Difference between LinkedList vs ArrayList in Java

LinkedList and ArrayList both implement List Interface but how they work internally is where the differences lies. Main difference between ArrayList and LinkedList is that ArrayList is implemented using re sizable array while LinkedList is implemented using doubly LinkedList. ArrayList is more popular among Java programmer than LinkedList as there are few scenarios on which LinkedList is a suitable collection than ArrayList.

                 In this article we will see some differences between LinkedList and ArrayList and try to find out when and where to use LinkedList over ArrayList.

LinkedList vs ArrayList in Java

All the differences between LinkedList and ArrayList has there root on difference between Array and LinkedList data-structure. If you are familiar with Array and LinkedList data structure you will most likely derive following differences between them:

1) Since Array is an index based data-structure searching or getting element from Array with index is pretty fast. Array provides O(1) performance for get(index) method but remove is costly in ArrayList as you need to rearrange all elements. On the Other hand LinkedList doesn't provide Random or index based access and you need to iterate over linked list to retrieve any element which is of order O(n).

2) Insertions  are easy and fast in LinkedList as compared to ArrayList because there is no risk of resizing array

and copying content to new array if array gets full which makes adding into ArrayList of O(n) in worst case, while adding is O(1) operation in LinkedList in Java. ArrayList also needs to update its index if you insert something anywhere except at the end of array.

3) Removal is like insertions better in LinkedList than ArrayList.

4) LinkedList has more memory overhead than ArrayList because in ArrayList each index only holds actual object (data) but in case of LinkedList each node holds both data and address of next  and previous node.

When to use LinkedList and ArrayList in Java

As I said LinkedList is not as popular as ArrayList but still there are situation where a LinkedList is better choice than ArrayList in Java. Use LinkedList in Java if:

1) Your application can live without Random access. Because if you need nth element in LinkedList you need to first traverse up to nth element O(n) and than you get data from that node.

2) Your application is more insertion and deletion driver and you insert or remove more than retrieval. Since insertion or

removal doesn't involve resizing its much faster than ArrayList.

That’s all on difference between ArrayList and LinkedList in Java. Use ArrayList in Java for all there situation where you need a non-synchronized index based access. ArrayList is fast and easy to use, just try to minimize array resizing by constructing arraylist with proper initial size.

ArrayList vs. LinkedList vs. Vector 

From the hierarchy diagram, they all implement List interface. They are very similar to use. Their main difference is their implementation which causes different performance for different operations.  ArrayList is implemented as a resizable array. As more elements are added to ArrayList, its size is increased dynamically. It's elements can be accessed directly by using the get and set methods, since ArrayList is essentially an array. LinkedList is implemented as a double linked list.

                                               Its performance on add and remove is better than Arraylist, but worse on get and set methods. Vector is similar with ArrayList, but it is synchronized. ArrayList is a better choice if your program is thread-safe. Vector and ArrayList require space as more elements are added. Vector each time doubles its array size, while ArrayList grow 50% of its size each time. LinkedList, however, also implements Queue interface which adds more methods than ArrayList and Vector, such as offer(), peek(), poll(), etc.    Note: The default initial capacity of an ArrayList is pretty small. It is a good habit to construct the ArrayList with a higher initial capacity. This can avoid the resizing cost.  

ArrayList and LinkedList both implements List interface and maintains insertion order. Both are non synchronized classes.
But there are many differences between ArrayList and LinkedList classes that are given below.

ArrayList	LinkedList
1) ArrayList internally uses dynamic array to store the elements.	LinkedList internally uses doubly linked list to store the elements.
2) Manipulation with ArrayList is slow because it internally uses array. If any element is removed from the array, all the bits are shifted in memory.	Manipulation with LinkedList is faster than ArrayList because it uses doubly linked list so no bit shifting is required in memory.
3) ArrayList class can act as a list only because it implements List only.	LinkedList class can act as a list and queue both because it implements List and Deque interfaces.
4) ArrayList is better for storing and accessing data.	LinkedList is better for manipulating data.