# Introduction to ArrayList in Java ArrayList is an implementation of List interface that is backed by an array. It provides us dynamic arrays in Java. It is much similar to a dynamic array, but with the difference that it is resizable. It implements all optional list operations, and permits all elements, including null. It is found in the java.util package. ArrayList is created with an initial size. When this size is exceeded, the collection is automatically increased. The size of the collection doubles by default when full. It is an ordered collection and it allows us to access the elements by their index. It also provides us with useful methods to search, sort and manipulate the elements in it. The main features of ArrayList are: 1. Dynamic size: It can change the size of the arraylist whenever required. 2. Thread-safe: ArrayList is thread-safe, which means we can perform multiple operations at the same time without any data inconsistency. 3. Speed: ArrayList provides us with fast performance as it is non-synchronized. 4. Data manipulation: ArrayList provides us with methods to manipulate the data. It allows us to add, remove, search, sort and replace elements in the list. ArrayList is a very powerful and versatile data structure which is widely used in various Java applications. It is recommended to use ArrayList over the traditional array as it provides us with more features and flexibility.

ArrayList is a data structure in Java that implements the List interface. It is an ordered collection of objects that allows for index-based access. ArrayList is dynamic and can grow or shrink in size depending on the number of elements in the list. The following code creates an ArrayList object in Java and adds five elements to it: ```java // Create an ArrayList object ArrayList list = new ArrayList(); // Add 5 elements to the list list.add(10); list.add(20); list.add(30); list.add(40); list.add(50); ```