Simple and complex! Your solution open my mind to study streams, u rock dude!

It was already mentioned below 2 and 5 years ago, isn't it? Updated Java tests, now this solution is invalid.

The code doesn't work in this test:

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class SolutionTest {

@Test
public void simpleArray1() {
    assertEquals(2, getActualFor(1, 2, 1, 1, 1 , 1 ,1 ,1));
}

private int getActualFor(int... numbers) {
    return Solution.stray(numbers);
}

}