Creating an ArrayList Object

Let’s practically use an ArrayList Object in our code. The ArrayList is a class in Java and to use a class’s functionality we have to instantiate it i.e. to construct its object.
To construct an object of a class we use a constructor. Before we jump to the constructor part let’s discuss a bit about the wrapper classes.

Wrapper classes

In Java, we cannot directly instantiate an ArrayList of the primitive data types like int, char, boolean. The reason for this is that primitive data types are not objects. For this purpose, Java has inbuilt wrapper classes which just wrap these primitive data types in a class. Below given is the list of inbuilt wrapper classes:

Primitive Data Type	Wrapper Class
boolean	Boolean
byte	Byte
char	Character
double	Double
float	Float
int	Integer
long	Long
short	Short

Note: String is not a primitive data type. These are objects instantiated from a String base class in Java, so they don’t need any wrapper class.

Generics in action

The above wrapper classes are passed to the ArrayList class as type parameters inside the pair of angle brackets <>. This is exactly the concept of Generics.
Syntactically we can generalize the declaration of an ArrayList as:

 ArrayList<Type> name;

Instantiation

The ArrayList objects can be instantiated using the keyword new and the ArrayList class are three types of constructors which are discussed below:

Empty ArrayList

The following is the basic and the most used way to instantiate an ArrayList of Integer data type.