in response to https://gist.github.com/mccutchen/831a1da33e1f8c74f994

SortTest.java

import java.util.Arrays;
import java.util.Comparator;

class EvenFirst implements Comparator<Integer> {
    public int compare(Integer a, Integer b) {
        return a % 2 - b % 2;
    }
}

public class SortTest {

    static void sortTest() {
        Integer[] xs = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        // Sort those Integer objects
        Arrays.sort(xs, new EvenFirst());

        Integer[] expected = {2, 4, 6, 8, 10, 1, 3, 5, 7, 9};
        System.out.println("Got expected results? " + Arrays.equals(xs, expected));
    }

    public static void main(String[] args) {
        sortTest();
    }
}

auto-boxing and auto-unboxing