A **LinkedHashSet** is an ordered form of [HashSet](https://www.educative.io/answers/hashset-in-java) that maintains the iteration order. A normal HashSet has no iteration order whereas, in  a LinkedHashSet, elements are sorted according to their insertion order. This class extends the HashSet class.


# Syntax
```java
LinkedHashSet<data-type> LnkdHashSet = new LinkedHashSet<data-type>();
```

# Useful methods
By default, Java provides some useful helper functions with the HashSet class. Let's look at some of them in detail:

## 1. add(Object obj)
As the name suggests, this function adds elements to the LinkedHashSet (provided that they do not exist in the HashSet prior to insertion).

## 2. remove(Object obj)
Removes a particular object from the LinkedHashSet.

## 3. clear()
 Removes *all* of the elements from the LinkedHashSet.

## 4. contains(Object obj)
Checks whether or not the specific element is present in the LinkedHashSet.

## 5. size()
​Returns the number of elements currently present in the LinkedHashSet.

## 6. isEmpty()
Checks whether or not the LinkedHashSet is empty.

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# Code
Let's take a look at a simple comparison between a HashSet and a LinkedHashSet. When we insert {1, 2, 4, 3} in the HashSet, it sorts the elements and prints them in a sorted order ( i.e., {1, 2, 3, 4} ). Whereas, in the LinkedHashSet, the elements are printed in the insertion order {1, 2, 4, 3}.

import java.util.HashSet;

class Main {
  public static void main(String[] args) {
    // Creating HashSet to store String values
    HashSet<Integer> hash_set = new HashSet<Integer>();
    // Adding elements into HashSet usind add()
    hash_set.add(1);
    hash_set.add(2);
    hash_set.add(4);
    hash_set.add(3);
    // Displaying the HashSet Unordered
    System.out.println("HashSet: " + hash_set);
    // Extracting size of HashSet
    int size = hash_set.size();
    System.out.printf("Size of HashSet is: %d \n", size);
    // Remove an element
    hash_set.remove(4);
    // Display HashSet after removal
    System.out.println("HashSet after removal: " + hash_set);

    }
}

HashSet

import java.util.LinkedHashSet;

class Main {
  public static void main(String[] args) {
    // Creating HashSet to store String values
    LinkedHashSet<Integer> hash_set = new LinkedHashSet<Integer>();
    // Adding elements into HashSet usind add()
    hash_set.add(1);
    hash_set.add(2);
    hash_set.add(4);
    hash_set.add(3);
    // Displaying the HashSet Unordered
    System.out.println("LinkedHashSet: " + hash_set);
    // Extracting size of HashSet
    int size = hash_set.size();
    System.out.printf("Size of HashSet is: %d \n", size);
    // Remove an element
    hash_set.remove(4);
    // Display HashSet after removal
    System.out.println("LinkedHashSet after removal of 4: " + hash_set);

    }
}

LinkedHashSet

What is the LinkedHashSet in Java?

Syntax LinkedHashSet LnkdHashSet = new LinkedHashSet();  