Linked-Hash-Set

LinkedHashSet in Java

Overview

The LinkedHashSet class in Java is part of the java.util package and implements the Set interface. It combines the characteristics of both HashSet and LinkedList by maintaining the insertion order of elements while ensuring no duplicates.

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Characteristics of LinkedHashSet

Feature	Details
Package	java.util
Allows Duplicates	No
Maintains Insertion Order	Yes
Thread-Safe	No
Allows Null Element	Yes

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Key Features of LinkedHashSet

• No Duplicates: Ensures that duplicate elements are not allowed.
• Maintains Insertion Order: The order of elements is preserved based on their insertion.
• Fast Access: Offers constant time performance for basic operations like add, remove, and contains (O(1) average time complexity).
• Hash-Based Storage: Internally backed by a HashMap and a doubly-linked list to maintain insertion order.

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How to Use LinkedHashSet

Importing LinkedHashSet

import java.util.LinkedHashSet;

Creating a LinkedHashSet

LinkedHashSet<Type> linkedHashSet = new LinkedHashSet<>();

• Example

  LinkedHashSet<String> stringSet = new LinkedHashSet<>();
  LinkedHashSet<Integer> integerSet = new LinkedHashSet<>();

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LinkedHashSet Specific Methods

The LinkedHashSet class provides several methods for efficient set operations. Below are some commonly used methods:

Method	Description	Return Type	Example
add(E e)	Adds the specified element to the set if it is not already present.	boolean	linkedHashSet.add("Apple");
contains(Object o)	Returns true if the set contains the specified element.	boolean	linkedHashSet.contains("Banana");
remove(Object o)	Removes the specified element from the set if it is present.	boolean	linkedHashSet.remove("Apple");
clear()	Removes all elements from the set.	void	linkedHashSet.clear();
isEmpty()	Checks if the set is empty.	boolean	linkedHashSet.isEmpty();
size()	Returns the number of elements in the set.	int	linkedHashSet.size();
toArray()	Converts the set to an array.	Object[]	Object[] array = linkedHashSet.toArray();

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Example Code

import java.util.*;
public class LinkedHashSetExample {
    public static void main(String[] args) {
        // Create a LinkedHashSet
        LinkedHashSet<String> linkedHashSet = new LinkedHashSet<>();

        // Add elements
        linkedHashSet.add("Apple");
        linkedHashSet.add("Banana");
        linkedHashSet.add("Cherry");

        // Check size
        System.out.println("Size of the LinkedHashSet: " + linkedHashSet.size());

        // Check if an element exists
        System.out.println("Contains 'Banana': " + linkedHashSet.contains("Banana"));

        // Remove an element
        linkedHashSet.remove("Banana");
        System.out.println("LinkedHashSet after removal: " + linkedHashSet);

        // Iterate over elements
        System.out.println("LinkedHashSet elements:");
        for (String fruit : linkedHashSet) {
            System.out.println(fruit);
        }

        // Convert to array
        Object[] array = linkedHashSet.toArray();
        System.out.println("Array from LinkedHashSet: " + Arrays.toString(array));

        // Clear the LinkedHashSet
        linkedHashSet.clear();
        System.out.println("Is LinkedHashSet empty? " + linkedHashSet.isEmpty());
    }
}

For more: LinkedHashSetDataStructure.java