com.google.common.base
@Beta @GwtCompatible(emulated=true) public final class Stopwatch extends java.lang.Object
System.nanoTime()
for a few reasons:
nanoTime
, the value returned has no absolute
meaning, and can only be interpreted as relative to another timestamp
returned by nanoTime
at a different time. Stopwatch
is a
more effective abstraction because it exposes only these relative values,
not the absolute ones.
Basic usage:
Stopwatch stopwatch = new Stopwatch().start
(); doSomething(); stopwatch.stop
(); // optional long millis = stopwatch.elapsedMillis
(); log.info("that took: " + stopwatch); // formatted string like "12.3 ms"
Stopwatch methods are not idempotent; it is an error to start or stop a stopwatch that is already in the desired state.
When testing code that uses this class, use the alternate constructor to supply a fake or mock ticker. This allows you to simulate any valid behavior of the stopwatch.
Note: This class is not thread-safe.
Constructor and Description |
---|
Stopwatch()
Creates (but does not start) a new stopwatch using
System.nanoTime()
as its time source. |
Stopwatch(Ticker ticker)
Creates (but does not start) a new stopwatch, using the specified time
source.
|
Modifier and Type | Method and Description |
---|---|
long |
elapsedMillis()
Returns the current elapsed time shown on this stopwatch, expressed
in milliseconds, with any fraction rounded down.
|
long |
elapsedTime(java.util.concurrent.TimeUnit desiredUnit)
Returns the current elapsed time shown on this stopwatch, expressed
in the desired time unit, with any fraction rounded down.
|
boolean |
isRunning()
|
Stopwatch |
reset()
Sets the elapsed time for this stopwatch to zero,
and places it in a stopped state.
|
Stopwatch |
start()
Starts the stopwatch.
|
Stopwatch |
stop()
Stops the stopwatch.
|
java.lang.String |
toString()
Returns a string representation of the current elapsed time; equivalent to
toString(4) (four significant figures). |
java.lang.String |
toString(int significantDigits)
Returns a string representation of the current elapsed time, choosing an
appropriate unit and using the specified number of significant figures.
|
public Stopwatch()
System.nanoTime()
as its time source.public Stopwatch(Ticker ticker)
public boolean isRunning()
public Stopwatch start()
Stopwatch
instancejava.lang.IllegalStateException
- if the stopwatch is already running.public Stopwatch stop()
Stopwatch
instancejava.lang.IllegalStateException
- if the stopwatch is already stopped.public Stopwatch reset()
Stopwatch
instancepublic long elapsedTime(java.util.concurrent.TimeUnit desiredUnit)
Note that the overhead of measurement can be more than a microsecond, so
it is generally not useful to specify TimeUnit.NANOSECONDS
precision here.
public long elapsedMillis()
elapsedTime(TimeUnit.MILLISECONDS
.@GwtIncompatible(value="String.format()") public java.lang.String toString()
toString(4)
(four significant figures).toString
in class java.lang.Object
@GwtIncompatible(value="String.format()") public java.lang.String toString(int significantDigits)
elapsedTime(NANOSECONDS)
would
return {1234567}, toString(4)
returns "1.235 ms"
.