ArrayList vs. LinkedList — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Published on December 14, 2023
ArrayList is a dynamic array-based list, while LinkedList is a doubly-linked list.
Difference Between ArrayList and LinkedList
Table of Contents
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Key Differences
ArrayList is a dynamic array-based implementation of the Java List interface. It resizes itself automatically when elements are added or removed. On the other hand, LinkedList is a doubly-linked list implementation of the Java List and Deque interfaces. Unlike the ArrayList, LinkedList consists of nodes where each node contains a data element and a reference to the next and previous nodes.
ArrayList offers constant time complexity O(1) for random access due to its array nature, which means accessing any element is quick. LinkedList, in contrast, requires O(n) time for random access because one must traverse the list to access an element. However, LinkedList has an advantage when it comes to insertion and deletion at the beginning or in the middle.
ArrayList requires memory for the array and has overhead when resizing. When the ArrayList grows, it may sometimes need to be resized, causing potential performance impacts. LinkedList, conversely, uses more memory per element (due to storing two references per element, previous and next) but does not need resizing.
In ArrayList, adding or removing elements in the middle can be costly in terms of performance because elements need to be shifted. LinkedList provides faster insertions or deletions as it only needs to update the next and previous references of its nodes, making it a good choice for frequent insertions or deletions.
When considering performance and memory usage, it's essential to select the appropriate list type. If random access is more frequent, ArrayList might be preferable, but if insertions or deletions are frequent, LinkedList could be a better choice.
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Comparison Chart
Underlying Structure
Dynamic array
Doubly-linked list
Random Access
Fast (O(1) for any position)
Slow (O(n) as it needs traversal)
Memory Usage
Less memory (only data)
More memory (data + two references for each node)
Insertions/Deletions
Slower in middle (requires shift)
Faster (only requires reference change)
Resizing Overhead
Might need resizing and copying to a larger array
Doesn't need resizing
Compare with Definitions
ArrayList
Part of Java's Collections framework.
When working with Java, she often used ArrayList for its flexibility.
LinkedList
Comprises nodes with data and references to next and previous nodes.
Each node in the LinkedList contains both the data and pointers to its neighbors.
ArrayList
Has potential overhead during resizing.
When the ArrayList grew beyond its capacity, it took a moment to accommodate the new items.
LinkedList
Part of Java's Collections and Deque frameworks.
The flexibility of LinkedList, being part of both Collections and Deque, was commendable.
ArrayList
A dynamic array-based list in Java.
She stored the names in an ArrayList to ensure dynamic resizing.
LinkedList
Consumes more memory per element than ArrayList.
Although the LinkedList was versatile, its higher memory consumption per element was a downside.
ArrayList
Supports fast random access to elements.
Using an ArrayList, she quickly fetched the tenth item.
LinkedList
A doubly-linked list implementation in Java.
For his application, he chose a LinkedList because of its fast insertions.
ArrayList
Resizes itself automatically as needed.
The beauty of the ArrayList is its ability to expand without manual intervention.
LinkedList
Offers faster insertions and deletions compared to ArrayList.
When speed of insertion was crucial, he always leaned towards LinkedList.
Common Curiosities
Which uses more memory: ArrayList or LinkedList?
LinkedList uses more memory because of its two references (next and previous) for each node.
Which is faster for random access: ArrayList or LinkedList?
ArrayList is faster due to its array nature, offering O(1) access.
What is an ArrayList in Java?
An ArrayList is a dynamic array-based implementation of the List interface in Java.
How is LinkedList different from ArrayList?
LinkedList is a doubly-linked list, whereas ArrayList is array-based.
When should I use ArrayList over LinkedList?
Use ArrayList when random access or memory efficiency is a priority.
Do ArrayList and LinkedList both implement the List interface in Java?
Yes, both implement the List interface.
Why might one choose LinkedList over ArrayList?
LinkedList is preferred for frequent insertions or deletions.
Can LinkedList have duplicate elements like ArrayList?
Yes, both ArrayList and LinkedList can contain duplicate elements.
Is the resizing operation in ArrayList costly?
Yes, resizing can introduce overhead as it requires array copying.
Are operations like add or remove faster in LinkedList?
Yes, especially for insertions or deletions at the start or in the middle.
How does iteration speed compare between ArrayList and LinkedList?
Both offer linear time iteration, but ArrayList might have slight advantages due to memory locality.
Are there any thread-safety differences between ArrayList and LinkedList?
By default, both ArrayList and LinkedList are not thread-safe, but they can be wrapped in synchronized counterparts.
Can both ArrayList and LinkedList be synchronized?
Yes, both can be synchronized using utility methods.
Which one is better for stack operations: ArrayList or LinkedList?
LinkedList is generally preferred because of its efficient insertions and deletions at the ends.
How do ArrayList and LinkedList handle capacity?
ArrayList has a capacity that can grow, while LinkedList doesn't have a fixed capacity as it uses nodes.
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Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
