Organizing Data: Arrays and ArrayLists

When you need to work with lots of data, like a list of students or scores, you use arrays and ArrayLists in Java.

Arrays

An array is a fixed-size container for items of the same type.

int[] scores = {95, 87, 74, 100};
System.out.println(scores[2]); // 74

Arrays are fast and simple, but their size can't change after creation.

ArrayLists

An ArrayList is like a growable array—useful when you don't know how much data you'll have.

import java.util.ArrayList;
ArrayList<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");
System.out.println(names.get(0)); // Alice

When to Use Which

• Use arrays for fixed-size collections.
• Use ArrayLists for flexible, changing data.

Real-World Examples

• Storing high scores in a game.
• Managing a list of friends in a social network app.

Quick Tips

• Arrays: scores.length
• ArrayLists: names.size()