LinkedHashSet class is a Hashtable and Linked list implementation of the Set interface. It inherits the HashSet class and implements the Set interface. The Set interface inherits Collection and Iterable interfaces in hierarchical order.
However, LinkedHashSet maintain a doubly-linked list internally for all of its elements.

Java LinkedHashSet class contains unique elements only like HashSet.

Java LinkedHashSet class maintains insertion order.

Syntax for LinkedHashSet class as:

class LinkedHashSet <T>

Note: Here, <T> represents the generic type parameter. It represents which type of elements are being stored into the LinkedHashSet. Suppose, we want to create a LinkedHashSet to store a group of Strings, then we can create the object as:

LinkedHashSet<String> lhs=new LinkedHashSet<String>();

• LinkedHashSet();

This constructor is used to create a default HashSet.
e.g. LinkedHashSet hs = new LinkedHashSet();
• LinkedHashSet(Collection C);

This constructor initializing the HashSet with the elements of the collection C.
e.g. LinkedHashSet hs = new LinkedHashSet(Collection c);
• HashSet(int capacity);

Here, capacity is used initialize the size of the LinkedHashSet with the integer mentioned in the parameter.
e.g.LinkedHashSet hs = new LinkedHashSet(int capacity);
• LinkedHashSet(int capacity,float loadfactor);

This constructor can be used to initialize both the capacity and the loadfactor, also called the fillratio of the LinkedHashSet with the arguments mentioned in the parameter. When the number of elements exceeds the capacity of the hash set is multiplied with the load factor thus expanding the capacity of the LinkedHashSet.

Following are the methods of Java HashSet class are as follows:

// Java Program to Illustrate LinkedHashSet

// Importing required classes
import java.util.LinkedHashSet;

// Main class
// LinkedHashSetExample
public class HashSetExample {

    // Main driver method
    public static void main(String[] args)
    {

        // Creating an empty LinkedHashSet of string type
        LinkedHashSet linkedset
                = new LinkedHashSet();

        // Adding element to LinkedHashSet
        // using add() method
        linkedset.add("C Programming");
        linkedset.add("C++ Programming");
        linkedset.add("Java Programming");
        linkedset.add("HTML");
        // Note: This will not add new element
        // as HTML already exists
        linkedset.add("HTML");
        linkedset.add("CSS");

        // Getting size of LinkedHashSet
        // using size() method
        System.out.println("Size of LinkedHashSet = "+linkedset.size());

        System.out.println("Original LinkedHashSet:"+linkedset);

        // Removing existing entry from above Set
        // using remove() method
        System.out.println("Removing HTML from LinkedHashSet: "+ linkedset.remove("HTML"));

        // Removing existing entry from above Set
        // that does not exist in Set
        System.out.println(
                "Trying to Remove Java Script which is not "+"present: " + linkedset.remove("Java Script"));

        // Checking for element whether it is present inside
        // Set or not using contains() method
        System.out.println("Checking if Java is present="+ linkedset.contains("Java"));

        // Now lastly printing the updated LinkedHashMap
        System.out.println("Updated LinkedHashSet: "+ linkedset);
    }//end of main
}//end of class