1. Introduction

Java developers often need to manage collections of elements with flexible insertions and deletions. In such cases, LinkedList provides a reliable alternative to ArrayList.

As Oracle describes:

“LinkedList is a linear data structure that stores elements in nodes, where each node contains a data field and a pointer to the next (and previous) node.”

This article explores the internal design, performance characteristics, and practical applications of LinkedList.

2. What is a LinkedList?

LinkedList is part of the Java Collections Framework and implements both List and Deque interfaces. It represents a doubly-linked list, where each element maintains references to both the previous and the next node.

Key properties:

• Maintains insertion order
• Allows duplicates and null values
• Efficient at insertions/deletions at the head or tail
• Not thread-safe by default

For an overview of the List interface, you may revisit our Introduction to Collections Framework.

3. Internal Structure

Internally, a LinkedList consists of nodes where each node holds:

• The data (element)
• A reference to the previous node
• A reference to the next node

There is no pre-allocated memory block, unlike arrays. This design enables constant-time insertions and deletions at both ends.

LinkedList<String> names = new LinkedList<>();
names.add("Alice");
names.addFirst("Bob");   // Insert at beginning
names.addLast("Charlie"); // Insert at end

“In a LinkedList, shifting is replaced with linking.”

4. Performance Characteristics

Understanding LinkedList complexity is essential to use it properly:

Thus, LinkedList is suitable when you have frequent add/remove operations but not when you require fast random access.

For comparison, you can read our ArrayList in Java article to see how the two structures differ.

5. Practical Use Cases

LinkedList is a strong choice when:

• Your application frequently adds/removes elements at the beginning or middle
• You need a queue or stack implementation
• Memory reallocation cost of arrays is to be avoided

Example use cases:

• Implementing undo/redo functionality
• Creating job/task queues
• Navigating browser history

6. Code Examples

Adding Elements at Both Ends

LinkedList supports efficient insertions at both head and tail:

LinkedList<String> books = new LinkedList<>();
books.addFirst("Java Basics");
books.addLast("Advanced Java");
System.out.println("Books: " + books);

Iterating Through the List

Traversing a LinkedList is similar to other lists using enhanced for-loops:

for (String book : books) {
    System.out.println(book);
}

Removing Elements

Removing elements at specific positions or ends is very efficient:

books.removeFirst();  // Removes "Java Basics"
books.removeLast();   // Removes "Advanced Java"
System.out.println("Books after removals: " + books);

7. Limitations and Alternatives

While LinkedList excels at flexibility, it has drawbacks:

• Slower access by index due to traversal
• Higher memory overhead (node references)
• Not suitable for read-intensive or random access scenarios

For such cases, ArrayList is usually a better fit.

8. Conclusion

In conclusion, LinkedList is an efficient data structure for scenarios requiring dynamic insertions and deletions. Understanding its underlying mechanics will help you decide when it’s the right tool for your project.

“Choose LinkedList when flexibility matters more than speed of access.”

You can find the complete code of this article on GitHub.