Question

I was wondering if calculating a method’s execution time this way is accurate:

public class GetExecutionTimes {

  public static void main(String args[]) {
    long startTime = System.currentTimeMillis();
    GetExecutionTimes ext = new GetExecutionTimes();
    ext.callMethod();
    long endTime = System.currentTimeMillis();
    System.out.println("Total elapsed time in execution of"
        + " method callMethod() is :" + (endTime - startTime));
  }

  public void callMethod() {
    System.out.println("Calling method");
    for (int i = 1; i <= 10; i++) {
      System.out.println("Value of counter is " + i);
    }
  }
}

More specifically: Will the time difference be the same if I execute in different conditions?

If not how can I make this calculate more precise?

Answer 1

There are several aspects of Java that make writing micro-benchmarks difficult. Garbage collection and just-in-time compilation are two of them.

I would suggest the following as a very good starting point: How do I write a correct micro-benchmark in Java?