TreeSet is an implementation of the SortedSet interface in Java that uses a Tree for storage. The ordering of the elements is maintained by a Set using their natural ordering whether an explicit comparator is provided.
To sort TreeSet 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); } }
Below is the implementation of the above approach:
Example 1:
Java
// 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);
}
} |
Output
Sort elements in ascending order : [ 100, 200, 300, 400, 500]
Example 2:
Java
// 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);
}
} |
Output
Sort elements in descending order : [ 500, 400, 300, 200, 100]