public class Airplane {

    // bereik
    private final double range;
    // capaciteit
    private final int capacity;

    public Airplane(double range, int capacity) {
        // Sanity checks.
        if(range    < 0) throw new IllegalArgumentException("Vliegtuigen kunnen niet achteruit vliegen.");
        if(capacity < 0) throw new IllegalArgumentException("Capaciteiten moeten positief zijn.");
        // OK

        this.range = range;
        this.capacity = capacity;
    }

    public double getRange() { return range; }
    public int getCapacity() { return capacity; }

    public String toString() {
        return String.format("Airplane(r = %.2f, c = %d)", range, capacity);
    }

}