* Returns the current value of the most precise available system
* timer, in nanoseconds.
* <p>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<sup>63</sup>
* nanoseconds) will not accurately compute elapsed time due to
* numerical overflow.
* <p> For example, to measure how long some code takes to execute:
* <pre>
* long startTime = System.nanoTime();
* // … the code being measured …
* long estimatedTime = System.nanoTime() – startTime;
* </pre>
* @return The current value of the system timer, in nanoseconds.
* @since 1.5





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