java - 如何覆盖在另一个已继承的类中赋值的变量

Question

我正在尝试获取用户输入的 super 类中汽车的座位数，但创建一个方法来打印名为“Car”的子类中的座位数。但是，当我声明存储用户输入的变量时，我收到一条错误，指出该变量不可见，这是因为它位于另一个类中。

import java.util.Scanner;

class Vehicle {

    Scanner s = new Scanner(System.in);
    private String color;
    private int noOfCylinders;
    private int noOfSeats;

    public Vehicle() {
        color = "Black";
        noOfCylinders = 0;
        noOfSeats = 1;
    }

    public Vehicle(String color, int noOfCylinders, int noOfSeats) {
        this.color = color;
        this.noOfCylinders = noOfCylinders;
        this.noOfSeats = noOfSeats;
    }

    public void getColor() {
        System.out.print("Enter color of vehicle: ");
        color = s.nextLine();
    }

    public String setColor() {
        return color;
    }

    public void getNoOfCylinders() {
        System.out.print("Enter number of cylinders: ");
        noOfCylinders = s.nextInt();
    }

    public int setNoOfCylinders() {
        return noOfCylinders;
    }

    public void getNoOfSeats() {
        System.out.print("Enter numer of seats: ");
        int noOfSeats = s.nextInt();
    }

    public String toString() {
        String information;
        information = "is " + color + " and it has " + noOfCylinders + " cylinders.";
        return information;
    }
}

public class CreateVehicle {
    public static void main(String[] args) {

        Car CarObject = new Car();
        Truck TruckObject = new Truck();

        CarObject.getColor();
        CarObject.setColor();
        CarObject.getNoOfCylinders();
        CarObject.setNoOfCylinders();
        CarObject.toString();
        CarObject.getNumOfSeats();

        TruckObject.getColor();
        TruckObject.setColor();
        TruckObject.getNoOfCylinders();
        TruckObject.setNoOfCylinders();
        TruckObject.toString();

        System.out.print(("\nThe car ")+CarObject.toString());
        System.out.print(("\nThe truck ")+TruckObject.toString());      
    }
}


class Car extends Vehicle{

    public void getNumOfSeats(){
        System.out.print("\nThe car has " + noOfSeats + " seats.");
    }
}


    class Truck extends Vehicle {
        public void printTowingCapacity() {
            System.out.print("\nThe car has " + towingCapacity + ".");
        }
    }

Answer 1

如果您想将变量保持私有(private)，可以使用父类的公共(public)函数 getNoOfSeats()。

class Car extends Vehicle{
   public void getNumOfSeats(){
      System.out.print("\nThe car has " + super.getNoOfSeats() + " seats.");
   }
}

或者只是将变量 noOfSeats 更改为 protected 或 package-protected，