-
Clock
-
systemUTC(): Clock
-
systemDefaultZone(): Clock
-
system(ZoneId): Clock
-
tickMillis(ZoneId): Clock
-
tickSeconds(ZoneId): Clock
-
tickMinutes(ZoneId): Clock
-
tick(Clock, Duration): Clock
-
fixed(Instant, ZoneId): Clock
-
offset(Clock, Duration): Clock
-
Clock(): void
-
getZone(): ZoneId
-
withZone(ZoneId): Clock
-
millis(): long
-
instant(): Instant
-
equals(Object): boolean
-
hashCode(): int
-
SystemClock
-
FixedClock
-
OffsetClock
-
TickClock
-
/*
* Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of JSR-310 nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package java.time;
import java.io.IOException;
import java.io.ObjectInputStream;
import static java.time.LocalTime.NANOS_PER_MINUTE;
import static java.time.LocalTime.NANOS_PER_SECOND;
import static java.time.LocalTime.NANOS_PER_MILLI;
import java.io.Serializable;
import java.util.Objects;
import java.util.TimeZone;
import jdk.internal.misc.VM;
A clock providing access to the current instant, date and time using a time-zone.
Instances of this class are used to find the current instant, which can be interpreted using the stored time-zone to find the current date and time. As such, a clock can be used instead of System.currentTimeMillis() and TimeZone.getDefault().
Use of a Clock is optional. All key date-time classes also have a now() factory method that uses the system clock in the default time zone. The primary purpose of this abstraction is to allow alternate clocks to be plugged in as and when required. Applications use an object to obtain the current time rather than a static method. This can simplify testing.
Best practice for applications is to pass a Clock into any method that requires the current instant. A dependency injection framework is one way to achieve this:
public class MyBean {
private Clock clock; // dependency inject
...
public void process(LocalDate eventDate) {
if (eventDate.isBefore(LocalDate.now(clock)) {
...
}
}
}
This approach allows an alternate clock, such as fixed or offset to be used during testing. The system factory methods provide clocks based on the best available system clock This may use System.currentTimeMillis(), or a higher resolution clock if one is available.
Implementation Requirements:
This abstract class must be implemented with care to ensure other classes operate correctly.
All implementations that can be instantiated must be final, immutable and thread-safe.
The principal methods are defined to allow the throwing of an exception.
In normal use, no exceptions will be thrown, however one possible implementation would be to
obtain the time from a central time server across the network. Obviously, in this case the
lookup could fail, and so the method is permitted to throw an exception.
The returned instants from Clock work on a time-scale that ignores leap seconds, as described in Instant. If the implementation wraps a source that provides leap second information, then a mechanism should be used to "smooth" the leap second. The Java Time-Scale mandates the use of UTC-SLS, however clock implementations may choose how accurate they are with the time-scale so long as they document how they work. Implementations are therefore not required to actually perform the UTC-SLS slew or to otherwise be aware of leap seconds.
Implementations should implement Serializable wherever possible and must document whether or not they do support serialization.
Implementation Note: The clock implementation provided here is based on the same underlying clock as System.currentTimeMillis(), but may have a precision finer than milliseconds if available. However, little to no guarantee is provided about the accuracy of the underlying clock. Applications requiring a more accurate clock must implement this abstract class themselves using a different external clock, such as an NTP server. Since: 1.8
/**
* A clock providing access to the current instant, date and time using a time-zone.
* <p>
* Instances of this class are used to find the current instant, which can be
* interpreted using the stored time-zone to find the current date and time.
* As such, a clock can be used instead of {@link System#currentTimeMillis()}
* and {@link TimeZone#getDefault()}.
* <p>
* Use of a {@code Clock} is optional. All key date-time classes also have a
* {@code now()} factory method that uses the system clock in the default time zone.
* The primary purpose of this abstraction is to allow alternate clocks to be
* plugged in as and when required. Applications use an object to obtain the
* current time rather than a static method. This can simplify testing.
* <p>
* Best practice for applications is to pass a {@code Clock} into any method
* that requires the current instant. A dependency injection framework is one
* way to achieve this:
* <pre>
* public class MyBean {
* private Clock clock; // dependency inject
* ...
* public void process(LocalDate eventDate) {
* if (eventDate.isBefore(LocalDate.now(clock)) {
* ...
* }
* }
* }
* </pre>
* This approach allows an alternate clock, such as {@link #fixed(Instant, ZoneId) fixed}
* or {@link #offset(Clock, Duration) offset} to be used during testing.
* <p>
* The {@code system} factory methods provide clocks based on the best available
* system clock This may use {@link System#currentTimeMillis()}, or a higher
* resolution clock if one is available.
*
* @implSpec
* This abstract class must be implemented with care to ensure other classes operate correctly.
* All implementations that can be instantiated must be final, immutable and thread-safe.
* <p>
* The principal methods are defined to allow the throwing of an exception.
* In normal use, no exceptions will be thrown, however one possible implementation would be to
* obtain the time from a central time server across the network. Obviously, in this case the
* lookup could fail, and so the method is permitted to throw an exception.
* <p>
* The returned instants from {@code Clock} work on a time-scale that ignores leap seconds,
* as described in {@link Instant}. If the implementation wraps a source that provides leap
* second information, then a mechanism should be used to "smooth" the leap second.
* The Java Time-Scale mandates the use of UTC-SLS, however clock implementations may choose
* how accurate they are with the time-scale so long as they document how they work.
* Implementations are therefore not required to actually perform the UTC-SLS slew or to
* otherwise be aware of leap seconds.
* <p>
* Implementations should implement {@code Serializable} wherever possible and must
* document whether or not they do support serialization.
*
* @implNote
* The clock implementation provided here is based on the same underlying clock
* as {@link System#currentTimeMillis()}, but may have a precision finer than
* milliseconds if available.
* However, little to no guarantee is provided about the accuracy of the
* underlying clock. Applications requiring a more accurate clock must implement
* this abstract class themselves using a different external clock, such as an
* NTP server.
*
* @since 1.8
*/
public abstract class Clock {
Obtains a clock that returns the current instant using the best available
system clock, converting to date and time using the UTC time-zone.
This clock, rather than systemDefaultZone(), should be used when you need the current instant without the date or time.
This clock is based on the best available system clock. This may use System.currentTimeMillis(), or a higher resolution clock if one is available.
Conversion from instant to date or time uses the UTC time-zone.
The returned implementation is immutable, thread-safe and Serializable. It is equivalent to system(ZoneOffset.UTC).
Returns: a clock that uses the best available system clock in the UTC zone, not null
/**
* Obtains a clock that returns the current instant using the best available
* system clock, converting to date and time using the UTC time-zone.
* <p>
* This clock, rather than {@link #systemDefaultZone()}, should be used when
* you need the current instant without the date or time.
* <p>
* This clock is based on the best available system clock.
* This may use {@link System#currentTimeMillis()}, or a higher resolution
* clock if one is available.
* <p>
* Conversion from instant to date or time uses the {@linkplain ZoneOffset#UTC UTC time-zone}.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
* It is equivalent to {@code system(ZoneOffset.UTC)}.
*
* @return a clock that uses the best available system clock in the UTC zone, not null
*/
public static Clock systemUTC() {
return SystemClock.UTC;
}
Obtains a clock that returns the current instant using the best available
system clock, converting to date and time using the default time-zone.
This clock is based on the best available system clock. This may use System.currentTimeMillis(), or a higher resolution clock if one is available.
Using this method hard codes a dependency to the default time-zone into your application. It is recommended to avoid this and use a specific time-zone whenever possible. The UTC clock should be used when you need the current instant without the date or time.
The returned implementation is immutable, thread-safe and Serializable. It is equivalent to system(ZoneId.systemDefault()).
See Also: Returns: a clock that uses the best available system clock in the default zone, not null
/**
* Obtains a clock that returns the current instant using the best available
* system clock, converting to date and time using the default time-zone.
* <p>
* This clock is based on the best available system clock.
* This may use {@link System#currentTimeMillis()}, or a higher resolution
* clock if one is available.
* <p>
* Using this method hard codes a dependency to the default time-zone into your application.
* It is recommended to avoid this and use a specific time-zone whenever possible.
* The {@link #systemUTC() UTC clock} should be used when you need the current instant
* without the date or time.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
* It is equivalent to {@code system(ZoneId.systemDefault())}.
*
* @return a clock that uses the best available system clock in the default zone, not null
* @see ZoneId#systemDefault()
*/
public static Clock systemDefaultZone() {
return new SystemClock(ZoneId.systemDefault());
}
Obtains a clock that returns the current instant using the best available
system clock.
This clock is based on the best available system clock. This may use System.currentTimeMillis(), or a higher resolution clock if one is available.
Conversion from instant to date or time uses the specified time-zone.
The returned implementation is immutable, thread-safe and Serializable.
Params: - zone – the time-zone to use to convert the instant to date-time, not null
Returns: a clock that uses the best available system clock in the specified zone, not null
/**
* Obtains a clock that returns the current instant using the best available
* system clock.
* <p>
* This clock is based on the best available system clock.
* This may use {@link System#currentTimeMillis()}, or a higher resolution
* clock if one is available.
* <p>
* Conversion from instant to date or time uses the specified time-zone.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
*
* @param zone the time-zone to use to convert the instant to date-time, not null
* @return a clock that uses the best available system clock in the specified zone, not null
*/
public static Clock system(ZoneId zone) {
Objects.requireNonNull(zone, "zone");
if (zone == ZoneOffset.UTC) {
return SystemClock.UTC;
}
return new SystemClock(zone);
}
//-------------------------------------------------------------------------
Obtains a clock that returns the current instant ticking in whole milliseconds
using the best available system clock.
This clock will always have the nano-of-second field truncated to milliseconds. This ensures that the visible time ticks in whole milliseconds. The underlying clock is the best available system clock, equivalent to using system(ZoneId).
Implementations may use a caching strategy for performance reasons.
As such, it is possible that the start of the millisecond observed via this
clock will be later than that observed directly via the underlying clock.
The returned implementation is immutable, thread-safe and Serializable. It is equivalent to tick(system(zone), Duration.ofMillis(1)).
Params: - zone – the time-zone to use to convert the instant to date-time, not null
Returns: a clock that ticks in whole milliseconds using the specified zone, not null Since: 9
/**
* Obtains a clock that returns the current instant ticking in whole milliseconds
* using the best available system clock.
* <p>
* This clock will always have the nano-of-second field truncated to milliseconds.
* This ensures that the visible time ticks in whole milliseconds.
* The underlying clock is the best available system clock, equivalent to
* using {@link #system(ZoneId)}.
* <p>
* Implementations may use a caching strategy for performance reasons.
* As such, it is possible that the start of the millisecond observed via this
* clock will be later than that observed directly via the underlying clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
* It is equivalent to {@code tick(system(zone), Duration.ofMillis(1))}.
*
* @param zone the time-zone to use to convert the instant to date-time, not null
* @return a clock that ticks in whole milliseconds using the specified zone, not null
* @since 9
*/
public static Clock tickMillis(ZoneId zone) {
return new TickClock(system(zone), NANOS_PER_MILLI);
}
//-------------------------------------------------------------------------
Obtains a clock that returns the current instant ticking in whole seconds
using the best available system clock.
This clock will always have the nano-of-second field set to zero. This ensures that the visible time ticks in whole seconds. The underlying clock is the best available system clock, equivalent to using system(ZoneId).
Implementations may use a caching strategy for performance reasons.
As such, it is possible that the start of the second observed via this
clock will be later than that observed directly via the underlying clock.
The returned implementation is immutable, thread-safe and Serializable. It is equivalent to tick(system(zone), Duration.ofSeconds(1)).
Params: - zone – the time-zone to use to convert the instant to date-time, not null
Returns: a clock that ticks in whole seconds using the specified zone, not null
/**
* Obtains a clock that returns the current instant ticking in whole seconds
* using the best available system clock.
* <p>
* This clock will always have the nano-of-second field set to zero.
* This ensures that the visible time ticks in whole seconds.
* The underlying clock is the best available system clock, equivalent to
* using {@link #system(ZoneId)}.
* <p>
* Implementations may use a caching strategy for performance reasons.
* As such, it is possible that the start of the second observed via this
* clock will be later than that observed directly via the underlying clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
* It is equivalent to {@code tick(system(zone), Duration.ofSeconds(1))}.
*
* @param zone the time-zone to use to convert the instant to date-time, not null
* @return a clock that ticks in whole seconds using the specified zone, not null
*/
public static Clock tickSeconds(ZoneId zone) {
return new TickClock(system(zone), NANOS_PER_SECOND);
}
Obtains a clock that returns the current instant ticking in whole minutes
using the best available system clock.
This clock will always have the nano-of-second and second-of-minute fields set to zero. This ensures that the visible time ticks in whole minutes. The underlying clock is the best available system clock, equivalent to using system(ZoneId).
Implementations may use a caching strategy for performance reasons.
As such, it is possible that the start of the minute observed via this
clock will be later than that observed directly via the underlying clock.
The returned implementation is immutable, thread-safe and Serializable. It is equivalent to tick(system(zone), Duration.ofMinutes(1)).
Params: - zone – the time-zone to use to convert the instant to date-time, not null
Returns: a clock that ticks in whole minutes using the specified zone, not null
/**
* Obtains a clock that returns the current instant ticking in whole minutes
* using the best available system clock.
* <p>
* This clock will always have the nano-of-second and second-of-minute fields set to zero.
* This ensures that the visible time ticks in whole minutes.
* The underlying clock is the best available system clock, equivalent to
* using {@link #system(ZoneId)}.
* <p>
* Implementations may use a caching strategy for performance reasons.
* As such, it is possible that the start of the minute observed via this
* clock will be later than that observed directly via the underlying clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
* It is equivalent to {@code tick(system(zone), Duration.ofMinutes(1))}.
*
* @param zone the time-zone to use to convert the instant to date-time, not null
* @return a clock that ticks in whole minutes using the specified zone, not null
*/
public static Clock tickMinutes(ZoneId zone) {
return new TickClock(system(zone), NANOS_PER_MINUTE);
}
Obtains a clock that returns instants from the specified clock truncated
to the nearest occurrence of the specified duration.
This clock will only tick as per the specified duration. Thus, if the duration
is half a second, the clock will return instants truncated to the half second.
The tick duration must be positive. If it has a part smaller than a whole
millisecond, then the whole duration must divide into one second without
leaving a remainder. All normal tick durations will match these criteria,
including any multiple of hours, minutes, seconds and milliseconds, and
sensible nanosecond durations, such as 20ns, 250,000ns and 500,000ns.
A duration of zero or one nanosecond would have no truncation effect.
Passing one of these will return the underlying clock.
Implementations may use a caching strategy for performance reasons.
As such, it is possible that the start of the requested duration observed
via this clock will be later than that observed directly via the underlying clock.
The returned implementation is immutable, thread-safe and Serializable providing that the base clock is.
Params: - baseClock – the base clock to base the ticking clock on, not null
- tickDuration – the duration of each visible tick, not negative, not null
Throws: - IllegalArgumentException – if the duration is negative, or has a
part smaller than a whole millisecond such that the whole duration is not
divisible into one second
- ArithmeticException – if the duration is too large to be represented as nanos
Returns: a clock that ticks in whole units of the duration, not null
/**
* Obtains a clock that returns instants from the specified clock truncated
* to the nearest occurrence of the specified duration.
* <p>
* This clock will only tick as per the specified duration. Thus, if the duration
* is half a second, the clock will return instants truncated to the half second.
* <p>
* The tick duration must be positive. If it has a part smaller than a whole
* millisecond, then the whole duration must divide into one second without
* leaving a remainder. All normal tick durations will match these criteria,
* including any multiple of hours, minutes, seconds and milliseconds, and
* sensible nanosecond durations, such as 20ns, 250,000ns and 500,000ns.
* <p>
* A duration of zero or one nanosecond would have no truncation effect.
* Passing one of these will return the underlying clock.
* <p>
* Implementations may use a caching strategy for performance reasons.
* As such, it is possible that the start of the requested duration observed
* via this clock will be later than that observed directly via the underlying clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}
* providing that the base clock is.
*
* @param baseClock the base clock to base the ticking clock on, not null
* @param tickDuration the duration of each visible tick, not negative, not null
* @return a clock that ticks in whole units of the duration, not null
* @throws IllegalArgumentException if the duration is negative, or has a
* part smaller than a whole millisecond such that the whole duration is not
* divisible into one second
* @throws ArithmeticException if the duration is too large to be represented as nanos
*/
public static Clock tick(Clock baseClock, Duration tickDuration) {
Objects.requireNonNull(baseClock, "baseClock");
Objects.requireNonNull(tickDuration, "tickDuration");
if (tickDuration.isNegative()) {
throw new IllegalArgumentException("Tick duration must not be negative");
}
long tickNanos = tickDuration.toNanos();
if (tickNanos % 1000_000 == 0) {
// ok, no fraction of millisecond
} else if (1000_000_000 % tickNanos == 0) {
// ok, divides into one second without remainder
} else {
throw new IllegalArgumentException("Invalid tick duration");
}
if (tickNanos <= 1) {
return baseClock;
}
return new TickClock(baseClock, tickNanos);
}
//-----------------------------------------------------------------------
Obtains a clock that always returns the same instant.
This clock simply returns the specified instant.
As such, it is not a clock in the conventional sense.
The main use case for this is in testing, where the fixed clock ensures
tests are not dependent on the current clock.
The returned implementation is immutable, thread-safe and Serializable.
Params: - fixedInstant – the instant to use as the clock, not null
- zone – the time-zone to use to convert the instant to date-time, not null
Returns: a clock that always returns the same instant, not null
/**
* Obtains a clock that always returns the same instant.
* <p>
* This clock simply returns the specified instant.
* As such, it is not a clock in the conventional sense.
* The main use case for this is in testing, where the fixed clock ensures
* tests are not dependent on the current clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}.
*
* @param fixedInstant the instant to use as the clock, not null
* @param zone the time-zone to use to convert the instant to date-time, not null
* @return a clock that always returns the same instant, not null
*/
public static Clock fixed(Instant fixedInstant, ZoneId zone) {
Objects.requireNonNull(fixedInstant, "fixedInstant");
Objects.requireNonNull(zone, "zone");
return new FixedClock(fixedInstant, zone);
}
//-------------------------------------------------------------------------
Obtains a clock that returns instants from the specified clock with the
specified duration added
This clock wraps another clock, returning instants that are later by the
specified duration. If the duration is negative, the instants will be
earlier than the current date and time.
The main use case for this is to simulate running in the future or in the past.
A duration of zero would have no offsetting effect.
Passing zero will return the underlying clock.
The returned implementation is immutable, thread-safe and Serializable providing that the base clock is.
Params: - baseClock – the base clock to add the duration to, not null
- offsetDuration – the duration to add, not null
Returns: a clock based on the base clock with the duration added, not null
/**
* Obtains a clock that returns instants from the specified clock with the
* specified duration added
* <p>
* This clock wraps another clock, returning instants that are later by the
* specified duration. If the duration is negative, the instants will be
* earlier than the current date and time.
* The main use case for this is to simulate running in the future or in the past.
* <p>
* A duration of zero would have no offsetting effect.
* Passing zero will return the underlying clock.
* <p>
* The returned implementation is immutable, thread-safe and {@code Serializable}
* providing that the base clock is.
*
* @param baseClock the base clock to add the duration to, not null
* @param offsetDuration the duration to add, not null
* @return a clock based on the base clock with the duration added, not null
*/
public static Clock offset(Clock baseClock, Duration offsetDuration) {
Objects.requireNonNull(baseClock, "baseClock");
Objects.requireNonNull(offsetDuration, "offsetDuration");
if (offsetDuration.equals(Duration.ZERO)) {
return baseClock;
}
return new OffsetClock(baseClock, offsetDuration);
}
//-----------------------------------------------------------------------
Constructor accessible by subclasses.
/**
* Constructor accessible by subclasses.
*/
protected Clock() {
}
//-----------------------------------------------------------------------
Gets the time-zone being used to create dates and times.
A clock will typically obtain the current instant and then convert that
to a date or time using a time-zone. This method returns the time-zone used.
Returns: the time-zone being used to interpret instants, not null
/**
* Gets the time-zone being used to create dates and times.
* <p>
* A clock will typically obtain the current instant and then convert that
* to a date or time using a time-zone. This method returns the time-zone used.
*
* @return the time-zone being used to interpret instants, not null
*/
public abstract ZoneId getZone();
Returns a copy of this clock with a different time-zone.
A clock will typically obtain the current instant and then convert that
to a date or time using a time-zone. This method returns a clock with
similar properties but using a different time-zone.
Params: - zone – the time-zone to change to, not null
Returns: a clock based on this clock with the specified time-zone, not null
/**
* Returns a copy of this clock with a different time-zone.
* <p>
* A clock will typically obtain the current instant and then convert that
* to a date or time using a time-zone. This method returns a clock with
* similar properties but using a different time-zone.
*
* @param zone the time-zone to change to, not null
* @return a clock based on this clock with the specified time-zone, not null
*/
public abstract Clock withZone(ZoneId zone);
//-------------------------------------------------------------------------
Gets the current millisecond instant of the clock.
This returns the millisecond-based instant, measured from 1970-01-01T00:00Z (UTC). This is equivalent to the definition of System.currentTimeMillis().
Most applications should avoid this method and use Instant to represent an instant on the time-line rather than a raw millisecond value. This method is provided to allow the use of the clock in high performance use cases where the creation of an object would be unacceptable.
The default implementation currently calls instant.
Throws: - DateTimeException – if the instant cannot be obtained, not thrown by most implementations
Returns: the current millisecond instant from this clock, measured from
the Java epoch of 1970-01-01T00:00Z (UTC), not null
/**
* Gets the current millisecond instant of the clock.
* <p>
* This returns the millisecond-based instant, measured from 1970-01-01T00:00Z (UTC).
* This is equivalent to the definition of {@link System#currentTimeMillis()}.
* <p>
* Most applications should avoid this method and use {@link Instant} to represent
* an instant on the time-line rather than a raw millisecond value.
* This method is provided to allow the use of the clock in high performance use cases
* where the creation of an object would be unacceptable.
* <p>
* The default implementation currently calls {@link #instant}.
*
* @return the current millisecond instant from this clock, measured from
* the Java epoch of 1970-01-01T00:00Z (UTC), not null
* @throws DateTimeException if the instant cannot be obtained, not thrown by most implementations
*/
public long millis() {
return instant().toEpochMilli();
}
//-----------------------------------------------------------------------
Gets the current instant of the clock.
This returns an instant representing the current instant as defined by the clock.
Throws: - DateTimeException – if the instant cannot be obtained, not thrown by most implementations
Returns: the current instant from this clock, not null
/**
* Gets the current instant of the clock.
* <p>
* This returns an instant representing the current instant as defined by the clock.
*
* @return the current instant from this clock, not null
* @throws DateTimeException if the instant cannot be obtained, not thrown by most implementations
*/
public abstract Instant instant();
//-----------------------------------------------------------------------
Checks if this clock is equal to another clock.
Clocks should override this method to compare equals based on their state and to meet the contract of Object.equals. If not overridden, the behavior is defined by Object.equals
Params: - obj – the object to check, null returns false
Returns: true if this is equal to the other clock
/**
* Checks if this clock is equal to another clock.
* <p>
* Clocks should override this method to compare equals based on
* their state and to meet the contract of {@link Object#equals}.
* If not overridden, the behavior is defined by {@link Object#equals}
*
* @param obj the object to check, null returns false
* @return true if this is equal to the other clock
*/
@Override
public boolean equals(Object obj) {
return super.equals(obj);
}
A hash code for this clock.
Clocks should override this method based on their state and to meet the contract of Object.hashCode. If not overridden, the behavior is defined by Object.hashCode
Returns: a suitable hash code
/**
* A hash code for this clock.
* <p>
* Clocks should override this method based on
* their state and to meet the contract of {@link Object#hashCode}.
* If not overridden, the behavior is defined by {@link Object#hashCode}
*
* @return a suitable hash code
*/
@Override
public int hashCode() {
return super.hashCode();
}
//-----------------------------------------------------------------------
Implementation of a clock that always returns the latest time from System.currentTimeMillis(). /**
* Implementation of a clock that always returns the latest time from
* {@link System#currentTimeMillis()}.
*/
static final class SystemClock extends Clock implements Serializable {
private static final long serialVersionUID = 6740630888130243051L;
private static final long OFFSET_SEED =
System.currentTimeMillis()/1000 - 1024; // initial offest
static final SystemClock UTC = new SystemClock(ZoneOffset.UTC);
private final ZoneId zone;
// We don't actually need a volatile here.
// We don't care if offset is set or read concurrently by multiple
// threads - we just need a value which is 'recent enough' - in other
// words something that has been updated at least once in the last
// 2^32 secs (~136 years). And even if we by chance see an invalid
// offset, the worst that can happen is that we will get a -1 value
// from getNanoTimeAdjustment, forcing us to update the offset
// once again.
private transient long offset;
SystemClock(ZoneId zone) {
this.zone = zone;
this.offset = OFFSET_SEED;
}
@Override
public ZoneId getZone() {
return zone;
}
@Override
public Clock withZone(ZoneId zone) {
if (zone.equals(this.zone)) { // intentional NPE
return this;
}
return new SystemClock(zone);
}
@Override
public long millis() {
// System.currentTimeMillis() and VM.getNanoTimeAdjustment(offset)
// use the same time source - System.currentTimeMillis() simply
// limits the resolution to milliseconds.
// So we take the faster path and call System.currentTimeMillis()
// directly - in order to avoid the performance penalty of
// VM.getNanoTimeAdjustment(offset) which is less efficient.
return System.currentTimeMillis();
}
@Override
public Instant instant() {
// Take a local copy of offset. offset can be updated concurrently
// by other threads (even if we haven't made it volatile) so we will
// work with a local copy.
long localOffset = offset;
long adjustment = VM.getNanoTimeAdjustment(localOffset);
if (adjustment == -1) {
// -1 is a sentinel value returned by VM.getNanoTimeAdjustment
// when the offset it is given is too far off the current UTC
// time. In principle, this should not happen unless the
// JVM has run for more than ~136 years (not likely) or
// someone is fiddling with the system time, or the offset is
// by chance at 1ns in the future (very unlikely).
// We can easily recover from all these conditions by bringing
// back the offset in range and retry.
// bring back the offset in range. We use -1024 to make
// it more unlikely to hit the 1ns in the future condition.
localOffset = System.currentTimeMillis()/1000 - 1024;
// retry
adjustment = VM.getNanoTimeAdjustment(localOffset);
if (adjustment == -1) {
// Should not happen: we just recomputed a new offset.
// It should have fixed the issue.
throw new InternalError("Offset " + localOffset + " is not in range");
} else {
// OK - recovery succeeded. Update the offset for the
// next call...
offset = localOffset;
}
}
return Instant.ofEpochSecond(localOffset, adjustment);
}
@Override
public boolean equals(Object obj) {
if (obj instanceof SystemClock) {
return zone.equals(((SystemClock) obj).zone);
}
return false;
}
@Override
public int hashCode() {
return zone.hashCode() + 1;
}
@Override
public String toString() {
return "SystemClock[" + zone + "]";
}
private void readObject(ObjectInputStream is)
throws IOException, ClassNotFoundException {
// ensure that offset is initialized
is.defaultReadObject();
offset = OFFSET_SEED;
}
}
//-----------------------------------------------------------------------
Implementation of a clock that always returns the same instant.
This is typically used for testing.
/**
* Implementation of a clock that always returns the same instant.
* This is typically used for testing.
*/
static final class FixedClock extends Clock implements Serializable {
private static final long serialVersionUID = 7430389292664866958L;
private final Instant instant;
private final ZoneId zone;
FixedClock(Instant fixedInstant, ZoneId zone) {
this.instant = fixedInstant;
this.zone = zone;
}
@Override
public ZoneId getZone() {
return zone;
}
@Override
public Clock withZone(ZoneId zone) {
if (zone.equals(this.zone)) { // intentional NPE
return this;
}
return new FixedClock(instant, zone);
}
@Override
public long millis() {
return instant.toEpochMilli();
}
@Override
public Instant instant() {
return instant;
}
@Override
public boolean equals(Object obj) {
if (obj instanceof FixedClock) {
FixedClock other = (FixedClock) obj;
return instant.equals(other.instant) && zone.equals(other.zone);
}
return false;
}
@Override
public int hashCode() {
return instant.hashCode() ^ zone.hashCode();
}
@Override
public String toString() {
return "FixedClock[" + instant + "," + zone + "]";
}
}
//-----------------------------------------------------------------------
Implementation of a clock that adds an offset to an underlying clock.
/**
* Implementation of a clock that adds an offset to an underlying clock.
*/
static final class OffsetClock extends Clock implements Serializable {
private static final long serialVersionUID = 2007484719125426256L;
private final Clock baseClock;
private final Duration offset;
OffsetClock(Clock baseClock, Duration offset) {
this.baseClock = baseClock;
this.offset = offset;
}
@Override
public ZoneId getZone() {
return baseClock.getZone();
}
@Override
public Clock withZone(ZoneId zone) {
if (zone.equals(baseClock.getZone())) { // intentional NPE
return this;
}
return new OffsetClock(baseClock.withZone(zone), offset);
}
@Override
public long millis() {
return Math.addExact(baseClock.millis(), offset.toMillis());
}
@Override
public Instant instant() {
return baseClock.instant().plus(offset);
}
@Override
public boolean equals(Object obj) {
if (obj instanceof OffsetClock) {
OffsetClock other = (OffsetClock) obj;
return baseClock.equals(other.baseClock) && offset.equals(other.offset);
}
return false;
}
@Override
public int hashCode() {
return baseClock.hashCode() ^ offset.hashCode();
}
@Override
public String toString() {
return "OffsetClock[" + baseClock + "," + offset + "]";
}
}
//-----------------------------------------------------------------------
Implementation of a clock that adds an offset to an underlying clock.
/**
* Implementation of a clock that adds an offset to an underlying clock.
*/
static final class TickClock extends Clock implements Serializable {
private static final long serialVersionUID = 6504659149906368850L;
private final Clock baseClock;
private final long tickNanos;
TickClock(Clock baseClock, long tickNanos) {
this.baseClock = baseClock;
this.tickNanos = tickNanos;
}
@Override
public ZoneId getZone() {
return baseClock.getZone();
}
@Override
public Clock withZone(ZoneId zone) {
if (zone.equals(baseClock.getZone())) { // intentional NPE
return this;
}
return new TickClock(baseClock.withZone(zone), tickNanos);
}
@Override
public long millis() {
long millis = baseClock.millis();
return millis - Math.floorMod(millis, tickNanos / 1000_000L);
}
@Override
public Instant instant() {
if ((tickNanos % 1000_000) == 0) {
long millis = baseClock.millis();
return Instant.ofEpochMilli(millis - Math.floorMod(millis, tickNanos / 1000_000L));
}
Instant instant = baseClock.instant();
long nanos = instant.getNano();
long adjust = Math.floorMod(nanos, tickNanos);
return instant.minusNanos(adjust);
}
@Override
public boolean equals(Object obj) {
if (obj instanceof TickClock) {
TickClock other = (TickClock) obj;
return baseClock.equals(other.baseClock) && tickNanos == other.tickNanos;
}
return false;
}
@Override
public int hashCode() {
return baseClock.hashCode() ^ ((int) (tickNanos ^ (tickNanos >>> 32)));
}
@Override
public String toString() {
return "TickClock[" + baseClock + "," + Duration.ofNanos(tickNanos) + "]";
}
}
}