If you’ve started learning Java Collections, you’ve probably come across two popular classes: ArrayList and LinkedList.
At first, they can look almost identical. Both store multiple elements, both maintain insertion order, and both allow duplicate values.
So, a common question is:
If both are Lists, why do we need two different implementations?
The answer is simple: they store and manage data differently internally.
In this guide, we’ll understand the difference between ArrayList and LinkedList, their performance, use cases, and how to decide which one to use.
What Are ArrayList and LinkedList?
Both ArrayList and LinkedList implement Java’s List interface.
For example, you can create an ArrayList like this:
List<String> names = new ArrayList<>();
names.add("John");
names.add("Alice");
names.add("Bob");
You can also create a LinkedList:
List<String> names = new LinkedList<>();
names.add("John");
names.add("Alice");
names.add("Bob");
The code looks very similar.
The real difference is what happens behind the scenes.
What Is ArrayList?
ArrayList is a List implementation backed by a resizable array.
You can think of it like a row of boxes:
Index: 0 1 2 3
┌──────┬──────┬──────┬──────┐
│ Java │Python│ C++ │ Go │
└──────┴──────┴──────┴──────┘
Each element has an index.
For example:
ArrayList<String> languages = new ArrayList<>();
languages.add("Java");
languages.add("Python");
languages.add("C++");
System.out.println(languages.get(1));
Output:
Python
Because the elements are stored in an array-like structure, Java can quickly access an element using its index.
ArrayList Example
List<String> fruits = new ArrayList<>();
fruits.add("Apple");
fruits.add("Banana");
fruits.add("Mango");
System.out.println(fruits.get(2));
Output:
Mango
The get() operation is very efficient because Java can directly access the required index.
What Is LinkedList?
LinkedList works differently.
Instead of storing elements in a continuous array, it stores them as nodes connected to each other.
Think of it like a chain:
┌────────┐ ┌────────┐ ┌────────┐
│ Java │ ───> │ Python │ ───> │ C++ │
└────────┘ └────────┘ └────────┘
In Java, LinkedList is implemented as a doubly linked list.
Each node conceptually contains:
Previous ← Node → Next
│
Value
So every node knows about the node before it and the node after it.
How Does LinkedList Store Data?
Suppose we have:
Java → Python → C++
Now we want to insert JavaScript between Python and C++.
The links can be adjusted:
Java → Python → JavaScript → C++
The existing elements don’t need to be shifted like they would be in an array.
This is one of the key differences between ArrayList and LinkedList.
ArrayList vs LinkedList
Let’s compare their most important characteristics.
| Operation | ArrayList | LinkedList |
|---|---|---|
get(index) | O(1) | O(n) |
set(index, value) | O(1) | O(n) |
| Add at end | O(1) amortized | O(1) |
| Add at beginning | O(n) | O(1) |
| Remove from beginning | O(n) | O(1) |
| Remove from end | O(1) | O(1) |
| Search | O(n) | O(n) |
| Memory usage | Lower | Higher |
But there’s an important detail here.
You may have heard:
“LinkedList is faster for insertion and deletion.”
That’s only partly true.
The exact operation and where the element is located matter.
Why Is ArrayList Faster for get()?
Consider:
list.get(500);
With an ArrayList, Java can directly access index 500.
Conceptually:
Array
↓
[0] [1] [2] [3] ... [500]
↑
Get this
That’s why accessing an element by index is O(1).
With a LinkedList, Java has to traverse the list to reach the required node.
Node → Node → Node → Node → ... → Node 500
Therefore, indexed access is O(n).
Insertion and Deletion
This is where things become a little more interesting.
Suppose we have:
ArrayList:
[Java] [Python] [C++] [Go]
If we insert something at the beginning:
list.add(0, "JavaScript");
The existing elements may need to shift:
[JavaScript] [Java] [Python] [C++] [Go]
That’s why inserting at the beginning of an ArrayList is O(n).
With a LinkedList, adding at the beginning can be done by updating the links:
JavaScript → Java → Python → C++ → Go
This operation is O(1).
However, there’s an important catch.
If you first need to find a particular position in a LinkedList, reaching that position can take O(n).
So LinkedList isn’t automatically faster for every insertion.
Memory Usage
Another difference that beginners often overlook is memory usage.
An ArrayList primarily stores references in an internal array:
[Java] [Python] [C++] [Go]
A LinkedList requires individual node objects.
Conceptually, each node contains:
┌──────────────┐
│ Previous │
│ Value │
│ Next │
└──────────────┘
Because of this additional node and reference overhead, a LinkedList generally uses more memory than an ArrayList for the same number of elements.
When Should You Use ArrayList?
In most normal Java applications, ArrayList is a great default choice for a List.
Use ArrayList when:
- You frequently access elements using indexes.
- You mostly add elements at the end.
- You don’t frequently insert or remove elements from the beginning.
- You want better memory efficiency.
- You need a general-purpose list.
For example:
List<String> users = new ArrayList<>();
users.add("Manjeet");
users.add("Rahul");
users.add("Aman");
System.out.println(users.get(1));
This is a very common real-world use case.
When Should You Use LinkedList?
LinkedList can be useful when your application frequently adds or removes elements from the beginning or end of the list.
For example:
LinkedList<String> tasks = new LinkedList<>();
tasks.addLast("Task 1");
tasks.addLast("Task 2");
tasks.addLast("Task 3");
System.out.println(tasks.removeFirst());
Here, operations such as addFirst(), addLast(), removeFirst(), and removeLast() are efficient.
However, there’s another option worth knowing about.
What About ArrayDeque?
If you’re specifically building a queue or deque, ArrayDeque is often a better choice than LinkedList.
For example:
Deque<String> queue = new ArrayDeque<>();
queue.addLast("User 1");
queue.addLast("User 2");
queue.addLast("User 3");
System.out.println(queue.removeFirst());
So don’t automatically choose LinkedList whenever you need queue-like behavior.
Choose the collection based on the operations your application actually needs.
A Simple Real-World Analogy
Here’s an easy way to remember the difference.
Imagine an ArrayList as numbered seats in a cinema.
If someone says:
“Go to seat number 500.”
You can directly locate it.
That’s similar to:
list.get(500);
Now imagine a LinkedList as people standing in a line and holding hands.
If you want to reach person number 500, you generally have to move through the chain:
Person 1 → Person 2 → Person 3 → ... → Person 500
But if you already have a person in the chain and want to connect another person around them, changing the links can be efficient.
That’s the basic idea behind the two data structures.
Which One Should You Choose?
If you’re not sure which one to use, start with ArrayList.
It’s usually the better general-purpose choice.
Here’s a simple decision guide:
Need a general-purpose List?
↓
ArrayList
Need frequent indexed access?
↓
ArrayList
Need frequent additions/removals
at the beginning or end?
↓
LinkedList can be considered
Need a Queue or Deque?
↓
Consider ArrayDeque
ArrayList vs LinkedList: Quick Summary
ArrayList
Best for:
- Fast index-based access
- General-purpose lists
- Reading data frequently
- Lower memory overhead
Example:
List<Integer> numbers = new ArrayList<>();
LinkedList
Best for:
- Efficient additions/removals at the ends
- Situations where linked-node behavior is actually useful
- List + deque functionality when appropriate
Example:
List<Integer> numbers = new LinkedList<>();
Final Thoughts
ArrayList and LinkedList both implement the List interface, but they use completely different data structures internally.
ArrayList uses a resizable array, which makes it excellent for fast random access and a strong default choice for most lists.
LinkedList uses doubly linked nodes, which makes operations at the ends efficient but comes with additional memory overhead and slower indexed access.
The easiest way to remember it is:
ArrayList → Resizable array → Fast index access
LinkedList → Linked nodes → Efficient operations at the ends
And one important practical tip: don’t choose LinkedList just because you’ve heard that insertion and deletion are faster. Always think about the actual operations your application performs.
For most everyday List use cases, ArrayList is the first option you should consider.
