How to Create ArrayList in Java: Syntax and Examples

To create an ArrayList in Java, first import java.util.ArrayList. Then declare and initialize it using ArrayList<Type> list = new ArrayList<>();, where Type is the type of elements you want to store.

Syntax

Here is the basic syntax to create an ArrayList in Java:

• ArrayList<Type>: Declares an ArrayList that holds elements of the specified Type.
• list: The variable name for your ArrayList.
• new ArrayList<>(): Creates a new empty ArrayList instance.

java

import java.util.ArrayList;

ArrayList<Type> list = new ArrayList<>();

Example

This example shows how to create an ArrayList of strings, add some items, and print them.

java

import java.util.ArrayList;

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

        for (String fruit : fruits) {
            System.out.println(fruit);
        }
    }
}

Output

Apple
Banana
Cherry

Common Pitfalls

Common mistakes when creating or using ArrayLists include:

• Forgetting to import java.util.ArrayList.
• Not specifying the type inside angle brackets, which can cause warnings or errors.
• Trying to use primitive types like int directly instead of wrapper classes like Integer.
• Using raw types (e.g., ArrayList list = new ArrayList();) which is discouraged.

java

/* Wrong way: Missing import and raw type usage */
// ArrayList list = new ArrayList(); // Warning: raw type

/* Right way: */
import java.util.ArrayList;
ArrayList<Integer> numbers = new ArrayList<>();

Quick Reference

Action	Syntax Example
Create ArrayList	ArrayList list = new ArrayList<>();
Add element	list.add("Hello");
Get element	String item = list.get(0);
Remove element	list.remove(0);
Check size	int size = list.size();

Key Takeaways

Always import java.util.ArrayList before using ArrayList.

Use angle brackets <> to specify the type of elements stored.

Use wrapper classes like Integer for primitive types in ArrayList.

Avoid raw types to prevent warnings and ensure type safety.

Use methods like add(), get(), remove(), and size() to work with ArrayLists.