How to measure the a time-span in seconds using System.currentTimeMillis()?
Solution 1:
TimeUnit
Use the TimeUnit
enum built into Java 5 and later.
long timeMillis = System.currentTimeMillis();
long timeSeconds = TimeUnit.MILLISECONDS.toSeconds(timeMillis);
Solution 2:
long start = System.currentTimeMillis();
counter.countPrimes(1000000);
long end = System.currentTimeMillis();
System.out.println("Took : " + ((end - start) / 1000));
UPDATE
An even more accurate solution would be:
final long start = System.nanoTime();
counter.countPrimes(1000000);
final long end = System.nanoTime();
System.out.println("Took: " + ((end - start) / 1000000) + "ms");
System.out.println("Took: " + (end - start)/ 1000000000 + " seconds");