Java Fundamentals · Arrays & Collections · Lesson 17 of 22
ArrayList: A Resizable List
Concept
ArrayList: A Resizable List
Unlike arrays, an ArrayList can grow and shrink at runtime, with methods like .add() and .get() for working with its elements.
By the end of this lesson
- Explain the core idea behind ArrayList: A Resizable List.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
ExampleRunnable
import java.util.ArrayList;
ArrayList<String> names = new ArrayList<>();
names.add("Alex");
names.add("Sam");
System.out.println(names.get(0));Self-check before continuing
Without looking at the example, describe what changes when you modify one input in ArrayList: A Resizable List. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Create an ArrayList of 3 course names and print the second one.
Loading editor…
Console