How to Avoid Duplicate User Defined Objects in TreeSet in Java?

// Java Program to Avoid Duplicate User
// Defined Objects in TreeSet
import java.util.*;

// implementing comparable interface
public class Student implements Comparable<Student> {

    private String name;
    private int rank;

    // constructor
    Student(String name, int rank)
    {
        this.name = name;
        this.rank = rank;
    }

    // returns the student name
    private String getName() { return name; }

    // returns student rank
    public int getRank() { return rank; }

    /*
      overriding compareTo() method.
      if the object has same rank then it is considered as a
      duplicate entry, else, the entry is sorted on the
      basis of the student name.
    */
    @Override public int compareTo(Student o)
    {
        if (rank == o.getRank()) {
            return 0;
        }
        else if (name.compareTo(o.getName()) < 0) {
            return -1;
        }
        else
            return 1;
    }

    // overriding toString() to print the student detail
    @Override public String toString()
    {
        return name + " (" + rank + ")";
    }
}

// driver class
class Gfg {
  
    public static void main(String args[])
    {

        // create a TreeSet which stores objects of type
        // Student
        TreeSet<Student> students = new TreeSet<>();
      
        // add objects to the TreeSet
        students.add(new Student("Raghav", 12));
        students.add(new Student("Tilak", 11));
      
        // adding an object with same rank
        students.add(new Student("Ayush", 12));
      
        // adding an object with same name but different
        // rank
        students.add(new Student("Raghav", 32));
      
        // print the TreeSet
        for (Student s : students) {
            System.out.println(s);
        }
    }
}

// Java Program to Avoid Duplicate User
// Defined Objects in TreeSet
import java.util.*;

// implementing comparator interface
public class Employee implements Comparator<Employee> {

    private String name;
    private int id;

    // constructor
    public Employee(String name, int id)
    {
        this.name = name;
        this.id = id;
    }

    // default constructor is required, since we have to
    // pass the instance of Comparator in the constructor,
    // while creating a TreeSet
    public Employee() {}

    // returns employee name
    public String getName() { return name; }

    // returns id of the employee
    public int getId() { return id; }

    /*
     overriding the compare() method, this method compare
     two objects of type Employee on the basis of their id,
     if the ids of two employees is same then its considered
     a duplicate entry. else, it is sorted of the basis of
     id.
    */
    @Override
    public int compare(Employee emp1, Employee emp2)
    {
        if (emp1.getId() == emp2.getId()) {
            return 0;
        }
        else if (emp1.getId() < emp2.getId()) {
            return -1;
        }
        else {
            return 1;
        }
    }

    // overriding toString() to print the employee detail
    @Override public String toString()
    {
        return name + " (" + id + ")";
    }
}
// driver class
class Gfg {
    public static void main(String args[])
    {

        // create a TreeSet which stores objects of type
        // Employee
        TreeSet<Employee> employees
            = new TreeSet<>(new Employee());
      
        // add objects to the TreeSet
        employees.add(new Employee("Raghav", 934));
        employees.add(new Employee("Tilak", 435));
        employees.add(new Employee("Mumukshi", 252));
      
        // adding an object with same id
        employees.add(new Employee("Shalu", 934));

        // printing the TreeSet
        for (Employee s : employees) {
            System.out.println(s);
        }
    }
}