How to Sort LinkedHashSet Elements using Comparable Interface in Java?
Last Updated :
04 Oct, 2021
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The LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all elements. When the iteration order is needed to be maintained this class is used. When iterating through a HashSet the order is unpredictable, while a LinkedHashSet lets us iterate through the elements in the order in which they were inserted.
To sort LinkedHashSet 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.
// 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);
Example 1
// Java program demonstrate how to Sort LinkedHashSet 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 LinkedHashSet in
// ascending order
public int compareTo(Student stu)
{
return this.marks.compareTo(stu.marks);
}
}
class GFG {
public static void main(String[] args)
{
// New LinkedHashSet
LinkedHashSet<Student> set = new LinkedHashSet<>();
// 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 ascending order : "
+ set);
// TreeSet to sort LinkedHashSet using comparable
TreeSet<Student> tree_set = new TreeSet<>(set);
// Print after sorting
System.out.println(
"After sort elements in ascending order : "
+ tree_set);
}
}
Output
Before sort elements in ascending order : [ 500, 300, 400, 100, 200] After sort elements in ascending order : [ 100, 200, 300, 400, 500]
Example 2
// Java program demonstrate how to Sort LinkedHashSet 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 LinkedHashSet in
// descending order
public int compareTo(Student stu)
{
return stu.marks.compareTo(this.marks);
}
}
class GFG {
public static void main(String[] args)
{
// New LinkedHashSet
LinkedHashSet<Student> set = new LinkedHashSet<>();
// 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 LinkedHashSet using comparable
TreeSet<Student> tree_set = new TreeSet<>(set);
// Print after sorting
System.out.println(
"After sort elements in descending order : "
+ tree_set);
}
}
Output:
Before sort elements in descending order : [ 500, 300, 400, 100, 200] After sort elements in descending order : [ 500, 400, 300, 200, 100]
