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26  /*
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28   * License version 2 only, as published by the Free Software Foundation.
29   * However, the following notice accompanied the original version of this
30   * file:
31   *
32   * Copyright (c) 2013, Stephen Colebourne & Michael Nascimento Santos
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62  package java.time.chrono;
63  
64  import java.time.DateTimeException;
65  import java.time.temporal.ChronoUnit;
66  import java.time.temporal.Temporal;
67  import java.time.temporal.TemporalAmount;
68  import java.time.temporal.TemporalUnit;
69  import java.time.temporal.UnsupportedTemporalTypeException;
70  import java.util.List;
71  import java.util.Objects;
72  
73  /**
74   * A date-based amount of time, such as '3 years, 4 months and 5 days' in an
75   * arbitrary chronology, intended for advanced globalization use cases.
76   * <p>
77   * This interface models a date-based amount of time in a calendar system.
78   * While most calendar systems use years, months and days, some do not.
79   * Therefore, this interface operates solely in terms of a set of supported
80   * units that are defined by the {@code Chronology}.
81   * The set of supported units is fixed for a given chronology.
82   * The amount of a supported unit may be set to zero.
83   * <p>
84   * The period is modeled as a directed amount of time, meaning that individual
85   * parts of the period may be negative.
86   *
87   * @implSpec
88   * This interface must be implemented with care to ensure other classes operate correctly.
89   * All implementations that can be instantiated must be final, immutable and thread-safe.
90   * Subclasses should be Serializable wherever possible.
91   *
92   * @since 1.8
93   */
94  public interface ChronoPeriod
95          extends TemporalAmount {
96  
97      /**
98       * Obtains a {@code ChronoPeriod} consisting of amount of time between two dates.
99       * <p>
100      * The start date is included, but the end date is not.
101      * The period is calculated using {@link ChronoLocalDate#until(ChronoLocalDate)}.
102      * As such, the calculation is chronology specific.
103      * <p>
104      * The chronology of the first date is used.
105      * The chronology of the second date is ignored, with the date being converted
106      * to the target chronology system before the calculation starts.
107      * <p>
108      * The result of this method can be a negative period if the end is before the start.
109      * In most cases, the positive/negative sign will be the same in each of the supported fields.
110      *
111      * @param startDateInclusive  the start date, inclusive, specifying the chronology of the calculation, not null
112      * @param endDateExclusive  the end date, exclusive, in any chronology, not null
113      * @return the period between this date and the end date, not null
114      * @see ChronoLocalDate#until(ChronoLocalDate)
115      */
116     public static ChronoPeriod between(ChronoLocalDate startDateInclusive, ChronoLocalDate endDateExclusive) {
117         Objects.requireNonNull(startDateInclusive, "startDateInclusive");
118         Objects.requireNonNull(endDateExclusive, "endDateExclusive");
119         return startDateInclusive.until(endDateExclusive);
120     }
121 
122     //-----------------------------------------------------------------------
123     /**
124      * Gets the value of the requested unit.
125      * <p>
126      * The supported units are chronology specific.
127      * They will typically be {@link ChronoUnit#YEARS YEARS},
128      * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
129      * Requesting an unsupported unit will throw an exception.
130      *
131      * @param unit the {@code TemporalUnit} for which to return the value
132      * @return the long value of the unit
133      * @throws DateTimeException if the unit is not supported
134      * @throws UnsupportedTemporalTypeException if the unit is not supported
135      */
136     @Override
137     long get(TemporalUnit unit);
138 
139     /**
140      * Gets the set of units supported by this period.
141      * <p>
142      * The supported units are chronology specific.
143      * They will typically be {@link ChronoUnit#YEARS YEARS},
144      * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.
145      * They are returned in order from largest to smallest.
146      * <p>
147      * This set can be used in conjunction with {@link #get(TemporalUnit)}
148      * to access the entire state of the period.
149      *
150      * @return a list containing the supported units, not null
151      */
152     @Override
153     List<TemporalUnit> getUnits();
154 
155     /**
156      * Gets the chronology that defines the meaning of the supported units.
157      * <p>
158      * The period is defined by the chronology.
159      * It controls the supported units and restricts addition/subtraction
160      * to {@code ChronoLocalDate} instances of the same chronology.
161      *
162      * @return the chronology defining the period, not null
163      */
164     Chronology getChronology();
165 
166     //-----------------------------------------------------------------------
167     /**
168      * Checks if all the supported units of this period are zero.
169      *
170      * @return true if this period is zero-length
171      */
172     default boolean isZero() {
173         for (TemporalUnit unit : getUnits()) {
174             if (get(unit) != 0) {
175                 return false;
176             }
177         }
178         return true;
179     }
180 
181     /**
182      * Checks if any of the supported units of this period are negative.
183      *
184      * @return true if any unit of this period is negative
185      */
186     default boolean isNegative() {
187         for (TemporalUnit unit : getUnits()) {
188             if (get(unit) < 0) {
189                 return true;
190             }
191         }
192         return false;
193     }
194 
195     //-----------------------------------------------------------------------
196     /**
197      * Returns a copy of this period with the specified period added.
198      * <p>
199      * If the specified amount is a {@code ChronoPeriod} then it must have
200      * the same chronology as this period. Implementations may choose to
201      * accept or reject other {@code TemporalAmount} implementations.
202      * <p>
203      * This instance is immutable and unaffected by this method call.
204      *
205      * @param amountToAdd  the period to add, not null
206      * @return a {@code ChronoPeriod} based on this period with the requested period added, not null
207      * @throws ArithmeticException if numeric overflow occurs
208      */
209     ChronoPeriod plus(TemporalAmount amountToAdd);
210 
211     /**
212      * Returns a copy of this period with the specified period subtracted.
213      * <p>
214      * If the specified amount is a {@code ChronoPeriod} then it must have
215      * the same chronology as this period. Implementations may choose to
216      * accept or reject other {@code TemporalAmount} implementations.
217      * <p>
218      * This instance is immutable and unaffected by this method call.
219      *
220      * @param amountToSubtract  the period to subtract, not null
221      * @return a {@code ChronoPeriod} based on this period with the requested period subtracted, not null
222      * @throws ArithmeticException if numeric overflow occurs
223      */
224     ChronoPeriod minus(TemporalAmount amountToSubtract);
225 
226     //-----------------------------------------------------------------------
227     /**
228      * Returns a new instance with each amount in this period in this period
229      * multiplied by the specified scalar.
230      * <p>
231      * This returns a period with each supported unit individually multiplied.
232      * For example, a period of "2 years, -3 months and 4 days" multiplied by
233      * 3 will return "6 years, -9 months and 12 days".
234      * No normalization is performed.
235      *
236      * @param scalar  the scalar to multiply by, not null
237      * @return a {@code ChronoPeriod} based on this period with the amounts multiplied
238      *  by the scalar, not null
239      * @throws ArithmeticException if numeric overflow occurs
240      */
241     ChronoPeriod multipliedBy(int scalar);
242 
243     /**
244      * Returns a new instance with each amount in this period negated.
245      * <p>
246      * This returns a period with each supported unit individually negated.
247      * For example, a period of "2 years, -3 months and 4 days" will be
248      * negated to "-2 years, 3 months and -4 days".
249      * No normalization is performed.
250      *
251      * @return a {@code ChronoPeriod} based on this period with the amounts negated, not null
252      * @throws ArithmeticException if numeric overflow occurs, which only happens if
253      *  one of the units has the value {@code Long.MIN_VALUE}
254      */
255     default ChronoPeriod negated() {
256         return multipliedBy(-1);
257     }
258 
259     //-----------------------------------------------------------------------
260     /**
261      * Returns a copy of this period with the amounts of each unit normalized.
262      * <p>
263      * The process of normalization is specific to each calendar system.
264      * For example, in the ISO calendar system, the years and months are
265      * normalized but the days are not, such that "15 months" would be
266      * normalized to "1 year and 3 months".
267      * <p>
268      * This instance is immutable and unaffected by this method call.
269      *
270      * @return a {@code ChronoPeriod} based on this period with the amounts of each
271      *  unit normalized, not null
272      * @throws ArithmeticException if numeric overflow occurs
273      */
274     ChronoPeriod normalized();
275 
276     //-------------------------------------------------------------------------
277     /**
278      * Adds this period to the specified temporal object.
279      * <p>
280      * This returns a temporal object of the same observable type as the input
281      * with this period added.
282      * <p>
283      * In most cases, it is clearer to reverse the calling pattern by using
284      * {@link Temporal#plus(TemporalAmount)}.
285      * <pre>
286      *   // these two lines are equivalent, but the second approach is recommended
287      *   dateTime = thisPeriod.addTo(dateTime);
288      *   dateTime = dateTime.plus(thisPeriod);
289      * </pre>
290      * <p>
291      * The specified temporal must have the same chronology as this period.
292      * This returns a temporal with the non-zero supported units added.
293      * <p>
294      * This instance is immutable and unaffected by this method call.
295      *
296      * @param temporal  the temporal object to adjust, not null
297      * @return an object of the same type with the adjustment made, not null
298      * @throws DateTimeException if unable to add
299      * @throws ArithmeticException if numeric overflow occurs
300      */
301     @Override
302     Temporal addTo(Temporal temporal);
303 
304     /**
305      * Subtracts this period from the specified temporal object.
306      * <p>
307      * This returns a temporal object of the same observable type as the input
308      * with this period subtracted.
309      * <p>
310      * In most cases, it is clearer to reverse the calling pattern by using
311      * {@link Temporal#minus(TemporalAmount)}.
312      * <pre>
313      *   // these two lines are equivalent, but the second approach is recommended
314      *   dateTime = thisPeriod.subtractFrom(dateTime);
315      *   dateTime = dateTime.minus(thisPeriod);
316      * </pre>
317      * <p>
318      * The specified temporal must have the same chronology as this period.
319      * This returns a temporal with the non-zero supported units subtracted.
320      * <p>
321      * This instance is immutable and unaffected by this method call.
322      *
323      * @param temporal  the temporal object to adjust, not null
324      * @return an object of the same type with the adjustment made, not null
325      * @throws DateTimeException if unable to subtract
326      * @throws ArithmeticException if numeric overflow occurs
327      */
328     @Override
329     Temporal subtractFrom(Temporal temporal);
330 
331     //-----------------------------------------------------------------------
332     /**
333      * Checks if this period is equal to another period, including the chronology.
334      * <p>
335      * Compares this period with another ensuring that the type, each amount and
336      * the chronology are the same.
337      * Note that this means that a period of "15 Months" is not equal to a period
338      * of "1 Year and 3 Months".
339      *
340      * @param obj  the object to check, null returns false
341      * @return true if this is equal to the other period
342      */
343     @Override
344     boolean equals(Object obj);
345 
346     /**
347      * A hash code for this period.
348      *
349      * @return a suitable hash code
350      */
351     @Override
352     int hashCode();
353 
354     //-----------------------------------------------------------------------
355     /**
356      * Outputs this period as a {@code String}.
357      * <p>
358      * The output will include the period amounts and chronology.
359      *
360      * @return a string representation of this period, not null
361      */
362     @Override
363     String toString();
364 
365 }