Something like this :)

     long startTime = System.currentTimeMillis();
        for(int i =0; i<10000000;i++){
            Kata.findEvenIndex(new int[]{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20});
        }
        long endTime = System.currentTimeMillis();
        System.out.println("That took " + (endTime - startTime) + " milliseconds (or " + (endTime - startTime)/1000 + " seconds)");

How are you testing the speed? What about my solution? :D

Too many loops. IntStream.of and Arrays.copyOfRange and sum are alle loops.
Took 26052 ms to run for 10000000 runs

Too many loops. try doing it with two. Took 2100 ms for 10000000 runs

Very slow. Took 47403 ms for 10000000 runs.

Good for readability. Took 2300 ms for 10000000 runs

Clever. Takes about 1400ms to run for 10000000 runs