如果一个类实现一个接口，并被分配给具有该接口类型的变量，那么该对象是什么类型? [英] If an class implements an interface, and is assigned to a variable with a type of that interface, what type is that object?

问题描述

public class Motor implements Measurable {
  ...
}

public Measurable motorTemperature = new Motor();

对象motorTemperature的类型是什么?是电动机，可测量的还是两者兼而有之?

What is the type of the object motorTemperature? Is it Motor, Measurable, or both?

推荐答案

即使将对象分配给静态类型为接口Measurable的变量，该对象的运行时类型仍为Motor.类型定义行为，而接口定义无需强制转换即可调用的方法.

The runtime type of the object remains Motor even when you assign it to the variable statically typed as the interface Measurable. The type defines the behavior, while the interface defines which methods you can call without a cast.

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