public class Main {

    public static void main(String[] args) throws Exception {

        MyEnum[] e = new MyEnum[] { A, C, D, B }; // 1, 3, 4, 2
        Arrays.sort(e, new EnumComparator());
        System.out.println(Arrays.toString(e)); // [1, 2, 3, 4]

    }
}

class EnumComparator implements Comparator<MyEnum> {

    @Override
    public int compare(MyEnum o1, MyEnum o2) {
        return o1.toString().compareTo(o2.toString());
    }

}

enum MyEnum {

    D("4"),
    A("1"),
    B("2"),
    C("3");

    private String index;

    private MyEnum(String index) {
        this.index = index;
    }

    @Override
    public String toString() {
        return index;
    }

}