Принцип разделения интерфейсов (Interface Segregation)

package ru.company.app;

import java.util.ArrayList;
import java.util.List;

interface ICar {
    int currentSpeed();
}

abstract class ACar implements ICar {
    private int speed;
    protected int eNumber;

    @Override
    public int currentSpeed() {
        return speed;
    }
}

interface IDriver {
    int pedals();
}

class DriverCar extends ACar implements IDriver {

    @Override
    public int pedals() {
        return 0;
    }
}

interface IInspector {
    int engineNumber();
}

class InspectorCar extends ACar implements IInspector {

    @Override
    public int engineNumber() {
        return eNumber;
    }

}

class PoliceCar extends InspectorCar implements IDriver {

    @Override
    public int pedals() {
        return 0;
    }

}

public class Main {
    public static void main(String[] args) {
        List <ACar> cars = new ArrayList <>();
        cars.add(new DriverCar());
        cars.add(new InspectorCar());
        cars.add(new PoliceCar());
    }
}