@GwtCompatible(emulated=true) public final class Stopwatch extends 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 = Stopwatch.createStarted();
doSomething();
stopwatch.stop(); // optional
Duration duration = stopwatch.elapsed();
log.info("time: " + 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 createUnstarted(Ticker)
or createStarted(Ticker)
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.
Warning for Android users: a stopwatch with default behavior may not continue to keep time while the device is asleep. Instead, create one like this:
Stopwatch.createStarted(
new Ticker() {
public long read() {
return android.os.SystemClock.elapsedRealtimeNanos();
}
});
Modifier and Type | Method and Description |
---|---|
static Stopwatch |
createStarted()
Creates (and starts) a new stopwatch using
System.nanoTime() as its time source. |
static Stopwatch |
createStarted(Ticker ticker)
Creates (and starts) a new stopwatch, using the specified time source.
|
static Stopwatch |
createUnstarted()
Creates (but does not start) a new stopwatch using
System.nanoTime() as its time source. |
static Stopwatch |
createUnstarted(Ticker ticker)
Creates (but does not start) a new stopwatch, using the specified time source.
|
Duration |
elapsed()
Returns the current elapsed time shown on this stopwatch as a
Duration . |
long |
elapsed(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.
|
String |
toString()
Returns a string representation of the current elapsed time.
|
public static Stopwatch createUnstarted()
System.nanoTime()
as its time source.public static Stopwatch createUnstarted(Ticker ticker)
public static Stopwatch createStarted()
System.nanoTime()
as its time source.public static Stopwatch createStarted(Ticker ticker)
public boolean isRunning()
@CanIgnoreReturnValue public Stopwatch start()
Stopwatch
instanceIllegalStateException
- if the stopwatch is already running.@CanIgnoreReturnValue public Stopwatch stop()
Stopwatch
instanceIllegalStateException
- if the stopwatch is already stopped.@CanIgnoreReturnValue public Stopwatch reset()
Stopwatch
instancepublic long elapsed(TimeUnit desiredUnit)
Note: the overhead of measurement can be more than a microsecond, so it is generally
not useful to specify TimeUnit.NANOSECONDS
precision here.
It is generally not a good idea to use an ambiguous, unitless long
to represent
elapsed time. Therefore, we recommend using elapsed()
instead, which returns a
strongly-typed Duration
instance.
elapsedTime()
)@GwtIncompatible public Duration elapsed()
Duration
. Unlike elapsed(TimeUnit)
, this method does not lose any precision due to rounding.Copyright © 2010–2019. All rights reserved.