Esse pequeno método que fiz aqui não está retornando um valor de custo correto. Eu estou querendo saber se estou usando a instrução if incorretamente. Como sou novo em Java, esta é a primeira vez que uso uma instrução if com uma string envolvida. Eu não tenho livro ou professor, apenas aprendendo sozinho. Qualquer ajuda seria muito apreciada.

EDIT: código inteiro publicado

import java.util. *;

classe pública UseCarRental {

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Thank you for choosing ICT car Rentals\n"
            + "Pleae enter your full name:");
    String renterName = input.nextLine();
    System.out.println("Please enter your zip code:");
    int renterZipcode = input.nextInt();
    input.nextLine();
    System.out.println("Please enter the size car you would like:\n"
            + "economy\n"
            + "midsize\n"
            + "fullsize\n"
            + "luxury?");
    String carSize = input.next();
    System.out.println("How many days do you wish to rent this?");
    int rentalDays = input.nextInt();

    if (carSize.equals("luxury")) {
        System.out.println("Will you be wanting a chauffer (y or n");
        String chauffer = input.next();
        LuxuryCarRental rentIt = new LuxuryCarRental(renterName, 
        renterZipcode, carSize, rentalDays,chauffer);
        rentIt.display();
    } else {
        CarRental rentIt = new CarRental(renterName, renterZipcode, 
        carSize, rentalDays);
        rentIt.display();
    }




} //  end main method

} // fim da classe UseCarRental

classe CarRental {

private int days;
private int zip;
private double cost;
private String size;
private double total;
private String name;

    CarRental(String renterName, int renterZipcode, String carSize, int rentalDays){
        this.days = rentalDays;
        this.zip = renterZipcode;
        this.name = renterName;
        this.size = carSize;
    }

    double getCost(){
        if(size.equals("economy")){
            cost = 29.99;
        }
        if(size.equals("midsize")){
            cost = 38.99;
        }
        if(size.equals("fullsize")){
            cost = 43.50;
        }
        return cost;
    } 

    void display(){
        System.out.println("Thank you for using our service.");
        System.out.println("Your order is as follows:");
        System.out.println("Name: " + name);
        System.out.println("Zip code: " + zip);
        System.out.println("Car size: " + size);
        System.out.println("Cost per day: " + cost);
        System.out.println("Days requested: " + days);
        total = days * cost;
        System.out.println("Total cost: " + total);
        System.out.println("If any of the above information is incorrect, too bad bud, because it isn't.");
    }

}

classe LuxuryCarRental estende CarRental {

private int chauffer = 200;
private int days;
private int zip;
private double cost;
private String size;
private double total;
private String name;

LuxuryCarRental(String renterName, int renterZipcode, String carSize, int rentalDays, String chauffer){
    super(renterName, renterZipcode, carSize, rentalDays);
    this.days = rentalDays;
    this.zip = renterZipcode;
    this.name = renterName;
    this.size = carSize;
}

@Override
void display(){
        System.out.println("Thank you for using our service.");
        System.out.println("Your order is as follows:");
        System.out.println("Name: " + name);
        System.out.println("Zip code: " + zip);
        System.out.println("Car size: Luxury");
        System.out.println("Cost per day: " + cost);
        System.out.println("Days requested: " + days);
        System.out.println("Chauffer cost: " + chauffer);
        total = days * cost + chauffer;
        System.out.println("Total cost: " + total);
        System.out.println("If any of the above information is incorrect, too bad bud, because it isn't.");
    }

}