Java ArrayList Class

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ArrayList represents a resizable array which belongs to the java.util package. ArrayList stands out from standard Java arrays by allowing dynamic resizing which makes it a more adaptable choice for handling object lists.

Key Features

  • Dynamic resizing
  • Maintains insertion order
  • Allows duplicate elements
  • Non-synchronized (not thread-safe by default)

Syntax

ArrayList list = new ArrayList();

Example

ArrayList names = new ArrayList();

Methods and Examples

Adding Elements

names.add("Alice");
names.add("Bob");
names.add("Charlie");

Accessing Elements

 System.out.println(names.get(0));

Changing Elements

names.set(1, "Brian");

Size of ArrayList

 System.out.println(names.size());

Example

import java.util.ArrayList;

public class ArrayListExample {
    public static void main(String[] args) {
        ArrayList fruits = new ArrayList<>();

        // Add elements
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Mango");

        // Print all elements
        for(String fruit : fruits) {
            System.out.println(fruit);
        }

        // Modify element
        fruits.set(1, "Grapes");

        // Remove element
        fruits.remove("Apple");

        // Check contents
        System.out.println("List contains Mango: " + fruits.contains("Mango"));
        System.out.println("Final list: " + fruits);
    }
}
Run ›
notepad

ArrayList stores objects exclusively while primitive types need to be wrapped in their corresponding wrapper classes like Integer, Double, etc.

Not thread-safe. Use Collections.synchronizedList() or CopyOnWriteArrayList for thread safety.

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