gas station

class Car {
    private String matNr;
    private int necFuel;
    public Car(final String matNr, int necFuel) {
        this.matNr = matNr;
        this.necFuel = necFuel;
    }

    public int getNecFuel() {
        return necFuel;
    }

    @Override
    public String toString() {
        return matNr + " - " + necFuel + "\n";
    }
}

class GasStation {
    private int fuel = 0;
    private Car[] cars;
    private int len = 0;

    public GasStation() {
        cars = new Car[10];
    }

    boolean feedCar(final Car car) {
        if (fuel >= car.getNecFuel()) {
            fuel -= car.getNecFuel();
            return true;
        }
        if (len != cars.length) {
            cars[len++] = car;
            return true;
        }
        return false;
    }

    @Override
    public String toString() {
        String string = "GS: " + fuel + " Q:\n";
        for (int i = 0; i < len; i++) {
            string += cars[i];
        }
        return string;
    }

    public void feedMe(int fuel) {
        this.fuel += fuel;
        int cnt = 0;
        while (cars[cnt] != null && this.fuel >= cars[cnt].getNecFuel()) {
            this.fuel -= cars[cnt].getNecFuel();
            cnt++;
        }
        for (int i = cnt; i < len; i++) {
            cars[i - cnt] = cars[i];
            cars[i] = null;
        }
        len -= cnt;
    }
}

public class Main {
    public static void main(String[] args) {
        Car car1 = new Car("12abc", 5);
        Car car2 = new Car("12vds", 10);
        Car car3 = new Car("12gef", 15);
        GasStation gs = new GasStation();
        gs.feedMe(6);
        gs.feedCar(car2);
        gs.feedCar(car1);
        gs.feedCar(car3);
        gs.feedCar(car1);
        System.out.println(gs);
        gs.feedMe(29);
        System.out.println(gs);
    }
}