JAVA SORT HACKKERANK WITH COMPARATOR.COMPARING AND THEN COMPARING FUNCTION

 import java.util.*;

class Student{

    private int id;

    private String fname;

    private double cgpa;

    public Student(int id, String fname, double cgpa) {

        super();

        this.id = id;

        this.fname = fname;

        this.cgpa = cgpa;

    }

    public int getId() {

        return id;

    }

    public String getFname() {

        return fname;

    }

    public double getCgpa() {

        return cgpa;

    }

}

//Complete the code

public class Solution

{

    public static void main(String[] args){

        Scanner in = new Scanner(System.in);

        int testCases = Integer.parseInt(in.nextLine());

        

        List<Student> studentList = new ArrayList<Student>();

        while(testCases>0){

            int id = in.nextInt();

            String fname = in.next();

            double cgpa = in.nextDouble();

            

            Student st = new Student(id, fname, cgpa);

            studentList.add(st);

            

            testCases--;

        }/*

       Comparator<Student> compareByCgpa = (Student o1, Student o2) ->

        (int)(o1.getCgpa()-o2.getCgpa());

 

        Collections.sort(studentList, compareByCgpa.reversed());

        

        for(int i=0;i<studentList.size()-1;i++){

           if((studentList.get(i)).getCgpa()==(studentList.get(i+1)).getCgpa()){

                  if(String.valueOf(studentList.get(i).getFname()).

                  compareTo(String.valueOf(studentList.get(i+1) .getFname()))>0){

                      String temp1=String.valueOf(studentList.get(i).getFname());

                      String temp2=String.valueOf(studentList.get(i+1).getFname());

                      String temp3;

                      temp3=temp1;

                      temp1=temp2;

                      temp2=temp3;

                  }  

                  else if(String.valueOf(studentList.get(i).getFname()).

                  compareTo(String.valueOf(studentList.get(i+1).getFname()))==0){

                      if((studentList.get(i).getId()-studentList.get(i+1).getId())>0){

                          int temp1=studentList.get(i).getId();

                          int temp2=studentList.get(i+1).getId();;

                          int temp3;

                          temp3=temp1;

                          temp1=temp2;

                          temp2=temp3;

                      }

                  }    

            }

        }

                */

     Collections.sort(studentList, Comparator.comparing(Student :: getCgpa).reversed().thenComparing(Student :: getFname).thenComparing(Student :: getId));

         

        

        for(Student st: studentList){

            System.out.println(st.getFname());

        }

    }

}