¿Cómo ordenar los elementos de TreeSet usando una interfaz comparable en Java?

TreeSet es una implementación de la interfaz SortedSet en Java que utiliza un árbol para el almacenamiento. El orden de los elementos se mantiene mediante un Conjunto utilizando su orden natural si se proporciona un comparador explícito.

Para ordenar los elementos de TreeSet usando la interfaz Comparable en Java primero, creamos una clase Student que implementa la interfaz Comparable. En esta clase anulamos el método compareTo() .

Pseudocódigo:

// 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 LinkedHashSet in ascending order
    public int compareTo(Student stu) {
        return this.marks.compareTo(stu.marks);
    }
}

A continuación se muestra la implementación del enfoque anterior:

Ejemplo 1:

// Java program to demonstrate how to Sort TreeSet using
// Comparable interface in ascending order
 
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 TreeSet in
    // ascending order
    public int compareTo(Student stu)
    {
        return this.marks.compareTo(stu.marks);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New TreeSet
        TreeSet<Student> set = new TreeSet<>();
 
        // 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 TreeSet sorted in ascending order
        System.out.println("Sort elements in ascending order : " + set);
       
    }
}

Sort elements in ascending order : [ 100,  200,  300,  400,  500]

Ejemplo 2: 

// Java program demonstrate how to Sort TreeSet using
// Comparable interface in descending order
 
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 TreeSet in
    // descending order
    public int compareTo(Student stu)
    {
        return stu.marks.compareTo(this.marks);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New TreeSet
        TreeSet<Student> set = new TreeSet<>();
 
        // 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 TreeSet sorted in descending order
        System.out.println("Sort elements in descending order : " + set);
       
    }
}

Sort elements in descending order : [ 500,  400,  300,  200,  100]