InstantSource
public
interface
InstantSource
| java.time.InstantSource |
Provides access to the current instant.
Instances of this interface are used to access a pluggable representation of the current instant.
For example, InstantSource can be used instead of System#currentTimeMillis().
The primary purpose of this abstraction is to allow alternate instant sources 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.
As such, this interface does not guarantee the result actually represents the current instant on the time-line. Instead, it allows the application to provide a controlled view as to what the current instant is.
Best practice for applications is to pass an InstantSource into any method
that requires the current instant. A dependency injection framework is one
way to achieve this:
public class MyBean {
private InstantSource source; // dependency inject
...
public void process(Instant endInstant) {
if (source.instant().isAfter(endInstant) {
...
}
}
}
This approach allows an alternative source, such as fixed
or offset to be used during testing.
The system factory method provides a source based on the best available
system clock. This may use System#currentTimeMillis(), or a higher
resolution clock if one is available.
Summary
Public methods | |
|---|---|
static
InstantSource
|
fixed(Instant fixedInstant)
Obtains a source that always returns the same instant. |
abstract
Instant
|
instant()
Gets the current instant of the source. |
default
long
|
millis()
Gets the current millisecond instant of the source. |
static
InstantSource
|
offset(InstantSource baseSource, Duration offsetDuration)
Obtains a source that returns instants from the specified source with the specified duration added. |
static
InstantSource
|
system()
Obtains a source that returns the current instant using the best available system clock. |
static
InstantSource
|
tick(InstantSource baseSource, Duration tickDuration)
Obtains a source that returns instants from the specified source truncated to the nearest occurrence of the specified duration. |
default
Clock
|
withZone(ZoneId zone)
Returns a clock with the specified time-zone. |
Public methods
fixed
public static InstantSource fixed (Instant fixedInstant)
Obtains a source that always returns the same instant.
This source simply returns the specified instant. As such, it is not a source that represents the current instant. The main use case for this is in testing, where the fixed source ensures tests are not dependent on the current source.
The returned implementation is immutable, thread-safe and Serializable.
| Parameters | |
|---|---|
fixedInstant |
Instant: the instant to use, not null |
| Returns | |
|---|---|
InstantSource |
a source that always returns the same instant, not null |
instant
public abstract Instant instant ()
Gets the current instant of the source.
This returns an instant representing the current instant as defined by the source.
| Returns | |
|---|---|
Instant |
the current instant from this source, not null |
| Throws | |
|---|---|
DateTimeException |
if the instant cannot be obtained, not thrown by most implementations |
millis
public long millis ()
Gets the current millisecond instant of the source.
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 source in high performance use cases
where the creation of an object would be unacceptable.
Implementation Requirements:
- The default implementation calls
instant().
| Returns | |
|---|---|
long |
the current millisecond instant from this source, 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 |
offset
public static InstantSource offset (InstantSource baseSource, Duration offsetDuration)
Obtains a source that returns instants from the specified source with the specified duration added.
This source wraps another source, 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 source.
The returned implementation is immutable, thread-safe and Serializable
providing that the base source is.
| Parameters | |
|---|---|
baseSource |
InstantSource: the base source to add the duration to, not null |
offsetDuration |
Duration: the duration to add, not null |
| Returns | |
|---|---|
InstantSource |
a source based on the base source with the duration added, not null |
system
public static InstantSource system ()
Obtains a source that returns the current instant using the best available system clock.
This source is based on the best available system clock. This may use
System#currentTimeMillis(), or a higher resolution system clock if
one is available.
The returned implementation is immutable, thread-safe and
Serializable.
| Returns | |
|---|---|
InstantSource |
a source that uses the best available system clock, not null |
tick
public static InstantSource tick (InstantSource baseSource, Duration tickDuration)
Obtains a source that returns instants from the specified source truncated to the nearest occurrence of the specified duration.
This source will only tick as per the specified duration. Thus, if the duration is half a second, the source 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 source.
Implementations may use a caching strategy for performance reasons. As such, it is possible that the start of the requested duration observed via this source will be later than that observed directly via the underlying source.
The returned implementation is immutable, thread-safe and
Serializable providing that the base source is.
| Parameters | |
|---|---|
baseSource |
InstantSource: the base source to base the ticking source on, not null |
tickDuration |
Duration: the duration of each visible tick, not negative, not null |
| Returns | |
|---|---|
InstantSource |
a source 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 |
ArithmeticException |
if the duration is too large to be represented as nanos |
withZone
public Clock withZone (ZoneId zone)
Returns a clock with the specified time-zone.
This returns a Clock, which is an extension of this interface
that combines this source and the specified time-zone.
The returned implementation is immutable, thread-safe and Serializable
providing that this source is.
Implementation Requirements:
- The default implementation returns an immutable, thread-safe and
Serializablesubclass ofClockthat combines this source and the specified zone.
| Parameters | |
|---|---|
zone |
ZoneId: the time-zone to use, not null |
| Returns | |
|---|---|
Clock |
a clock based on this source with the specified time-zone, not null |