java问题中的继承 [英] Inheritance in java question

问题描述

这只是java继承中的简单问题。

假设我从一个超类创建了一个基类，比如



类丰田扩展汽车{

String modelNumber ;



公共丰田（String modelNumber）

{

this.modelNumber = modelNumber;



//其余会员数据应保留为汽车类的默认值。

}



}

Car类有自己的默认值构造函数;





所以，如果我在另一个类中实例化丰田类，那么我该如何创建一个新的丰田类，使得所有成员数据保持与父类相同，并将额外数据添加为模型号;

丰田myCar =新车（）这样做吗？

有一种机制，即使我使用新的Toyota（）而不是新的Car（）创建一个新类，也会继承新的Toyota对象的默认值。

解决方案

丰田myCar =新车（）

你做不到！

因为丰田是从Car派生的，所以它可以而且应该包含Car对象没有的信息。那些信息不能发明！ ：笑：



如果你能做到这一点，那就像是说苹果是一种水果，所有的水果都是苹果，这显然是胡说八道！ />


您需要说的是

 Car myCar = new Toyota（）

因为a汽车可以是丰田，福特，或法拉利，或者......



这给你丰田的构造函数以及汽车的构造函数。

This is just simple question in java inheritance.
Suppose I created a base class from a super class like

class Toyota extends Car{
String modelNumber;

public Toyota(String modelNumber)
{
this.modelNumber = modelNumber;

//rest of the member data should remain as the default value in the car class.
}

}
the Car class has its own constructor with the default value;


so if I am instantiating a Toyota class in another class then how do i create a new toyota class such that all the member data remain same as a parent class with extra data added as a model number;
does Toyota myCar = new Car() does that ?
is there a mechanism where even if I create a new class using new Toyota() instead of new Car() will inherit the default value for the new Toyota object.

解决方案

Toyota myCar = new Car()

You can't do that!
Because Toyota is derived from Car, it can and should contain information that a Car object doesn't. That info can't be "invented"! :laugh:

If you could do that, it would be like saying "An apple is a fruit, so all fruits are apples" which is patently nonsense!

What you need to say is

Car myCar = new Toyota()

because a Car could be a Toyota, or a Ford, or a Ferrari, or ...

And that gives you the Toyota constructor as well as the Car constructor.

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