Created
July 26, 2011 19:55
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Stopwatch: Record real time taken for an operation, across multiple runs
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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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