TeenageSorterVersion2.java

public class TeenageSorter implements Comparator<Teenager>{
    @Override
    public int compare(Teenager t1, Teenager t2) {
        if( t1.getAge() == t2.getAge()){
            return sortByPhoneBrand(t1.getPhoneBrand(),t2.getPhoneBrand());
        }           
        return t1.getAge() > t2.getAge()? 1 : -1;
    }
    
    private int sortByPhoneBrand(String phoneBrand1,String phoneBrand2){
        if(phoneBrand1 == null && phoneBrand2 == null){
            return 0;
        }
        if(phoneBrand1 == null && phoneBrand2 != null){
            return 1;
        }
        if(phoneBrand1 != null && phoneBrand2 == null){
            return -1;
        }
        return phoneBrand1.compareTo(phoneBrand2);        
    }
}