public class CarsSet implements Comparable {
    String mark;

    public CarsSet(String mark) {
        this.mark = mark;

    }
    @Override
    public int compareTo(Object obj) {
        CarsSet entry = (CarsSet) obj;
        int result = mark.compareTo(entry.mark);

        if (result != 0) {
            return result;
        }
        return 0;
    }





}



public class Cars {
    public static void main(String [] args) {

        TreeSet<CarsSet> cs = new TreeSet<CarsSet>();
        cs.add(new CarsSet("BMW"));
        cs.add(new CarsSet("Audi"));
        cs.add(new CarsSet("Subaru"));
//        String sortType = args[0];

        for(CarsSet c: cs) {

            System.out.println("Mark:" + c.mark);
        }

    }

}