Statistics over an Array Field

An array field (as opposed to ArrayList) suits classes where the data size is known and fixed: a fixed number of test scores, sensor readings, or grades. Stat methods loop over the array and compute totals, extremes, and counts.

On the AP exam, array-field classes appear in test-score, athletic-stat, and sensor FRQs.

Scores class

public class Scores {
    private int[] scores;

    public Scores(int[] data) {
        this.scores = data;
    }

    public int total() {
        int sum = 0;
        for (int s : scores) sum += s;
        return sum;
    }

    public int max() {
        if (scores.length == 0) return 0;
        int m = scores[0];
        for (int s : scores) {
            if (s > m) m = s;
        }
        return m;
    }

    public int countAbove(int threshold) {
        int count = 0;
        for (int s : scores) {
            if (s > threshold) count++;
        }
        return count;
    }

    public double average() {
        if (scores.length == 0) return 0.0;
        return (double) total() / scores.length;
    }
}

One stat per method

Each method computes one statistic. Calls can be chained from the outside but each method stays focused.