How to measure the time taken by a function in Java?

java.lang.System.currentTimeMillis() method can be used to compute the time taken by a function in java. Trick is simple. Get the before time and after time using currentTimeMillis() where before time is the time when method is invoked and after time is when method has executed. See the example below −

Example

 Live Demo

public class Tester{
   public static void main(String[] args) {
      long startTime = System.currentTimeMillis();
      longRunningMethod();
      long endTime = System.currentTimeMillis();
      System.out.println("Time taken: " + (endTime -startTime) + " ms");
   }

   private static void longRunningMethod() {
      try {
         Thread.sleep(1000);
      } catch (InterruptedException e) {
         e.printStackTrace();
      }
   }
}

Output

Time taken: 1000 ms