How to Sort LinkedHashSet Elements using Comparable Interface in Java?

Last Updated : 04 Oct, 2021

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

// Java program demonstrate how to Sort LinkedHashSet using
// Comparable interface
importjava.util.*;
 
// Student class implements comparable interface
classStudent implementsComparable<Student> {
    Integer marks;
 
    Student(Integer marks) { this.marks = marks; }
 
    // override toString method
    publicString toString() { return(" "+ this.marks); }
 
    // Override compareTo method to sort LinkedHashSet in
    // ascending order
    publicintcompareTo(Student stu)
    {
        returnthis.marks.compareTo(stu.marks);
    }
}
 
classGFG {
    publicstaticvoidmain(String[] args)
    {
 
        // New LinkedHashSet
        LinkedHashSet<Student> set = newLinkedHashSet<>();
 
        // Adding elements to the set
        set.add(newStudent(500));
        set.add(newStudent(300));
        set.add(newStudent(400));
        set.add(newStudent(100));
        set.add(newStudent(200));
 
        // Print Before sort
        System.out.println(
            "Before sort elements in ascending order : "
            + set);
 
        // TreeSet to sort LinkedHashSet using comparable
        TreeSet<Student> tree_set = newTreeSet<>(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

// Java program demonstrate how to Sort LinkedHashSet using
// Comparable interface
importjava.util.*;
 
// Student class implements comparable interface
classStudent implementsComparable<Student> {
    Integer marks;
 
    Student(Integer marks) { this.marks = marks; }
 
    // override toString method
    publicString toString() { return(" "+ this.marks); }
 
    // Override compareTo method to sort LinkedHashSet in
    // descending order
    publicintcompareTo(Student stu)
    {
        returnstu.marks.compareTo(this.marks);
    }
}
 
classGFG {
    publicstaticvoidmain(String[] args)
    {
 
        // New LinkedHashSet
        LinkedHashSet<Student> set = newLinkedHashSet<>();
 
        // Adding elements to the set
        set.add(newStudent(500));
        set.add(newStudent(300));
        set.add(newStudent(400));
        set.add(newStudent(100));
        set.add(newStudent(200));
 
        // Print Before sort
        System.out.println(
            "Before sort elements in descending order : "
            + set);
 
        // TreeSet to sort LinkedHashSet using comparable
        TreeSet<Student> tree_set = newTreeSet<>(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]

Java 8 Optional Class

KapilChhipa

Improve

Article Tags :

Practice Tags :

Java

How to Sort LinkedHashSet Elements using Comparable Interface in Java?

Java

Java

Similar Reads

Lambda Expressions

Functional Interfaces

Method Reference

Streams

Java Stream Programs

Java Stream Methods

Comparable and Comparator

Optional Class

Date/Time API

Thank You!

What kind of Experience do you want to share?