Hash2.java

class Hash2 {
    public static void main(String[] args) {
        Car car1 = new Car(12345);
        Car car2 = new Car(12345);
        Car car3 = new Car(789);

        System.out.println(car1.hashCode());
        System.out.println(car2.hashCode());
        System.out.println(car3.hashCode());
    }
}

class Car {
    protected int speedMax = 100;
    private long id;


    public Car(long id) {
        this.id = id;
    }

    public Car() {

    }

    @Override
    public int hashCode() {
        int result = (int) (id ^ (id >>> 32));
        result = 31 * result + speedMax;
        return result;
    }

    @Override
    public boolean equals(Object o)  {
        if(this == o) return true;
        if(o == null || getClass() != o.getClass()) return false;
        Car car = (Car) o;
        if(id != car.id) return false;
        return true;
    }
    public int getSpeedMax() {
        return speedMax;
    }

    public String toString() {
        return "This is car";
    }
}

class SportCar extends Car {
    protected int speedMax = 300;

    public int getSpeedMax() {
        return speedMax;
    }
}