedTemporalTypeException;
79 import java.time.temporal.ValueRange;
80 import java.util.Locale;
81 
82 /**
83  * A month-of-year, such as 'July'.
84  * <p>
85  * {@code Month} is an enum representing the 12 months of the year -
86  * January, February, March, April, May, June, July, August, September, October,
87  * November and December.
88  * <p>
89  * In addition to the textual enum name, each month-of-year has an {@code int} value.
90  * The {@code int} value follows normal usage and the ISO-8601 standard,
91  * from 1 (January) to 12 (December). It is recommended that applications use the enum
92  * rather than the {@code int} value to ensure code clarity.
93  * <p>
94  * <b>Do not use {@code ordinal()} to obtain the numeric representation of {@code Month}.
95  * Use {@code getValue()} instead.</b>
96  * <p>
97  * This enum represents a common concept that is found in many calendar systems.
98  * As such, this enum may be used by any calendar system that has the month-of-year
99  * concept defined exactly equivalent to the ISO-8601 calendar system.
100  *
101  * @implSpec
102  * This is an immutable and thread-safe enum.
103  *
104  * @since 1.8
105  */
106 public enum Month implements TemporalAccessor, TemporalAdjuster {
107 
108     /**
109      * The singleton instance for the month of January with 31 days.
110      * This has the numeric value of {@code 1}.
111      */
112     JANUARY,
113     /**
114      * The singleton instance for the month of February with 28 days, or 29 in a leap year.
115      * This has the numeric value of {@code 2}.
116      */
117     FEBRUARY,
118     /**
119      * The singleton instance for the month of March with 31 days.
120      * This has the numeric value of {@code 3}.
121      */
122     MARCH,
123     /**
124      * The singleton instance for the month of April with 30 days.
125      * This has the numeric value of {@code 4}.
126      */
127     APRIL,
128     /**
129      * The singleton instance for the month of May with 31 days.
130      * This has the numeric value of {@code 5}.
131      */
132     MAY,
133     /**
134      * The singleton instance for the month of June with 30 days.
135      * This has the numeric value of {@code 6}.
136      */
137     JUNE,
138     /**
139      * The singleton instance for the month of July with 31 days.
140      * This has the numeric value of {@code 7}.
141      */
142     JULY,
143     /**
144      * The singleton instance for the month of August with 31 days.
145      * This has the numeric value of {@code 8}.
146      */
147     AUGUST,
148     /**
149      * The singleton instance for the month of September with 30 days.
150      * This has the numeric value of {@code 9}.
151      */
152     SEPTEMBER,
153     /**
154      * The singleton instance for the month of October with 31 days.
155      * This has the numeric value of {@code 10}.
156      */
157     OCTOBER,
158     /**
159      * The singleton instance for the month of November with 30 days.
160      * This has the numeric value of {@code 11}.
161      */
162     NOVEMBER,
163     /**
164      * The singleton instance for the month of December with 31 days.
165      * This has the numeric value of {@code 12}.
166      */
167     DECEMBER;
168     /**
169      * Private cache of all the constants.
170      */
171     private static final Month[] ENUMS = Month.values();
172 
173     //-----------------------------------------------------------------------
174     /**
175      * Obtains an instance of {@code Month} from an {@code int} value.
176      * <p>
177      * {@code Month} is an enum representing the 12 months of the year.
178      * This factory allows the enum to be obtained from the {@code int} value.
179      * The {@code int} value follows the ISO-8601 standard, from 1 (January) to 12 (December).
180      *
181      * @param month  the month-of-year to represent, from 1 (January) to 12 (December)
182      * @return the month-of-year, not null
183      * @throws DateTimeException if the month-of-year is invalid
184      */
of(int month)185     public static Month of(int month) {
186         if (month < 1 || month > 12) {
187             throw new DateTimeException("Invalid value for MonthOfYear: " + month);
188         }
189         return ENUMS[month - 1];
190     }
191 
192     //-----------------------------------------------------------------------
193     /**
194      * Obtains an instance of {@code Month} from a temporal object.
195      * <p>
196      * This obtains a month based on the specified temporal.
197      * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
198      * which this factory converts to an instance of {@code Month}.
199      * <p>
200      * The conversion extracts the {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} field.
201      * The extraction is only permitted if the temporal object has an ISO
202      * chronology, or can be converted to a {@code LocalDate}.
203      * <p>
204      * This method matches the signature of the functional interface {@link TemporalQuery}
205      * allowing it to be used as a query via method reference, {@code Month::from}.
206      *
207      * @param temporal  the temporal object to convert, not null
208      * @return the month-of-year, not null
209      * @throws DateTimeException if unable to convert to a {@code Month}
210      */
from(TemporalAccessor temporal)211     public static Month from(TemporalAccessor temporal) {
212         if (temporal instanceof Month) {
213             return (Month) temporal;
214         }
215         try {
216             if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) {
217                 temporal = LocalDate.from(temporal);
218             }
219             return of(temporal.get(MONTH_OF_YEAR));
220         } catch (DateTimeException ex) {
221             throw new DateTimeException("Unable to obtain Month from TemporalAccessor: " +
222                     temporal + " of type " + temporal.getClass().getName(), ex);
223         }
224     }
225 
226     //-----------------------------------------------------------------------
227     /**
228      * Gets the month-of-year {@code int} value.
229      * <p>
230      * The values are numbered following the ISO-8601 standard,
231      * from 1 (January) to 12 (December).
232      *
233      * @return the month-of-year, from 1 (January) to 12 (December)
234      */
getValue()235     public int getValue() {
236         return ordinal() + 1;
237     }
238 
239     //-----------------------------------------------------------------------
240     /**
241      * Gets the textual representation, such as 'Jan' or 'December'.
242      * <p>
243      * This returns the textual name used to identify the month-of-year,
244      * suitable for presentation to the user.
245      * The parameters control the style of the returned text and the locale.
246      * <p>
247      * If no textual mapping is found then the {@link #getValue() numeric value} is returned.
248      *
249      * @param style  the length of the text required, not null
250      * @param locale  the locale to use, not null
251      * @return the text value of the month-of-year, not null
252      */
getDisplayName(TextStyle style, Locale locale)253     public String getDisplayName(TextStyle style, Locale locale) {
254         return new DateTimeFormatterBuilder().appendText(MONTH_OF_YEAR, style).toFormatter(locale).format(this);
255     }
256 
257     //-----------------------------------------------------------------------
258     /**
259      * Checks if the specified field is supported.
260      * <p>
261      * This checks if this month-of-year can be queried for the specified field.
262      * If false, then calling the {@link #range(TemporalField) range} and
263      * {@link #get(TemporalField) get} methods will throw an exception.
264      * <p>
265      * If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then
266      * this method returns true.
267      * All other {@code ChronoField} instances will return false.
268      * <p>
269      * If the field is not a {@code ChronoField}, then the result of this method
270      * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
271      * passing {@code this} as the argument.
272      * Whether the field is supported is determined by the field.
273      *
274      * @param field  the field to check, null returns false
275      * @return true if the field is supported on this month-of-year, false if not
276      */
277     @Override
isSupported(TemporalField field)278     public boolean isSupported(TemporalField field) {
279         if (field instanceof ChronoField) {
280             return field == MONTH_OF_YEAR;
281         }
282         return field != null && field.isSupportedBy(this);
283     }
284 
285     /**
286      * Gets the range of valid values for the specified field.
287      * <p>
288      * The range object expresses the minimum and maximum valid values for a field.
289      * This month is used to enhance the accuracy of the returned range.
290      * If it is not possible to return the range, because the field is not supported
291      * or for some other reason, an exception is thrown.
292      * <p>
293      * If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the
294      * range of the month-of-year, from 1 to 12, will be returned.
295      * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
296      * <p>
297      * If the field is not a {@code ChronoField}, then the result of this method
298      * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
299      * passing {@code this} as the argument.
300      * Whether the range can be obtained is determined by the field.
301      *
302      * @param field  the field to query the range for, not null
303      * @return the range of valid values for the field, not null
304      * @throws DateTimeException if the range for the field cannot be obtained
305      * @throws UnsupportedTemporalTypeException if the field is not supported
306      */
307     @Override
range(TemporalField field)308     public ValueRange range(TemporalField field) {
309         if (field == MONTH_OF_YEAR) {
310             return field.range();
311         }
312         return TemporalAccessor.super.range(field);
313     }
314 
315     /**
316      * Gets the value of the specified field from this month-of-year as an {@code int}.
317      * <p>
318      * This queries this month for the value of the specified field.
319      * The returned value will always be within the valid range of values for the field.
320      * If it is not possible to return the value, because the field is not supported
321      * or for some other reason, an exception is thrown.
322      * <p>
323      * If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the
324      * value of the month-of-year, from 1 to 12, will be returned.
325      * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
326      * <p>
327      * If the field is not a {@code ChronoField}, then the result of this method
328      * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
329      * passing {@code this} as the argument. Whether the value can be obtained,
330      * and what the value represents, is determined by the field.
331      *
332      * @param field  the field to get, not null
333      * @return the value for the field, within the valid range of values
334      * @throws DateTimeException if a value for the field cannot be obtained or
335      *         the value is outside the range of valid values for the field
336      * @throws UnsupportedTemporalTypeException if the field is not supported or
337      *         the range of values exceeds an {@code int}
338      * @throws ArithmeticException if numeric overflow occurs
339      */
340     @Override
get(TemporalField field)341     public int get(TemporalField field) {
342         if (field == MONTH_OF_YEAR) {
343             return getValue();
344         }
345         return TemporalAccessor.super.get(field);
346     }
347 
348     /**
349      * Gets the value of the specified field from this month-of-year as a {@code long}.
350      * <p>
351      * This queries this month for the value of the specified field.
352      * If it is not possible to return the value, because the field is not supported
353      * or for some other reason, an exception is thrown.
354      * <p>
355      * If the field is {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} then the
356      * value of the month-of-year, from 1 to 12, will be returned.
357      * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
358      * <p>
359      * If the field is not a {@code ChronoField}, then the result of this method
360      * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
361      * passing {@code this} as the argument. Whether the value can be obtained,
362      * and what the value represents, is determined by the field.
363      *
364      * @param field  the field to get, not null
365      * @return the value for the field
366      * @throws DateTimeException if a value for the field cannot be obtained
367      * @throws UnsupportedTemporalTypeException if the field is not supported
368      * @throws ArithmeticException if numeric overflow occurs
369      */
370     @Override
getLong(TemporalField field)371     public long getLong(TemporalField field) {
372         if (field == MONTH_OF_YEAR) {
373             return getValue();
374         } else if (field instanceof ChronoField) {
375             throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
376         }
377         return field.getFrom(this);
378     }
379 
380     //-----------------------------------------------------------------------
381     /**
382      * Returns the month-of-year that is the specified number of quarters after this one.
383      * <p>
384      * The calculation rolls around the end of the year from December to January.
385      * The specified period may be negative.
386      * <p>
387      * This instance is immutable and unaffected by this method call.
388      *
389      * @param months  the months to add, positive or negative
390      * @return the resulting month, not null
391      */
plus(long months)392     public Month plus(long months) {
393         int amount = (int) (months % 12);
394         return ENUMS[(ordinal() + (amount + 12)) % 12];
395     }
396 
397     /**
398      * Returns the month-of-year that is the specified number of months before this one.
399      * <p>
400      * The calculation rolls around the start of the year from January to December.
401      * The specified period may be negative.
402      * <p>
403      * This instance is immutable and unaffected by this method call.
404      *
405      * @param months  the months to subtract, positive or negative
406      * @return the resulting month, not null
407      */
minus(long months)408     public Month minus(long months) {
409         return plus(-(months % 12));
410     }
411 
412     //-----------------------------------------------------------------------
413     /**
414      * Gets the length of this month in days.
415      * <p>
416      * This takes a flag to determine whether to return the length for a leap year or not.
417      * <p>
418      * February has 28 days in a standard year and 29 days in a leap year.
419      * April, June, September and November have 30 days.
420      * All other months have 31 days.
421      *
422      * @param leapYear  true if the length is required for a leap year
423      * @return the length of this month in days, from 28 to 31
424      */
length(boolean leapYear)425     public int length(boolean leapYear) {
426         switch (this) {
427             case FEBRUARY:
428                 return (leapYear ? 29 : 28);
429             case APRIL:
430             case JUNE:
431             case SEPTEMBER:
432             case NOVEMBER:
433                 return 30;
434             default:
435                 return 31;
436         }
437     }
438 
439     /**
440      * Gets the minimum length of this month in days.
441      * <p>
442      * February has a minimum length of 28 days.
443      * April, June, September and November have 30 days.
444      * All other months have 31 days.
445      *
446      * @return the minimum length of this month in days, from 28 to 31
447      */
minLength()448     public int minLength() {
449         switch (this) {
450             case FEBRUARY:
451                 return 28;
452             case APRIL:
453             case JUNE:
454             case SEPTEMBER:
455             case NOVEMBER:
456                 return 30;
457             default:
458                 return 31;
459         }
460     }
461 
462     /**
463      * Gets the maximum length of this month in days.
464      * <p>
465      * February has a maximum length of 29 days.
466      * April, June, September and November have 30 days.
467      * All other months have 31 days.
468      *
469      * @return the maximum length of this month in days, from 29 to 31
470      */
maxLength()471     public int maxLength() {
472         switch (this) {
473             case FEBRUARY:
474                 return 29;
475             case APRIL:
476             case JUNE:
477             case SEPTEMBER:
478             case NOVEMBER:
479                 return 30;
480             default:
481                 return 31;
482         }
483     }
484 
485     //-----------------------------------------------------------------------
486     /**
487      * Gets the day-of-year corresponding to the first day of this month.
488      * <p>
489      * This returns the day-of-year that this month begins on, using the leap
490      * year flag to determine the length of February.
491      *
492      * @param leapYear  true if the length is required for a leap year
493      * @return the day of year corresponding to the first day of this month, from 1 to 336
494      */
firstDayOfYear(boolean leapYear)495     public int firstDayOfYear(boolean leapYear) {
496         int leap = leapYear ? 1 : 0;
497         switch (this) {
498             case JANUARY:
499                 return 1;
500             case FEBRUARY:
501                 return 32;
502             case MARCH:
503                 return 60 + leap;
504             case APRIL:
505                 return 91 + leap;
506             case MAY:
507                 return 121 + leap;
508             case JUNE:
509                 return 152 + leap;
510             case JULY:
511                 return 182 + leap;
512             case AUGUST:
513                 return 213 + leap;
514             case SEPTEMBER:
515                 return 244 + leap;
516             case OCTOBER:
517                 return 274 + leap;
518             case NOVEMBER:
519                 return 305 + leap;
520             case DECEMBER:
521             default:
522                 return 335 + leap;
523         }
524     }
525 
526     /**
527      * Gets the month corresponding to the first month of this quarter.
528      * <p>
529      * The year can be divided into four quarters.
530      * This method returns the first month of the quarter for the base month.
531      * January, February and March return January.
532      * April, May and June return April.
533      * July, August and September return July.
534      * October, November and December return October.
535      *
536      * @return the first month of the quarter corresponding to this month, not null
537      */
firstMonthOfQuarter()538     public Month firstMonthOfQuarter() {
539         return ENUMS[(ordinal() / 3) * 3];
540     }
541 
542     //-----------------------------------------------------------------------
543     /**
544      * Queries this month-of-year using the specified query.
545      * <p>
546      * This queries this month-of-year using the specified query strategy object.
547      * The {@code TemporalQuery} object defines the logic to be used to
548      * obtain the result. Read the documentation of the query to understand
549      * what the result of this method will be.
550      * <p>
551      * The result of this method is obtained by invoking the
552      * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
553      * specified query passing {@code this} as the argument.
554      *
555      * @param <R> the type of the result
556      * @param query  the query to invoke, not null
557      * @return the query result, null may be returned (defined by the query)
558      * @throws DateTimeException if unable to query (defined by the query)
559      * @throws ArithmeticException if numeric overflow occurs (defined by the query)
560      */
561     @SuppressWarnings("unchecked")
562     @Override
query(TemporalQuery<R> query)563     public <R> R query(TemporalQuery<R> query) {
564         if (query == TemporalQueries.chronology()) {
565             return (R) IsoChronology.INSTANCE;
566         } else if (query == TemporalQueries.precision()) {
567             return (R) MONTHS;
568         }
569         return TemporalAccessor.super.query(query);
570     }
571 
572     /**
573      * Adjusts the specified temporal object to have this month-of-year.
574      * <p>
575      * This returns a temporal object of the same observable type as the input
576      * with the month-of-year changed to be the same as this.
577      * <p>
578      * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
579      * passing {@link ChronoField#MONTH_OF_YEAR} as the field.
580      * If the specified temporal object does not use the ISO calendar system then
581      * a {@code DateTimeException} is thrown.
582      * <p>
583      * In most cases, it is clearer to reverse the calling pattern by using
584      * {@link Temporal#with(TemporalAdjuster)}:
585      * <pre>
586      *   // these two lines are equivalent, but the second approach is recommended
587      *   temporal = thisMonth.adjustInto(temporal);
588      *   temporal = temporal.with(thisMonth);
589      * </pre>
590      * <p>
591      * For example, given a date in May, the following are output:
592      * <pre>
593      *   dateInMay.with(JANUARY);    // four months earlier
594      *   dateInMay.with(APRIL);      // one months earlier
595      *   dateInMay.with(MAY);        // same date
596      *   dateInMay.with(JUNE);       // one month later
597      *   dateInMay.with(DECEMBER);   // seven months later
598      * </pre>
599      * <p>
600      * This instance is immutable and unaffected by this method call.
601      *
602      * @param temporal  the target object to be adjusted, not null
603      * @return the adjusted object, not null
604      * @throws DateTimeException if unable to make the adjustment
605      * @throws ArithmeticException if numeric overflow occurs
606      */
607     @Override
adjustInto(Temporal temporal)608     public Temporal adjustInto(Temporal temporal) {
609         if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) {
610             throw new DateTimeException("Adjustment only supported on ISO date-time");
611         }
612         return temporal.with(MONTH_OF_YEAR, getValue());
613     }
614 
615 }
616