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@lpar
Created Jul 26, 2011
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Stopwatch: Record real time taken for an operation, across multiple runs
import java.text.DecimalFormat;
/**
* The Stopwatch class provides a simple way to record the real-world time taken by an operation,
* averaged over multiple runs, and report the result easily in logs.
*
* An example use case would be timing JDBC calls to a relational database.
*
* This code does not measure CPU time or pay any attention to whether a thread or process is
* active or not. For that, you need to use a profiler.
*
* @author mathew <meta@pobox.com>
*
* Placed into the public domain.
*/
public class Stopwatch {
private static DecimalFormat format = new DecimalFormat("#.##");
private long tstart;
private long tstop;
private long total = 0;
private int runs = 0;
/**
* Start a new run of timing something.
* If the Stopwatch is already timing something, that existing run is canceled.
*/
public void start() {
tstart = System.nanoTime();
}
/**
* Stop the current timing run.
* Does nothing if no existing run is active.
*/
public void stop() {
if (tstart != 0) {
tstop = System.nanoTime();
total += (tstop - tstart);
runs += 1;
tstart = 0;
}
}
/**
* @return the total number of elapsed seconds recorded by this Stopwatch object in all runs.
*/
public double getTotalSeconds() {
return ((double) total) / 1000000000;
}
/**
* @return the average number of seconds per run recorded by this Stopwatch object.
*/
public double getAverageSeconds() {
if (runs == 0) {
return 0;
}
return ((double) total) / 1000000000 / runs;
}
/**
* @return the number of runs completed.
*/
public int getRuns() {
return runs;
}
/**
* @return a string representation of the Stopwatch object suitable for output to humans.
* e.g. "1.46ms (87 runs)"
*/
@Override
public String toString() {
final double avg = this.getAverageSeconds();
int pow = (int) Math.round(-Math.log10(avg));
double mult;
String unit;
if (pow < 0) {
pow = 0;
}
if (pow < 2) {
unit = "s";
mult = 1.0;
} else if (pow < 4) {
unit = "ms";
mult = 1000.0;
} else if (pow < 7) {
unit = "µs";
mult = 1000000.0;
} else {
unit = "ns";
mult = 1000000000.0;
}
return format.format(mult * avg) + unit + " (" + Integer.toString(runs) + " run" + (runs > 1 ? "s" : "") +")";
}
}
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