ArrayList VS LinkedList In Java: In this article, we will discuss the difference between ArrayList and LinkedList classes in detail. Also, we will list a few pointers with regards to below operations
- Adding or storing of an item/element {add(itemValue)}
- Removing an item/element {remove(index)}
- Retrieval of an item/element {get(index)}
Lets us move on and discuss the key differences between these 2 collection classes
ArrayList VS LinkedList
| ArrayList | LinkedList |
| To store item/elements, ArrayList uses a dynamic array or dynamically re-sizing array, i.e., an internal data structure | To store items/elements, LinkedList uses a doubly-linked list, i.e., an internal data structure |
| The initial capacity of ArrayList is 10 | It doesn’t have any initial capacity, i.e., constructs an empty list of size 0 |
| When ArrayList exceeds its capacity, then its size increases by 50% | No such thing required in LinkedList |
| When ArrayList exceeds its capacity, then an internally new array is created with 50% more of the original size andOld array data copied into the new array | No such overhead, as item/element is added to end of LinkedListDue to this, insertion is faster in LinkedList comparing with ArrayList |
| Similarly, while deleting from the middle of ArrayList involves a lot of shifting work | Deletion is much simpler in LinkedList, as previous and next links get deleted and a new link is formed |
| ArrayList internally uses an array to store the items, so retrieval becomes faster as array works on index-based | LinkedList iterate over a list to retrieve/get the required item/element |
| Overall, retrieval is faster in ArrayList when comparing with LinkedList other words, if an application requires a lot of retrieval tasks then ArrayList is the best suit | Overall, insertion and removal is faster in LinkedList when comparing with ArrayList other words, LinkedList is the best suit for an application involving a lot of insertion or deletion tasks |
| There are no memory overhead in ArrayList as it holds only actual item/elements (data) | When compared with ArrayList, LinkedList has more memory overhead as it needs to maintain addresses of the previous and next node in addition to actual item/elements (data) |
| ArrayList can be traversed in only one direction while iterating over its item/elements | LinkedList has an API to traverse in both directions while iterating over its item/elements, i.e., using descendingIterator()method |
| Elements of ArrayList stored in consecutive memory location | Elements of LinkedList stored in random memory location |
When to use ArrayList?
- When there are several retrievals like accessing employee records against the employee code
- Insertion and deletion is very less (or very minimal) for an application
- Reason: when ArrayList capacity exceeds, then internally a new array with 50% more than original size is created and older array data/items/elements are copied into the new array
- It is better to avoid ArrayList when there are the number of insertion/removal/deletion of an item/element from ArrayList as it involves a lot of shifting work internally
When to use LinkedList?
- When there are a number of insertion like for example, whenever airplane lands then its data need to be captured and stored in the list
- Also when item/element needs to be deleted from a list, then LinkedList is the best fit, when comparing with ArrayList
- Don’t use LinkedList, when there are a number of retrieval as every item need to be traversed either from beginning/end to get the required item from a list
