为什么不能调用带有实现接口的枚举列表的方法? [英] Why can't I call a method with a list of enum which implement an interface?

问题描述

我正在尝试调用一个方法，该方法采用一个接口列表和一个枚举列表(实现接口).这将产生以下编译错误:

I am trying to call a method which takes a list of Interface with a list of Enum (which implements Interface). This gives the following compile error:

The method method(List<Interface>) in the type Class is not applicable for the arguments (List<Enum>)

这是界面:

public interface Interface {
}

这是实现接口的枚举:

public enum Enum implements Interface {
}

这是调用类:

import java.util.ArrayList;
import java.util.List;

public class Class {
    public static void method(List<Interface> list){
    }

    public static void main(String[] args) {
        List <Enum> enumList = new ArrayList<Enum>();
        method(enumList); //This line gives the compile error.
    }
}

为什么会出现编译错误?在我看来，这应该起作用，因为Enum实现了该接口.

Why is there a compile error? To me it seems that it should work because the Enum implements that interface.

推荐答案

这是因为即使 Car 扩展了 Vehicle ， List< Car> 不扩展 List< Vehicle> .如果这样做，则可以执行以下操作:

This is because even is Car extends Vehicle, List<Car> does not extend List<Vehicle>. If it did, you could do the following:

List<Car> listOfCars = new ArrayList<Car>();
List<Vehicle> listOfVehicles = listOfCars;
listOfVehicles.add(new Bicycle());
// and now the list of cars contains a bicycle: not pretty.

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