How do I initialize a `List<String>` object in Java?

Abdul D.

—November 15, 2024

The ProblemThe Problem

I don’t know how to initialize a List<String> object in Java.

The SolutionThe Solution

Depending on your needs and the Java version you’re using, there are multiple ways to initialize a List<String> object.

We’ll demonstrate how to use the following:

• The ArrayList class
• The Arrays.asList() method
• The List.of() method

Note: The List.of() method can only be used with with Java 9+.

Using ArrayListUsing ArrayList

The most common way to initialize a List<String> is to use an ArrayList, which is part of the java.util package:

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> myList = new ArrayList<>();
        myList.add("Apple");
        myList.add("Banana");
        myList.add("Cherry");

        System.out.println("My List: " + myList);
    }
}

In this example, myList is an instance of ArrayList that holds String elements. The add() method adds items to the list.

Using Arrays.asList()Using Arrays.asList()

Alternatively, you can use Arrays.asList() to initialize a List with predefined values:

import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> myList = Arrays.asList("Apple", "Banana", "Cherry");
        System.out.println("My List: " + myList);
    }
}

The Arrays.asList() method creates a fixed-size list, meaning you cannot add or remove elements after initialization.

Using List.of()Using List.of()

If you are using Java 9 or later, you can use List.of() to create an immutable list:

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> myList = List.of("Apple", "Banana", "Cherry");
        System.out.println("My List: " + myList);
    }
}

Lists created with the List.of() method are immutable, meaning you cannot add, remove, or modify list elements after initialization.