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
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 {
429 * A hash code for this clock.
430 * <p>
431 * Clocks should override this method based on
432 * their state and to meet the contract of {@link Object#hashCode}.
433 * If not overridden, the behavior is defined by {@link Object#hashCode}
434 *
435 * @return a suitable hash code
436 */
437 @Override
438 public int hashCode() {
439 return super.hashCode();
440 }
441
442 //-----------------------------------------------------------------------
443 /**
444 * Implementation of a clock that always returns the latest time from
445 * {@link System#currentTimeMillis()}.
446 */
447 static final class SystemClock extends Clock implements Serializable {
448 private static final long serialVersionUID = 6740630888130243051L;
449 private final ZoneId zone;
450
451 SystemClock(ZoneId zone) {
452 this.zone = zone;
453 }
454 @Override
455 public ZoneId getZone() {
456 return zone;
457 }
458 @Override
459 public Clock withZone(ZoneId zone) {
460 if (zone.equals(this.zone)) { // intentional NPE
461 return this;
462 }
463 return new SystemClock(zone);
464 }
465 @Override
466 public long millis() {
467 return System.currentTimeMillis();
468 }
469 @Override
470 public Instant instant() {
471 return Instant.ofEpochMilli(millis());
472 }
473 @Override
474 public boolean equals(Object obj) {
475 if (obj instanceof SystemClock) {
476 return zone.equals(((SystemClock) obj).zone);
477 }
478 return false;
479 }
480 @Override
481 public int hashCode() {
482 return zone.hashCode() + 1;
483 }
484 @Override
485 public String toString() {
486 return "SystemClock[" + zone + "]";
487 }
488 }
489
490 //-----------------------------------------------------------------------
491 /**
492 * Implementation of a clock that always returns the same instant.
493 * This is typically used for testing.
494 */
495 static final class FixedClock extends Clock implements Serializable {
496 private static final long serialVersionUID = 7430389292664866958L;
497 private final Instant instant;
498 private final ZoneId zone;
499
500 FixedClock(Instant fixedInstant, ZoneId zone) {
501 this.instant = fixedInstant;
502 this.zone = zone;
503 }
504 @Override
505 public ZoneId getZone() {
506 return zone;
507 }
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1 /*
2 * Copyright (c) 2012, 2015, 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
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 java.io.IOException;
65 import java.io.ObjectInputStream;
66 import static java.time.LocalTime.NANOS_PER_MINUTE;
67 import static java.time.LocalTime.NANOS_PER_SECOND;
68
69 import java.io.Serializable;
70 import java.util.Objects;
71 import java.util.TimeZone;
72 import sun.misc.VM;
73
74 /**
75 * A clock providing access to the current instant, date and time using a time-zone.
76 * <p>
77 * Instances of this class are used to find the current instant, which can be
78 * interpreted using the stored time-zone to find the current date and time.
79 * As such, a clock can be used instead of {@link System#currentTimeMillis()}
80 * and {@link TimeZone#getDefault()}.
81 * <p>
82 * Use of a {@code Clock} is optional. All key date-time classes also have a
83 * {@code now()} factory method that uses the system clock in the default time zone.
84 * The primary purpose of this abstraction is to allow alternate clocks to be
85 * plugged in as and when required. Applications use an object to obtain the
86 * current time rather than a static method. This can simplify testing.
87 * <p>
88 * Best practice for applications is to pass a {@code Clock} into any method
89 * that requires the current instant. A dependency injection framework is one
90 * way to achieve this:
91 * <pre>
92 * public class MyBean {
432 * A hash code for this clock.
433 * <p>
434 * Clocks should override this method based on
435 * their state and to meet the contract of {@link Object#hashCode}.
436 * If not overridden, the behavior is defined by {@link Object#hashCode}
437 *
438 * @return a suitable hash code
439 */
440 @Override
441 public int hashCode() {
442 return super.hashCode();
443 }
444
445 //-----------------------------------------------------------------------
446 /**
447 * Implementation of a clock that always returns the latest time from
448 * {@link System#currentTimeMillis()}.
449 */
450 static final class SystemClock extends Clock implements Serializable {
451 private static final long serialVersionUID = 6740630888130243051L;
452 private static final long OFFSET_SEED =
453 System.currentTimeMillis()/1000 - 1024; // initial offest
454 private final ZoneId zone;
455 // We don't actually need a volatile here.
456 // We don't care if offset is set or read concurrently by multiple
457 // threads - we just need a value which is 'recent enough' - in other
458 // words something that has been updated at least once in the last
459 // 2^32 secs (~136 years). And even if we by chance see an invalid
460 // offset, the worst that can happen is that we will get a -1 value
461 // from getNanoTimeAdjustment, forcing us to update the offset
462 // once again.
463 private transient long offset;
464
465 SystemClock(ZoneId zone) {
466 this.zone = zone;
467 this.offset = OFFSET_SEED;
468 }
469 @Override
470 public ZoneId getZone() {
471 return zone;
472 }
473 @Override
474 public Clock withZone(ZoneId zone) {
475 if (zone.equals(this.zone)) { // intentional NPE
476 return this;
477 }
478 return new SystemClock(zone);
479 }
480 @Override
481 public long millis() {
482 // System.currentTimeMillis() and VM.getNanoTimeAdjustment(offset)
483 // use the same time source - System.currentTimeMillis() simply
484 // limits the resolution to milliseconds.
485 // So we take the faster path and call System.currentTimeMillis()
486 // directly - in order to avoid the performance penalty of
487 // VM.getNanoTimeAdjustment(offset) which is less efficient.
488 return System.currentTimeMillis();
489 }
490 @Override
491 public Instant instant() {
492 // Take a local copy of offset. offset can be updated concurrently
493 // by other threads (even if we haven't made it volatile) so we will
494 // work with a local copy.
495 long localOffset = offset;
496 long adjustment = VM.getNanoTimeAdjustment(localOffset);
497
498 if (adjustment == -1) {
499 // -1 is a sentinel value returned by VM.getNanoTimeAdjustment
500 // when the offset it is given is too far off the current UTC
501 // time. In principle, this should not happen unless the
502 // JVM has run for more than ~136 years (not likely) or
503 // someone is fiddling with the system time, or the offset is
504 // by chance at 1ns in the future (very unlikely).
505 // We can easily recover from all these conditions by bringing
506 // back the offset in range and retry.
507
508 // bring back the offset in range. We use -1024 to make
509 // it more unlikely to hit the 1ns in the future condition.
510 localOffset = System.currentTimeMillis()/1000 - 1024;
511
512 // retry
513 adjustment = VM.getNanoTimeAdjustment(localOffset);
514
515 if (adjustment == -1) {
516 // Should not happen: we just recomputed a new offset.
517 // It should have fixed the issue.
518 throw new InternalError("Offset " + localOffset + " is not in range");
519 } else {
520 // OK - recovery succeeded. Update the offset for the
521 // next call...
522 offset = localOffset;
523 }
524 }
525 return Instant.ofEpochSecond(localOffset, adjustment);
526 }
527 @Override
528 public boolean equals(Object obj) {
529 if (obj instanceof SystemClock) {
530 return zone.equals(((SystemClock) obj).zone);
531 }
532 return false;
533 }
534 @Override
535 public int hashCode() {
536 return zone.hashCode() + 1;
537 }
538 @Override
539 public String toString() {
540 return "SystemClock[" + zone + "]";
541 }
542 private void readObject(ObjectInputStream is)
543 throws IOException, ClassNotFoundException {
544 // ensure that offset is initialized
545 is.defaultReadObject();
546 offset = OFFSET_SEED;
547 }
548 }
549
550 //-----------------------------------------------------------------------
551 /**
552 * Implementation of a clock that always returns the same instant.
553 * This is typically used for testing.
554 */
555 static final class FixedClock extends Clock implements Serializable {
556 private static final long serialVersionUID = 7430389292664866958L;
557 private final Instant instant;
558 private final ZoneId zone;
559
560 FixedClock(Instant fixedInstant, ZoneId zone) {
561 this.instant = fixedInstant;
562 this.zone = zone;
563 }
564 @Override
565 public ZoneId getZone() {
566 return zone;
567 }
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