Java-更改子类对象属性

Question

我有以下Java超类，每个属性都有构造函数、getter和setter：

public  class vehicle {
     int vehicleId;

public vehicle(int vehicleId) {
        super();
        this.vehicleId = vehicleId;

    }

     public int getVehicleId() {
    return vehicleId;
}

public void setVehicleId(int vehicleId) {
    this.vehicleId = vehicleId;
} 

和一个car子类,它扩展了vehicle超类,并具有几个独特的属性：

public class car extends vehicle{

private String wheels;

//constructor
    public car( int vehicleId, String wheels) {
        super(vehicleId);
        this.wheels = wheels;
    }

//getters and setters 

public int getWheels() {
    return wheels;
}

public void setWheels(int wheels) {
    this.wheels = wheels;
}

我创建一个新的vehicle对象链表，并向其中添加一个新的car对象：

LinkedList<vehicle> gbm = new LinkedList<vehicle>();
car car = new car(0, "");
car.setVehicleId(1);
car.setWheels("alloy");
gbm.add(car);

我可以用下面这样的函数更改属于vehicle超级类的任何属性：

public static void editVehicleId(int vid, int vehicleId) {

        for (vehicle obj : gbm) {
            if (obj.vehicleId == vid) {
                obj.setVehicleId(vehicleId);

            } else {
                System.out.println("No matching vehicle Id found - please check input");
            }
        }

    }

但是当我试图创建一个类似的函数来更改其中一个子类属性时，我得到了这个错误：“方法setWheels（int）对于类型Vehicle是未定义的”。

public static void editWheels(int vid, int wheels) {

        for (vehicle obj : gbm) {
            if (obj.vehicleId == vid) { 
                obj.setWheels(wheels);

            } else {
                System.out.println("No matching vehicle Id found - please check input");
            }
        }

    }

有人能告诉我如何编辑子类的特定属性吗？

Answer 1

您的for循环变量是车辆类型。由于这是car类的方法,因此将其设置为car对象：

for (vehicle obj : gbm) {
    if (obj.vehicleId == vid) {
        if (obj instanceof car) {
            ((car)obj).setWheels(wheels);
        }
    }
    ... rest of loop ...
}