ArrayList vs LinkedList
- ArrayList is backed by a dynamic array
- LinkedList is backed by a doubly linked list
Core Difference
| Feature | ArrayList | LinkedList | |——–|———-|————| | Structure | Index-based data structure where each element has an index | Node-based structure; each node contains previous reference, value, and next reference | | Insertion & Removal | Slow in the middle due to shifting elements | Fast from any position; only references are updated | | Time Complexity (Insert/Delete) | O(n) | O(1) | | Element Retrieval | Fast due to direct index access | Slow; requires traversal | | Time Complexity (Access) | O(1) | O(n) | | Access Type | Supports random access | Does not support random access | —
ArrayList
An ArrayList stores elements in a contiguous array.
Characteristics
- Very fast for read/access
- Slower for insert/delete in middle
- Automatically resizes when full
When to use
- Frequent read operations
- Index-based access needed
- Less insert/delete in middle
“ArrayList is preferred when read operations are more frequent.”
LinkedList
A LinkedList stores elements as nodes, each pointing to previous and next.
Characteristics
- Slower access
- Faster insertion/deletion once position is known
- Uses more memory due to pointers
When to use
- Frequent insert/delete operations
- Queue / Deque operations
- Less random access
- ArrayList → Fast access
- LinkedList → Fast insert/delete