ElonsToyCar as done live in Java Tutorial at Glyn.

ElonsToyCar.java

public class ElonsToyCar {
    private int distance;
    private int battery = 100;

    public static ElonsToyCar buy() {
        return new ElonsToyCar();
    }

    public String distanceDisplay() {
        return String.format("Driven %d meters", distance);
    }

    public String batteryDisplay() {
        if (this.battery == 0) {
            return "Battery empty";
        }

        return String.format("Battery at %d%%", battery);
    }

    public void drive() {
        if (this.battery != 0) {
            this.distance += 20;
            this.battery--;
        }
    }
}