In Java, what is the fastest way to get the system time?

System.currentTimeMillis() is fastest as per below test case

public class ClassTest
{
    @Test
    public void testSystemCurrentTime()
    {
        final Stopwatch stopwatch = Stopwatch.createStarted();
        for (int i = 0; i < 1_00_000; i++)
        {
            System.currentTimeMillis();
        }
        stopwatch.stop();
        System.out.println("System.currentTimeMillis(): " + stopwatch);
    }

    @Test
    public void testDateTime()
    {
        final Stopwatch stopwatch = Stopwatch.createStarted();
        for (int i = 0; i < 1_00_000; i++)
        {
            (new Date()).getTime();
        }
        stopwatch.stop();
        System.out.println("(new Date()).getTime(): " + stopwatch);
    }

    @Test
    public void testCalendarTime()
    {
        final Stopwatch stopwatch = Stopwatch.createStarted();
        for (int i = 0; i < 1_00_000; i++)
        {
            Calendar.getInstance().getTimeInMillis();
        }
        stopwatch.stop();
        System.out.println("Calendar.getInstance().getTimeInMillis(): " + stopwatch);
    }

    @Test
    public void testInstantNow()
    {
        final Stopwatch stopwatch = Stopwatch.createStarted();
        for (int i = 0; i < 1_00_000; i++)
        {
            Instant.now();
        }
        stopwatch.stop();
        System.out.println("Instant.now(): " + stopwatch);
    }
}

Output:

(new Date()).getTime(): 36.89 ms
Calendar.getInstance().getTimeInMillis(): 448.0 ms
Instant.now(): 34.13 ms
System.currentTimeMillis(): 10.28 ms

But,

Instant.now() is fast + simpler and provides other utility as well like Instant.now().getEpochSecond();,Instant.now().getNano();, Instant.now().compareTo(otherInstant); and many more.

System.currentTimeMillis()
"Returns the current time in milliseconds".
Use this to get the actual system time.

System.nanoTime().
"The value returned represents nanoseconds since some fixed but arbitrary origin time"
Use this is you're measuring time lapses / events.