Array List and Linked List

Let's talk about Java Array List and Linked List here.

Array List:

Features-

• ArrayList class implements List interface (and a couple more) and extends AbstractList class.
• ArrayList is a re-sizable array implementation which means it can automatically grow its size if required.
• ArrayList is internally backed by an Array.
• Duplicates are allowed.
• Not thread safe.

How it works:

• When we instantiate an ArrayList, it actually creates an Array of default capacity of 10 using no argument constructor. 
• When we add elements to the list, it stores the elements inside that array. Once this array gets full, it automatically creates a new array of larger capacity than the previous array (typically 1.5 time larger) and copies all the elements from old array to the new larger array.
• However it does not shrink its size if we keep deleting the elements from it.

Linked List:

Features-

• Doubly Linked List implementation of Linked List (Abstract Data Type) provided by Java.
• LinkedList class implements following interface:
• List
• Deque
• Clonable
• Serializable
• Iterable
• Collection
• Queue
• It extends AbstractSequentialList class.
• Duplicates are allowed.
• Uses Nodes to store elements.
• Dynamic memory allocation i.e. nodes will be created when required.
• Not thread safe.