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8069269: (spec) Defect in the System.nanoTime spec

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Change the description of how to compare two nanoTime values.

Reviewed-by: martin
This commit is contained in:
Brian Burkhalter 2015-01-26 17:16:57 -08:00
parent d58ef60b88
commit 3e68a8af37
1 changed files with 7 additions and 10 deletions
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17
jdk/src/java.base/share/classes/java/lang/System.java
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@ -376,19 +376,16 @@ public final class System {
* the difference between two such values, obtained within the same
* instance of a Java virtual machine, is computed.
*
* <p> For example, to measure how long some code takes to execute:
* <pre> {@code
* <p>For example, to measure how long some code takes to execute:
* <pre> {@code
* long startTime = System.nanoTime();
* // ... the code being measured ...
* long estimatedTime = System.nanoTime() - startTime;}</pre>
* long elapsedNanos = System.nanoTime() - startTime;}</pre>
*
* <p>To compare two nanoTime values
* <pre> {@code
* long t0 = System.nanoTime();
* ...
* long t1 = System.nanoTime();}</pre>
*
* one should use {@code t1 - t0 < 0}, not {@code t1 < t0},
* <p>To compare elapsed time against a timeout, use <pre> {@code
* if (System.nanoTime() - startTime >= timeoutNanos) ...}</pre>
* instead of <pre> {@code
* if (System.nanoTime() >= startTime + timeoutNanos) ...}</pre>
* because of the possibility of numerical overflow.
*
* @return the current value of the running Java Virtual Machine's