How to Sort HashSet Elements using Comparable Interface in Java?

The HashSet class implements the Set interface, backed by a hash table which is actually a HashMap instance. No guarantee is made as to the iteration order of the set which means when we iterate the HashSet, there is no guarantee that we get elements in which order they were inserted.

To sort HashSet elements using Comparable interface in java first, we create a class Student that implements the Comparable interface. In this class we override the compareTo() method.

Pseudo Code:

// 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);
 }
}

And then we pass the set to the TreeSet constructor to sort the elements.

// TreeSet to sort LinkedHashSet using comparable

TreeSet<Student> tree_set = new TreeSet<>(set);

Below is the full implementation of the above approach:

Example 1:

Before sort elements in ascending order : [ 300, 400, 500, 200, 100]
After sort elements in ascending order : [ 100, 200, 300, 400, 500]

Example 2: