| Returns the current value of the most precise available system timer,
in nanoseconds. This method can only be used to measure elapsed time and
is not related to any other notion of system or wall-clock time. The
value returned represents nanoseconds since some fixed but arbitrary
time (perhaps in the future, so values may be negative). This method
provides nanosecond precision, but not necessarily nanosecond accuracy.
No guarantees are made about how frequently values change. Differences
in successive calls that span greater than approximately 292 years
(2^63 nanoseconds) will not accurately compute elapsed time due to
numerical overflow.
Implementation note:By default, this method uses
sun.misc.Perf on Java 1.4.2, and falls back to
System.currentTimeMillis() emulation on earlier JDKs. Custom
timer can be provided via the system property
edu.emory.mathcs.backport.java.util.concurrent.NanoTimerProvider.
The value of the property should name a class implementing
NanoTimer interface.
Note: on JDK 1.4.2, sun.misc.Perf timer seems to have
resolution of the order of 1 microsecond, measured on Linux.
The current value of the system timer, in nanoseconds. |
