Let's compare LinkedList and ArrayList w.r.t. below parameters:
1. Implementation
ArrayList is the resizable array implementation of list interface , while
LinkedList is the Doubly-linked list implementation of the list interface.
2. Performance
get(int index) or search operation
ArrayList get(int index) operation runs in constant time i.e O(1) while
LinkedList get(int index) operation run time is O(n) .
The reason behind ArrayList being faster than LinkedList is that ArrayList uses an index based system for its elements as it internally uses an array data structure, on the other hand,
LinkedList does not provide index-based access for its elements as it iterates either from the beginning or end (whichever is closer) to retrieve the node at the specified element index.
insert() or add(Object) operation
Insertions in LinkedList are generally fast as compare to ArrayList. In LinkedList adding or insertion is O(1) operation .
While in ArrayList, if the array is the full i.e worst case, there is an extra cost of resizing array and copying elements to the new array, which makes runtime of add operation in ArrayList O(n), otherwise it is O(1).
remove(int) operation
Remove operation in LinkedList is generally the same as ArrayList i.e. O(n).
In LinkedList, there are two overloaded remove methods. one is remove() without any parameter which removes the head of the list and runs in constant time O(1). The other overloaded remove method in LinkedList is remove(int) or remove(Object) which removes the Object or int passed as a parameter. This method traverses the LinkedList until it found the Object and unlink it from the original list. Hence this method runtime is O(n).
While in ArrayList remove(int) method involves copying elements from the old array to new updated array, hence its runtime is O(n).
3. Reverse Iterator
LinkedList can be iterated in reverse direction using descendingIterator() while
there is no descendingIterator() in ArrayList , so we need to write our own code to iterate over the ArrayList in reverse direction.
4. Initial Capacity
If the constructor is not overloaded, then ArrayList creates an empty list of initial capacity 10, while
LinkedList only constructs the empty list without any initial capacity.
5. Memory Overhead
Memory overhead in LinkedList is more as compared to ArrayList as a node in LinkedList needs to maintain the addresses of the next and previous node. While
In ArrayList each index only holds the actual object(data).