LinkedList in Java

In tutorial, you’ll learn about LinkedList in Java, Key Features of LinkedList, Importing LinkedList, Creating a LinkedList, Adding Elements to a LinkedList, Accessing Elements in a LinkedList​ and more along with examples.

​What is LinkedList in Java

• A LinkedList is a linear data structure where elements are stored in nodes, and each node points to the next node in the sequence.
• Unlike arrays or ArrayLists, LinkedLists don’t store elements in contiguous memory locations.
• Instead, each element is represented by a node containing both the data and a reference (or link) to the next node in the sequence.
• The last node typically points to null, indicating the end of the list.

Key Features of LinkedList​

• Doubly-Linked List: Each element (node) in a LinkedList contains a reference to both the next and previous element, allowing for efficient insertions and deletions.
• Dynamic Size: The size of a LinkedList can grow and shrink dynamically as elements are added or removed.
• Homogeneous Elements: Typically, LinkedList holds elements of a single type, specified when the LinkedList is declared.
• Indexed Access: Elements can be accessed using their index, although this is less efficient compared to ArrayList.

Importing LinkedList​

To use LinkedList, you need to import it from the java.util package.

import java.util.LinkedList;

Creating a LinkedList​

You can create a LinkedList using its constructor. You can specify the type of elements it will hold using generics.

LinkedList<String> stringList = new LinkedList<>();
LinkedList<Integer> intList = new LinkedList<>();

Adding Elements to a LinkedList​

You can add elements to a LinkedList using the add method. You can add elements at the end, at a specific position, or at the beginning.

stringList.add("Hello"); // Adds to the end
stringList.addFirst("Start"); // Adds to the beginning
stringList.addLast("End"); // Adds to the end
intList.add(10); // Adds to the end
intList.add(1, 20); // Adds 20 at index 1

Accessing Elements in a LinkedList​

You can access elements using the get method, which takes the index of the element as an argument.

String firstString = stringList.get(0);
int firstInt = intList.get(0);

System.out.println("First String: " + firstString); // Outputs: First String: Start
System.out.println("First Integer: " + firstInt); // Outputs: First Integer: 10

Modifying Elements in a LinkedList​

You can modify elements using the set method, which takes the index and the new value.

stringList.set(0, "Hi");
System.out.println("Modified First String: " + stringList.get(0));    
// Outputs: Modified First String: Hi

Removing Elements from a LinkedList​

You can remove elements using the remove method, which can take either the index of the element or the element itself.

stringList.remove(1); // Removes the element at index 1
intList.remove(Integer.valueOf(20)); // Removes the element 20

Iterating Over a LinkedList​

You can iterate over a LinkedList using a for loop, an enhanced for loop, or an iterator.

Using a For Loop​

for (int i = 0; i < stringList.size(); i++) {
    System.out.println("Element at index " + i + ": " + stringList.get(i));
}

Using an Enhanced For Loop​

for (String element : stringList) {
    System.out.println("Element: " + element);
}

Example​

Here’s a complete example demonstrating the creation, manipulation, and iteration of a LinkedList in Java:

import java.util.LinkedList;

public class LinkedListExample {
    public static void main(String[] args) {
        // Create a LinkedList to store Strings
        LinkedList<String> stringList = new LinkedList<>();

        // Add elements to the LinkedList
        stringList.add("Hello");
        stringList.addFirst("Start");
        stringList.addLast("End");

        // Access elements
        String firstString = stringList.get(0);
        System.out.println("First String: " + firstString); // Outputs: First String: Start

        // Modify an element
        stringList.set(0, "Hi");
        System.out.println("Modified First String: " + stringList.get(0)); // Outputs: Modified First String: Hi

        // Remove an element
        stringList.remove(1); // Removes the element at index 1

        // Iterate over the LinkedList
        for (String element : stringList) {
            System.out.println("Element: " + element);
        }
        // Output
        //Element: Hi
        //Element: End
    }
}