How to Sort LinkedHashSet Elements using Comparable Interface in Java?
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 interfaceimport java.util.*;// Student class implements comparable interfaceclass 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
// Java program demonstrate how to Sort LinkedHashSet using// Comparable interfaceimport java.util.*;// Student class implements comparable interfaceclass 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]
