TeenageSorterGuava.java

Collections.sort(teens,new Comparator<Teenager>() {
            @Override
            public int compare(Teenager t1, Teenager t2) 
            {               
               return 
                    ComparisonChain.start()
                                   .compare(t1.getAge(), t2.getAge())
                                   .compare(t1.getPhoneBrand(), t2.getPhoneBrand(),Ordering.natural().nullsLast())
                                   .result();
            }
        });