Java继承:将列表限制为子类对象

Question

我们假设我有3个类:汽车,敞篷车和车库.

汽车:

public class Car {    
    private String name;
    private String color;

    public Car(String name, String color) {
        this.name = name;
        this.color = color;
    }    
    //Getters
}

敞篷继承自汽车:

public class Convertible extends Car{
    private boolean roof;

    public Convertible(String name, String color, boolean roof) {
        super(name, color);
        this.roof = roof;
    }

    public boolean isRoof() {
        return roof;
    }
}

车库存储汽车列表:

public class Garage {
    private int capacity;
    private List<Car> cars = new LinkedList<Car>();

    //Setter for capacity
}

我怎么能创建一个只能存储Convertibles 的Garage被调用的子类ConvertibleGarage？

Answer 1

你可以使用一些泛型:

public class Garage<T extends Convertible> {
    private int capacity;
    private List<T> cars = new LinkedList<T>();

    public Garage(int capacity) {
        this.capacity = capacity;
    }
}

这意味着当您实例化a时,Garage您现在必须包含一个可转换的子参数类型或它的子类.

Garage<Convertible> cGarage = new Garage<>();

Answer 2

泛型将在这里提供帮助.

使Garage类通用Garage<T extends Car>,其中a T是可以存储的汽车类型.将cars列表重写为通用视图List<T>.

然后,a Garage<Convertible>将成为您的"ConvertibleGarage".