Complete Class with Parallel ArrayLists

When the data is tabular — each record has a name and a value — two parallel ArrayLists as fields are an AP-friendly design. The class enforces alignment by routing all changes through its methods.

On the AP exam, this design appears in roster, vote-tally, and inventory FRQs.

Gradebook class

public class Gradebook {
    private ArrayList<String> names;
    private ArrayList<Integer> scores;

    public Gradebook() {
        names = new ArrayList<>();
        scores = new ArrayList<>();
    }

    public void addStudent(String name, int score) {
        names.add(name);
        scores.add(score);
    }

    public int getScore(String name) {
        for (int i = 0; i < names.size(); i++) {
            if (names.get(i).equals(name)) {
                return scores.get(i);
            }
        }
        return -1;
    }

    public void updateScore(String name, int newScore) {
        for (int i = 0; i < names.size(); i++) {
            if (names.get(i).equals(name)) {
                scores.set(i, newScore);
                return;
            }
        }
    }

    public int size() { return names.size(); }
}

Alignment invariant

The two lists must always have the same size, and index i in each refers to the same student. Every method must preserve this.