Vote Counting and Percentage

A vote counter holds candidate names and their tallies. Recording a vote adds a candidate (if new) or increments their tally (if existing). Percentage methods divide each tally by the total — with the usual cast and zero-guard discipline.

On the AP exam, vote-counting FRQs combine parallel ArrayLists, search-or-add logic, and ratio computation.

VoteCounter class

public class VoteCounter {
    private ArrayList<String> candidates;
    private ArrayList<Integer> votes;

    public VoteCounter() {
        candidates = new ArrayList<>();
        votes = new ArrayList<>();
    }

    public void recordVote(String name) {
        for (int i = 0; i < candidates.size(); i++) {
            if (candidates.get(i).equals(name)) {
                votes.set(i, votes.get(i) + 1);
                return;
            }
        }
        candidates.add(name);
        votes.add(1);
    }

    public int totalVotes() {
        int total = 0;
        for (int v : votes) total += v;
        return total;
    }

    public double percentFor(String name) {
        int total = totalVotes();
        if (total == 0) return 0.0;
        for (int i = 0; i < candidates.size(); i++) {
            if (candidates.get(i).equals(name)) {
                return 100.0 * votes.get(i) / total;
            }
        }
        return 0.0;
    }
}

Three patterns combined

1. Parallel ArrayLists for records.
2. Search-or-add for vote registration.
3. Cast + zero-guard for percentage.