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Java LinkedHashSet - GeeksforGeeks

Last Updated : 11 Aug, 2025

LinkedHashSet in Java implements the Set interface of the Collection Framework. It combines the functionality of a HashSet with a LinkedList to maintain the insertion order of elements.

• Stores unique elements only.
• Maintains insertion order.
• Provides faster iteration compared to HashSet.
• Allows null elements.

Example:

import java.util.LinkedHashSet;

public class Geeks {
    public static void main(String[] args) {
      
        // Create a LinkedHashSet of Strings
        LinkedHashSet<String> lh = new LinkedHashSet<>();
        
        System.out.println("" + lh);
    }
}

public class LinkedHashSet<E> extends HashSet<E> implements Set<E>, Cloneable, Serializable

where, E is the type of elements maintained by this set.

LinkedHashSet maintains insertion order using a doubly-linked list. Unlike HashSet, it allows predictable iteration in the order elements were added.

1. LinkedHashSet(): This constructor is used to create an empty LinkedHashSet with the default capacity i.e. 16 and load factor 0.75.

LinkedHashSet<E> hs = new LinkedHashSet<E>();

2. LinkedHashSet(Collection C): Used in initializing the HashSet with the elements of the collection C.

LinkedHashSet<E> hs = new LinkedHashSet<E>(Collection c);

3. LinkedHashSet(int size): Used to initialize the size of the LinkedHashSet with the integer mentioned in the parameter.

LinkedHashSet<E> hs = new LinkedHashSet<E>(int size);

4. LinkedHashSet(int capacity, float fillRatio): Can be used to initialize both the capacity and the fill ratio, also called the load capacity 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 fill ratio thus expanding the capacity of the LinkedHashSet.

LinkedHashSet<E> hs = new LinkedHashSet<E>(int capacity, int fillRatio);

Let’s see how to perform a few frequently used operations on the LinkedHashSet.

In order to add an element to the LinkedHashSet, we can use the add() method. This is different from HashSet because in HashSet, the insertion order is not retained but is retained in the LinkedHashSet.

Example:

import java.io.*;
import java.util.*;

class Geeks {

    public static void main(String[] args) {

        // Creating an empty LinkedHashSet
        LinkedHashSet<String> lh = new LinkedHashSet<String>();

        // Adding elements to above Set using add() method
        lh.add("Geek");
        lh.add("For");
        lh.add("Geeks");

        System.out.println("LinkedHashSet : " + lh);
    }
}

LinkedHashSet : [Geek, For, Geeks]

The values can be removed from the LinkedHashSet using the remove() method.

Example:

import java.io.*;
import java.util.*;

class Geeks {

    public static void main(String[] args) {

        // Creating an empty LinekdhashSet of string type
        LinkedHashSet<String> lh
            = new LinkedHashSet<String>();

        // Adding elements to above Set using add() method
        lh.add("Geek");
        lh.add("For");
        lh.add("Geeks");
        lh.add("A");
        lh.add("B");
        lh.add("Z");

        System.out.println("" + lh);

        // Removing the element from above Set
        lh.remove("B");

        // Again removing the element
        System.out.println("After removing element " + lh);

        // Returning false if the element is not present
        System.out.println(lh.remove("AC"));
    }
}

[Geek, For, Geeks, A, B, Z]
After removing element [Geek, For, Geeks, A, Z]
false

Iterate through the elements of  LinkedHashSet using the iterator() method. The most famous one is to use the enhanced for loop.

Example:

import java.io.*;
import java.util.*;

class Geeks {

    public static void main(String[] args) {

        Set<String> lh = new LinkedHashSet<String>();

        lh.add("Geek");
        lh.add("For");
        lh.add("Geeks");
        lh.add("A");
        lh.add("B");
        lh.add("Z");

        Iterator itr = lh.iterator();

        while (itr.hasNext())
            System.out.print(itr.next() + ", ");

        System.out.println();

        for (String s : lh)
            System.out.print(s + ", ");
        System.out.println();
    }
}

Geek, For, Geeks, A, B, Z, 
Geek, For, Geeks, A, B, Z, 

• It maintains insertion order.
• It allows quick insertion, deletion and lookup of elements.
• It is useful for caching applications where insertion order is important.

• It takes higher memory as compared to HashSet due to the linked list for maintaining insertion order.
• This is slightly slower operations compared to HashSet because of the linked structure.

Notes:

• LinkedHashSet extends HashSet and maintains insertion order.
• It inherits most methods from HashSet, AbstractSet, AbstractCollection and Set interface.
• Methods like stream(), parallelStream() are useful for working with Java Streams.
• retainAll() and removeAll() are useful for performing set operations (intersection and difference).

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