1 /*
2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * This file is available under and governed by the GNU General Public
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) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
33 *
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions are met:
38 *
39 * * Redistributions of source code must retain the above copyright notice,
40 * this list of conditions and the following disclaimer.
41 *
42 * * Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 *
46 * * Neither the name of JSR-310 nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
61 */
62 package java.time;
63
64 import static java.time.LocalTime.NANOS_PER_MINUTE;
65 import static java.time.LocalTime.NANOS_PER_SECOND;
66
67 import java.io.Serializable;
68 import java.util.Objects;
69 import java.util.TimeZone;
70
71 /**
72 * A clock providing access to the current instant, date and time using a time-zone.
73 * <p>
74 * Instances of this class are used to find the current instant, which can be
75 * interpreted using the stored time-zone to find the current date and time.
76 * As such, a clock can be used instead of {@link System#currentTimeMillis()}
77 * and {@link TimeZone#getDefault()}.
78 * <p>
79 * Use of a {@code Clock} is optional. All key date-time classes also have a
80 * {@code now()} factory method that uses the system clock in the default time zone.
81 * The primary purpose of this abstraction is to allow alternate clocks to be
82 * plugged in as and when required. Applications use an object to obtain the
83 * current time rather than a static method. This can simplify testing.
84 * <p>
85 * Best practice for applications is to pass a {@code Clock} into any method
86 * that requires the current instant. A dependency injection framework is one
87 * way to achieve this:
88 * <pre>
89 * public class MyBean {
90 * private Clock clock; // dependency inject
91 * ...
92 * public void process(LocalDate eventDate) {
93 * if (eventDate.isBefore(LocalDate.now(clock)) {
94 * ...
95 * }
96 * }
97 * }
98 * </pre>
99 * This approach allows an alternate clock, such as {@link #fixed(Instant, ZoneId) fixed}
100 * or {@link #offset(Clock, Duration) offset} to be used during testing.
101 * <p>
102 * The {@code system} factory methods provide clocks based on the best available
103 * system clock This may use {@link System#currentTimeMillis()}, or a higher
104 * resolution clock if one is available.
105 *
106 * <h3>Specification for implementors</h3>
107 * This abstract class must be implemented with care to ensure other operate correctly.
108 * All implementations that can be instantiated must be final, immutable and thread-safe.
109 * <p>
110 * The principal methods are defined to allow the throwing of an exception.
111 * In normal use, no exceptions will be thrown, however one possible implementation would be to
112 * obtain the time from a central time server across the network. Obviously, in this case the
113 * lookup could fail, and so the method is permitted to throw an exception.
114 * <p>
115 * The returned instants from {@code Clock} work on a time-scale that ignores leap seconds.
116 * If the implementation wraps a source that provides leap second information, then a mechanism
117 * should be used to "smooth" the leap second, such as UTC-SLS.
118 * <p>
119 * Implementations should implement {@code Serializable} wherever possible and must
120 * document whether or not they do support serialization.
121 *
122 * @since 1.8
123 */
124 public abstract class Clock {
125
126 /**
127 * Obtains a clock that returns the current instant using the best available
128 * system clock, converting to date and time using the UTC time-zone.
129 * <p>
130 * This clock, rather than {@link #systemDefaultZone()}, should be used when
131 * you need the current instant without the date or time.
132 * <p>
133 * This clock is based on the best available system clock.
134 * This may use {@link System#currentTimeMillis()}, or a higher resolution
135 * clock if one is available.
136 * <p>
137 * Conversion from instant to date or time uses the {@linkplain ZoneOffset#UTC UTC time-zone}.
138 * <p>
139 * The returned implementation is immutable, thread-safe and {@code Serializable}.
140 * It is equivalent to {@code system(ZoneOffset.UTC)}.
141 *
142 * @return a clock that uses the best available system clock in the UTC zone, not null
143 */
144 public static Clock systemUTC() {
145 return new SystemClock(ZoneOffset.UTC);
146 }
147
148 /**
149 * Obtains a clock that returns the current instant using the best available
150 * system clock, converting to date and time using the default time-zone.
151 * <p>
152 * This clock is based on the best available system clock.
153 * This may use {@link System#currentTimeMillis()}, or a higher resolution
154 * clock if one is available.
155 * <p>
156 * Using this method hard codes a dependency to the default time-zone into your application.
157 * It is recommended to avoid this and use a specific time-zone whenever possible.
158 * The {@link #systemUTC() UTC clock} should be used when you need the current instant
159 * without the date or time.
160 * <p>
161 * The returned implementation is immutable, thread-safe and {@code Serializable}.
162 * It is equivalent to {@code system(ZoneId.systemDefault())}.
163 *
164 * @return a clock that uses the best available system clock in the default zone, not null
165 * @see ZoneId#systemDefault()
166 */
167 public static Clock systemDefaultZone() {
168 return new SystemClock(ZoneId.systemDefault());
169 }
170
171 /**
172 * Obtains a clock that returns the current instant using best available
173 * system clock.
174 * <p>
175 * This clock is based on the best available system clock.
176 * This may use {@link System#currentTimeMillis()}, or a higher resolution
177 * clock if one is available.
178 * <p>
179 * Conversion from instant to date or time uses the specified time-zone.
180 * <p>
181 * The returned implementation is immutable, thread-safe and {@code Serializable}.
182 *
183 * @param zone the time-zone to use to convert the instant to date-time, not null
184 * @return a clock that uses the best available system clock in the specified zone, not null
185 */
186 public static Clock system(ZoneId zone) {
187 Objects.requireNonNull(zone, "zone");
188 return new SystemClock(zone);
189 }
190
191 //-------------------------------------------------------------------------
192 /**
193 * Obtains a clock that returns the current instant ticking in whole seconds
194 * using best available system clock.
195 * <p>
196 * This clock will always have the nano-of-second field set to zero.
197 * This ensures that the visible time ticks in whole seconds.
198 * The underlying clock is the best available system clock, equivalent to
199 * using {@link #system(ZoneId)}.
200 * <p>
201 * Implementations may use a caching strategy for performance reasons.
202 * As such, it is possible that the start of the second observed via this
203 * clock will be later than that observed directly via the underlying clock.
204 * <p>
205 * The returned implementation is immutable, thread-safe and {@code Serializable}.
206 * It is equivalent to {@code tick(system(zone), Duration.ofSeconds(1))}.
207 *
208 * @param zone the time-zone to use to convert the instant to date-time, not null
209 * @return a clock that ticks in whole seconds using the specified zone, not null
210 */
211 public static Clock tickSeconds(ZoneId zone) {
212 return new TickClock(system(zone), NANOS_PER_SECOND);
213 }
214
215 /**
216 * Obtains a clock that returns the current instant ticking in whole minutes
217 * using best available system clock.
218 * <p>
219 * This clock will always have the nano-of-second and second-of-minute fields set to zero.
220 * This ensures that the visible time ticks in whole minutes.
221 * The underlying clock is the best available system clock, equivalent to
222 * using {@link #system(ZoneId)}.
223 * <p>
224 * Implementations may use a caching strategy for performance reasons.
225 * As such, it is possible that the start of the minute observed via this
226 * clock will be later than that observed directly via the underlying clock.
227 * <p>
228 * The returned implementation is immutable, thread-safe and {@code Serializable}.
229 * It is equivalent to {@code tick(system(zone), Duration.ofMinutes(1))}.
230 *
231 * @param zone the time-zone to use to convert the instant to date-time, not null
232 * @return a clock that ticks in whole minutes using the specified zone, not null
233 */
234 public static Clock tickMinutes(ZoneId zone) {
235 return new TickClock(system(zone), NANOS_PER_MINUTE);
236 }
237
238 /**
239 * Obtains a clock that returns instants from the specified clock truncated
240 * to the nearest occurrence of the specified duration.
241 * <p>
242 * This clock will only tick as per the specified duration. Thus, if the duration
243 * is half a second, the clock will return instants truncated to the half second.
244 * <p>
245 * The tick duration must be positive. If it has a part smaller than a whole
246 * millisecond, then the whole duration must divide into one second without
247 * leaving a remainder. All normal tick durations will match these criteria,
248 * including any multiple of hours, minutes, seconds and milliseconds, and
249 * sensible nanosecond durations, such as 20ns, 250,000ns and 500,000ns.
250 * <p>
251 * A duration of zero or one nanosecond would have no truncation effect.
252 * Passing one of these will return the underlying clock.
253 * <p>
254 * Implementations may use a caching strategy for performance reasons.
255 * As such, it is possible that the start of the requested duration observed
256 * via this clock will be later than that observed directly via the underlying clock.
257 * <p>
258 * The returned implementation is immutable, thread-safe and {@code Serializable}
259 * providing that the base clock is.
260 *
261 * @param baseClock the base clock to base the ticking clock on, not null
262 * @param tickDuration the duration of each visible tick, not negative, not null
263 * @return a clock that ticks in whole units of the duration, not null
264 * @throws IllegalArgumentException if the duration is negative, or has a
265 * part smaller than a whole millisecond such that the whole duration is not
266 * divisible into one second
267 * @throws ArithmeticException if the duration is too large to be represented as nanos
268 */
269 public static Clock tick(Clock baseClock, Duration tickDuration) {
270 Objects.requireNonNull(baseClock, "baseClock");
271 Objects.requireNonNull(tickDuration, "tickDuration");
272 if (tickDuration.isNegative()) {
273 throw new IllegalArgumentException("Tick duration must not be negative");
274 }
275 long tickNanos = tickDuration.toNanos();
276 if (tickNanos % 1000_000 == 0) {
277 // ok, no fraction of millisecond
278 } else if (1000_000_000 % tickNanos == 0) {
279 // ok, divides into one second without remainder
280 } else {
281 throw new IllegalArgumentException("Invalid tick duration");
282 }
283 if (tickNanos <= 1) {
284 return baseClock;
285 }
286 return new TickClock(baseClock, tickNanos);
287 }
288
289 //-----------------------------------------------------------------------
290 /**
291 * Obtains a clock that always returns the same instant.
292 * <p>
293 * This clock simply returns the specified instant.
294 * As such, it is not a clock in the conventional sense.
295 * The main use case for this is in testing, where the fixed clock ensures
296 * tests are not dependent on the current clock.
297 * <p>
298 * The returned implementation is immutable, thread-safe and {@code Serializable}.
299 *
300 * @param fixedInstant the instant to use as the clock, not null
301 * @param zone the time-zone to use to convert the instant to date-time, not null
302 * @return a clock that always returns the same instant, not null
303 */
304 public static Clock fixed(Instant fixedInstant, ZoneId zone) {
305 Objects.requireNonNull(fixedInstant, "fixedInstant");
306 Objects.requireNonNull(zone, "zone");
307 return new FixedClock(fixedInstant, zone);
308 }
309
310 //-------------------------------------------------------------------------
311 /**
312 * Obtains a clock that returns instants from the specified clock with the
313 * specified duration added
314 * <p>
315 * This clock wraps another clock, returning instants that are later by the
316 * specified duration. If the duration is negative, the instants will be
317 * earlier than the current date and time.
318 * The main use case for this is to simulate running in the future or in the past.
319 * <p>
320 * A duration of zero would have no offsetting effect.
321 * Passing zero will return the underlying clock.
322 * <p>
323 * The returned implementation is immutable, thread-safe and {@code Serializable}
324 * providing that the base clock is.
325 *
326 * @param baseClock the base clock to add the duration to, not null
327 * @param offsetDuration the duration to add, not null
328 * @return a clock based on the base clock with the duration added, not null
329 */
330 public static Clock offset(Clock baseClock, Duration offsetDuration) {
331 Objects.requireNonNull(baseClock, "baseClock");
332 Objects.requireNonNull(offsetDuration, "offsetDuration");
333 if (offsetDuration.equals(Duration.ZERO)) {
334 return baseClock;
335 }
336 return new OffsetClock(baseClock, offsetDuration);
337 }
338
339 //-----------------------------------------------------------------------
340 /**
341 * Constructor accessible by subclasses.
342 */
343 protected Clock() {
344 }
345
346 //-----------------------------------------------------------------------
347 /**
348 * Gets the time-zone being used to create dates and times.
349 * <p>
350 * A clock will typically obtain the current instant and then convert that
351 * to a date or time using a time-zone. This method returns the time-zone used.
352 *
353 * @return the time-zone being used to interpret instants, not null
354 */
355 public abstract ZoneId getZone();
356
357 /**
358 * Returns a copy of this clock with a different time-zone.
359 * <p>
360 * A clock will typically obtain the current instant and then convert that
361 * to a date or time using a time-zone. This method returns a clock with
362 * similar properties but using a different time-zone.
363 *
364 * @param zone the time-zone to change to, not null
365 * @return a clock based on this clock with the specified time-zone, not null
366 */
367 public abstract Clock withZone(ZoneId zone);
368
369 //-------------------------------------------------------------------------
370 /**
371 * Gets the current millisecond instant of the clock.
372 * <p>
373 * This returns the millisecond-based instant, measured from 1970-01-01T00:00 UTC.
374 * This is equivalent to the definition of {@link System#currentTimeMillis()}.
375 * <p>
376 * Most applications should avoid this method and use {@link Instant} to represent
377 * an instant on the time-line rather than a raw millisecond value.
378 * This method is provided to allow the use of the clock in high performance use cases
379 * where the creation of an object would be unacceptable.
380 *
381 * @return the current millisecond instant from this clock, measured from
382 * the Java epoch of 1970-01-01T00:00 UTC, not null
383 * @throws DateTimeException if the instant cannot be obtained, not thrown by most implementations
384 */
385 public abstract long millis();
386
387 //-----------------------------------------------------------------------
388 /**
389 * Gets the current instant of the clock.
390 * <p>
391 * This returns an instant representing the current instant as defined by the clock.
392 * <p>
393 * The default implementation currently calls {@link #millis}.
394 *
395 * @return the current instant from this clock, not null
396 * @throws DateTimeException if the instant cannot be obtained, not thrown by most implementations
397 */
398 public Instant instant() {
399 return Instant.ofEpochMilli(millis());
400 }
401
402 //-----------------------------------------------------------------------
403 /**
404 * Checks if this clock is equal to another clock.
405 * <p>
406 * Clocks must compare equal based on their state and behavior.
407 *
408 * @param obj the object to check, null returns false
409 * @return true if this is equal to the other clock
410 */
411 @Override
412 public abstract boolean equals(Object obj);
413
414 /**
415 * A hash code for this clock.
416 *
417 * @return a suitable hash code
418 */
419 @Override
420 public abstract int hashCode();
421
422 //-----------------------------------------------------------------------
423 /**
424 * Returns a string describing this clock.
425 * <p>
426 * Clocks must have a string representation based on their state and behavior.
427 * For example, 'System[Europe/Paris]' could be used to represent the System
428 * clock in the 'Europe/Paris' time-zone.
429 *
430 * @return a string representation of this clock, not null
431 */
432 @Override
433 public abstract String toString();
434
435 //-----------------------------------------------------------------------
436 /**
437 * Implementation of a clock that always returns the latest time from
438 * {@link System#currentTimeMillis()}.
439 */
440 static final class SystemClock extends Clock implements Serializable {
441 private static final long serialVersionUID = 6740630888130243051L;
442 private final ZoneId zone;
443
444 SystemClock(ZoneId zone) {
445 this.zone = zone;
446 }
447 @Override
448 public ZoneId getZone() {
449 return zone;
450 }
451 @Override
452 public Clock withZone(ZoneId zone) {
453 if (zone.equals(this.zone)) { // intentional NPE
454 return this;
455 }
456 return new SystemClock(zone);
457 }
458 @Override
459 public long millis() {
460 return System.currentTimeMillis();
461 }
462 @Override
463 public boolean equals(Object obj) {
464 if (obj instanceof SystemClock) {
465 return zone.equals(((SystemClock) obj).zone);
466 }
467 return false;
468 }
469 @Override
470 public int hashCode() {
471 return zone.hashCode() + 1;
472 }
473 @Override
474 public String toString() {
475 return "SystemClock[" + zone + "]";
476 }
477 }
478
479 //-----------------------------------------------------------------------
480 /**
481 * Implementation of a clock that always returns the same instant.
482 * This is typically used for testing.
483 */
484 static final class FixedClock extends Clock implements Serializable {
485 private static final long serialVersionUID = 7430389292664866958L;
486 private final Instant instant;
487 private final ZoneId zone;
488
489 FixedClock(Instant fixedInstant, ZoneId zone) {
490 this.instant = fixedInstant;
491 this.zone = zone;
492 }
493 @Override
494 public ZoneId getZone() {
495 return zone;
496 }
497 @Override
498 public Clock withZone(ZoneId zone) {
499 if (zone.equals(this.zone)) { // intentional NPE
500 return this;
501 }
502 return new FixedClock(instant, zone);
503 }
504 @Override
505 public long millis() {
506 return instant.toEpochMilli();
507 }
508 @Override
509 public Instant instant() {
510 return instant;
511 }
512 @Override
513 public boolean equals(Object obj) {
514 if (obj instanceof FixedClock) {
515 FixedClock other = (FixedClock) obj;
516 return instant.equals(other.instant) && zone.equals(other.zone);
517 }
518 return false;
519 }
520 @Override
521 public int hashCode() {
522 return instant.hashCode() ^ zone.hashCode();
523 }
524 @Override
525 public String toString() {
526 return "FixedClock[" + instant + "," + zone + "]";
527 }
528 }
529
530 //-----------------------------------------------------------------------
531 /**
532 * Implementation of a clock that adds an offset to an underlying clock.
533 */
534 static final class OffsetClock extends Clock implements Serializable {
535 private static final long serialVersionUID = 2007484719125426256L;
536 private final Clock baseClock;
537 private final Duration offset;
538
539 OffsetClock(Clock baseClock, Duration offset) {
540 this.baseClock = baseClock;
541 this.offset = offset;
542 }
543 @Override
544 public ZoneId getZone() {
545 return baseClock.getZone();
546 }
547 @Override
548 public Clock withZone(ZoneId zone) {
549 if (zone.equals(baseClock.getZone())) { // intentional NPE
550 return this;
551 }
552 return new OffsetClock(baseClock.withZone(zone), offset);
553 }
554 @Override
555 public long millis() {
556 return Math.addExact(baseClock.millis(), offset.toMillis());
557 }
558 @Override
559 public Instant instant() {
560 return baseClock.instant().plus(offset);
561 }
562 @Override
563 public boolean equals(Object obj) {
564 if (obj instanceof OffsetClock) {
565 OffsetClock other = (OffsetClock) obj;
566 return baseClock.equals(other.baseClock) && offset.equals(other.offset);
567 }
568 return false;
569 }
570 @Override
571 public int hashCode() {
572 return baseClock.hashCode() ^ offset.hashCode();
573 }
574 @Override
575 public String toString() {
576 return "OffsetClock[" + baseClock + "," + offset + "]";
577 }
578 }
579
580 //-----------------------------------------------------------------------
581 /**
582 * Implementation of a clock that adds an offset to an underlying clock.
583 */
584 static final class TickClock extends Clock implements Serializable {
585 private static final long serialVersionUID = 6504659149906368850L;
586 private final Clock baseClock;
587 private final long tickNanos;
588
589 TickClock(Clock baseClock, long tickNanos) {
590 this.baseClock = baseClock;
591 this.tickNanos = tickNanos;
592 }
593 @Override
594 public ZoneId getZone() {
595 return baseClock.getZone();
596 }
597 @Override
598 public Clock withZone(ZoneId zone) {
599 if (zone.equals(baseClock.getZone())) { // intentional NPE
600 return this;
601 }
602 return new TickClock(baseClock.withZone(zone), tickNanos);
603 }
604 @Override
605 public long millis() {
606 long millis = baseClock.millis();
607 return millis - Math.floorMod(millis, tickNanos / 1000_000L);
608 }
609 @Override
610 public Instant instant() {
611 if ((tickNanos % 1000_000) == 0) {
612 long millis = baseClock.millis();
613 return Instant.ofEpochMilli(millis - Math.floorMod(millis, tickNanos / 1000_000L));
614 }
615 Instant instant = baseClock.instant();
616 long nanos = instant.getNano();
617 long adjust = Math.floorMod(nanos, tickNanos);
618 return instant.minusNanos(adjust);
619 }
620 @Override
621 public boolean equals(Object obj) {
622 if (obj instanceof TickClock) {
623 TickClock other = (TickClock) obj;
624 return baseClock.equals(other.baseClock) && tickNanos == other.tickNanos;
625 }
626 return false;
627 }
628 @Override
629 public int hashCode() {
630 return baseClock.hashCode() ^ ((int) (tickNanos ^ (tickNanos >>> 32)));
631 }
632 @Override
633 public String toString() {
634 return "TickClock[" + baseClock + "," + Duration.ofNanos(tickNanos) + "]";
635 }
636 }
637
638 }