How to measure the time of a process

To measure the time of a process just call the System.nanoTime method when process starts and again when process ends. The time of the process will be the diference betwen the two calls.

package time;

public class Time {

    public static void main(String[] args) {

        long start_time, end_time, elapsedTime;

        start_time = System.nanoTime();

        // ... the code being measured ...

        end_time = System.nanoTime();
        elapsedTime = end_time - start_time;
        
        System.out.println("Start: " + start_time);
        System.out.println("End  : " + end_time);
    ...

The System.nanoTime method returns values in nanoseconds, to convert nanoseconds to miliseconds or seconds you just need to make a few divisions:

     System.out.println("The process took approximately:\n "
                        +elapsedTime+" nano seconds\n " 
                        +(elapsedTime/1000000.0)+" miliseconds\n " 
                        +(elapsedTime/1000000000.0)+" seconds");