How to Implement a Custom Order Sorting for Elements in a LinkedHashSet?

In Java, LinkedHashSet is the implementation is different from the HashSet. HashSet maintains the Doubly-LinkedList across all of its elements of the LinkedHashSet. In LinkedHashSet, it maintains to sort all elements of the object in a List.

In this article, we will learn to implement a custom order or sorting for elements in a LinkedHashSet in Java.

Implementation Process:

• The LinkedHashSet contains unique elements, and it does not directly sort all elements.
• So, we can convert the LinkedHashSet to a List.
• In this List, we can iterate the insertion of sorted elements by using comparator and comparable interface classes.

Syntax to Convert LinkedHashSet to List:

List<String> list = new ArrayList<>( )

Syntax to sort the List using a custom Comparator:

list.sort(new Comparator<String>() {
      @Override
      public int compare(String str1, Strig str2) {
              return Integer.compare(str1.length(), str2.length());
       }
});

Syntax to Convert List back to LinkedHashSet:

LinkedHashSet<String> sortedFruits = new LinkedHashSet<>(list);

Program to Implement a Custom Order or Sorting for elements in a LinkedHashSet in Java

Below are the implementations to Implement a Custom order or Sorting for Elements in a LinkedHashSet.

Approach: By Converting LinkedHashSet to List and then using Sorting

Java

// Java program to implement a custom order or sorting for elements in a LinkedHashSet
// by converting LinkedHashSet to a List and then using sorting
import java.util.ArrayList;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;

public class CustomSortingLinkedHashSet
{
    public static void main(String[] args)
    {
          LinkedHashSet<String> fruits = new LinkedHashSet<String>();

        fruits.add("Kiwi");
        fruits.add("Strawberry");
        fruits.add("Mango");
        fruits.add("Plum");

        System.out.println("Original order:" );
        for (String fruit : fruits) {
            System.out.println(fruit);
        }

        // convert LinkedHashSet to a List
        List<String> list = new ArrayList<>(fruits);

        // sort the List based on custom criteria (length of strings)
        list.sort(new Comparator<String>() {

            @Override
            public int compare(String str1, String str2)
            {
                // compare the length of strings
                return Integer.compare(str1.length(), str2.length());
            }
        });

        // convert the sorted List back to a LinkedHashSet
        LinkedHashSet<String> sortedFruits = new LinkedHashSet<>(list);

        System.out.println("Custom sorted order:");
        for (String fruit : sortedFruits) {
            System.out.println(fruit);
        }
    }
}

Output

Original order:
Kiwi
Strawberry
Mango
Plum
Custom sorted order:
Kiwi
Plum
Mango
Strawberry

Explanation of the above Program:

• We have created a LinkedHashSet objects and its type of String.
• After that we have added all the elements in LinkedHashSet objects of the String.
• Next, we convert the LinkedHashSet to List of the String.
• This List is sorting all elements by using custom Comparator interface.
• After that we convert List to LinkedHashSet of all String elements in sorted custom order.