CODE EXAMPLE FOR JAVA

Comparable interface

// Java program to demonstrate how to Sort HashSet using
// Comparable interface
 
import java.util.*;
 
// Student class implements comparable interface
class Student implements Comparable<Student> {
   
    Integer marks;
 
    Student(Integer marks) { this.marks = marks; }
 
    // override toString method
    public String toString() { return (" " + this.marks); }
 
    // Override compareTo method to sort HashSet in
    // descending order
    public int compareTo(Student stu)
    {
        return stu.marks.compareTo(this.marks);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New HashSet
        HashSet<Student> set = new HashSet<>();
 
        // Adding elements to the set
        set.add(new Student(500));
        set.add(new Student(300));
        set.add(new Student(400));
        set.add(new Student(100));
        set.add(new Student(200));
 
        // Print Before sort
        System.out.println("Before sort elements in descending order : "
            + set);
 
        // TreeSet to sort HashSet using comparable
        // interface
        TreeSet<Student> tree_set = new TreeSet<>(set);
 
        // Print after sorting
        System.out.println("After sort elements in descending order : "
            + tree_set);
    }
}