问题描述
我已阅读过，然后出现以下代码为何无效的问题？
I've read about class fromal parameters and the question then arises as to why the following code is ill-formed?
class A ：
package org.gradle;
public class A extends B.Inner{
public A(B s){
s.super(new B()); //error
s.super(); //OK
}
}
class B ：
package org.gradle;
public class B{
public class Inner{
}
}
所说内容的关键部分是：
The key part of what was said is:
所以，我希望除了默认构造函数，我们应该有一个具有以下签名的构造函数：
So, I expect that besides the default constructor, we should have a constructor with the following signature:
Inner(B b);
为什么不？
推荐答案
extra参数实际上被隐藏了 - 无论是声明它还是执行它。当你执行它，你提供一个不同的方式 - 在你的情况下，通过 s ：
The "extra" parameter is effectively hidden from you - both when you declare it, and when you execute it. When you execute it, you provide a value in a different way - in your case, via s:
s.super();
这是通过 s 作为隐藏的额外参数到 B.Inner 构造函数。所有这一切的语法有点怪异 - 我个人试图避免使用内部类在这种情况下...他们只是变得很奇怪很快。我通常喜欢静态嵌套类，如果我需要一个内部类，它几乎总是私有的。将在不同顶级类中声明的内部类进行子类化是一种奇怪的情况，IMO。
That's passing s as the hidden extra argument to the B.Inner constructor. The syntax for all of this is a little weird - and I would personally try to avoid using inner classes in this sort of situation... they just get weird very quickly. I usually prefer static nested classes, and if I do need an inner class, it's almost always private. Subclassing an inner class declared in a different top-level class is an odd situation, IMO.
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