HackerRank Java Sort problem solution

In this HackerRank java sort problem in a java programming language, You are given a list of student information: ID, FirstName, and CGPA. Your task is to rearrange them according to their CGPA in decreasing order. If two students have the same CGPA, then arrange them according to their first name in alphabetical order. If those two students also have the same first name, then order them according to their ID. No two students have the same ID.

HackerRank Java Sort problem solution.

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--;
      }
      
      Collections.sort(studentList,new Comparator<Student>(){
        public int compare(Student s1, Student s2){
            if((s1.getCgpa()*100) != (s2.getCgpa()*100)){
                return (int)((s2.getCgpa()*1000) - (s1.getCgpa()*1000));
            }
            else if(!(s1.getFname().equals(s2.getFname()))){
                return s1.getFname().compareTo(s2.getFname());
            }
            else{
                return s1.getId()-s2.getId();
            }
        }
      });    
      
      for(Student st: studentList){
         System.out.println(st.getFname());
      }
   }
}

Second solution

import java.util.*;

class CustomComparator implements Comparator<Student> {
    @Override
    public int compare(Student s1, Student s2) {
        if (s1.getCgpa() < s2.getCgpa()) return 1;
        if (s1.getCgpa() > s2.getCgpa()) return -1;
        
        if (s1.getFname() != s2.getFname()){
            return s1.getFname().compareTo(s2.getFname());
        }
        return s1.getId() - s2.getId();
    }
}

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--;
      }
       
      Collections.sort(studentList, new CustomComparator());
      
      for(Student st: studentList){
          System.out.println(st.getFname());
      }
   }
}

The solution in java8 programming.

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--;
        }
            studentList.sort(new Comparator<Student>(){
                @Override
                public int compare(Student s1,Student s2){
                    if(s1.getCgpa()==s2.getCgpa()){
                        return s1.getFname().compareTo(s2.getFname());

                    }else if(s1.getCgpa()<s2.getCgpa()){
                        return 1;
                    }
                    else{
                        return -1;
                        }
                }
            });

      
          for(Student st: studentList){
            System.out.println(st.getFname());
        }
    }
}