State Tracking with Ratio Comparison

A ratio compares two counts. A class that tracks both can report their ratio as a percentage or as a decimal fraction.

Two pitfalls drive the design: integer division truncates without a cast, and division by zero crashes when no events have occurred yet.

On the AP exam, ratio-tracking classes appear in sports stats, quiz scoring, and survey FRQs.

WinLossTracker class

public class WinLossTracker {
    private int wins;
    private int losses;

    public WinLossTracker() {
        wins = 0;
        losses = 0;
    }

    public void recordWin() { wins++; }
    public void recordLoss() { losses++; }

    public int totalGames() { return wins + losses; }

    public double winRate() {
        int total = totalGames();
        if (total == 0) return 0.0;
        return (double) wins / total;
    }

    public double winPercentage() {
        return winRate() * 100;
    }

    public boolean isWinning() {
        return wins > losses;
    }
}

Why cast to double

Without the cast, wins / total truncates to 0 for any winRate less than 1. Casting promotes the division to double arithmetic.

Empty case

When no games have been recorded, the win rate is technically undefined. Most specs say return 0.0 (or some other sentinel).