What Data Type Is an ArrayList?


Larry Thompson

What Data Type Is an ArrayList?

When working with programming languages like Java, you often come across data structures that allow you to efficiently store and manipulate collections of data. One such data structure is the ArrayList.

But what data type does an ArrayList belong to? Let’s dive into it!

The ArrayList Class

The ArrayList class in Java is a part of the Java Collections Framework, which provides a set of interfaces and classes for handling collections of objects. It is implemented as a resizable array that can grow or shrink dynamically.

To use the ArrayList class, you need to import it from the java.util package:

import java.util.ArrayList;

Data Type of an ArrayList

An ArrayList in Java can be used to store objects of any reference type. This means that it can store instances of classes, interfaces, or even arrays. However, it cannot store primitive types directly.

To store primitive types in an ArrayList, you need to use their corresponding wrapper classes. For example:

ArrayList<Integer> numbers = new ArrayList<>();

In this example, we are using the wrapper class Integer to create an ArrayList that stores integers.

List vs. ArrayList

You might wonder why we use the term “ArrayList” instead of just “List.” The reason is that List is actually an interface in Java, whereas ArrayList is a class that implements this interface.

By using the term “ArrayList,” we are being specific about the actual implementation we are using. However, when declaring variables or method parameters, it is generally considered a good practice to use the interface type instead of the specific implementation type. This allows for more flexibility in case you decide to switch to a different implementation in the future.


An ArrayList in Java belongs to the data type of a class. It can store objects of any reference type, including instances of classes and interfaces.

To store primitive types, you need to use their corresponding wrapper classes. Remember that ArrayList is a class that implements the List interface.

Now that you understand what data type an ArrayList belongs to, you can confidently use this powerful data structure in your Java programs!

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