Collections.sort(studentList,new Comparator<Student>(){
                public int compare(Student s1,Student s2){
                int[] res = {Double.compare(s2.getCgpa(),
                s1.getCgpa()),s1.getFname().compareTo(s2.getFname()),
                Integer.compare(s1.getId(), s2.getId())};
                for (int r : res){if (r != 0){return r;}}
                return 0 ; 
                }
        });