How can I count the time it takes a function to co

Question

I need to measure the time it takes for a function to complete in Java. How can I do that?

Note:

I want to measure the function's time consumption, not that of the full program.

Answer 1

Here is how can compute the elapsed time.

// Get current time
long start = System.currentTimeMillis();

// Do something ...

// Get elapsed time in milliseconds
long elapsedTimeMillis = System.currentTimeMillis()-start;

// Get elapsed time in seconds
float elapsedTimeSec = elapsedTimeMillis/1000F;

// Get elapsed time in minutes
float elapsedTimeMin = elapsedTimeMillis/(60*1000F);

// Get elapsed time in hours
float elapsedTimeHour = elapsedTimeMillis/(60*60*1000F);

// Get elapsed time in days
float elapsedTimeDay = elapsedTimeMillis/(24*60*60*1000F);

Answer 2

Use a profiler.

Answer 3

System.nanoTime should be used to accurately measure the delta between two times for microbenchmarks.

public class CountTime {

  private static void walk() {
    for (int i = 0; i < Integer.MAX_VALUE; i++)
      ;
  }

  public static void main(String[] args) {
    long t0 = System.nanoTime();
    walk();
    long t1 = System.nanoTime();
    System.out.println("Elapsed time =" + (t1 - t0)
        + " nanoseconds");
  }

}

System.currentTimeMillis returns the current time in milliseconds. You can use this to get the current time. This may be useful on older VMs or for longer running processes.

Answer 4

this analogue stopwatch is another option for us too... Check on Java2s.com here.