Java构造函数继承 [英] Java Constructor Inheritance

问题描述

我想知道为什么在java构造函数不继承？你知道当你有这样的类：

I was wondering why in java constructors are not inherited? You know when you have a class like this:

public class Super {

  public Super(ServiceA serviceA, ServiceB serviceB, ServiceC serviceC){
    this.serviceA = serviceA;
    //etc
  } 

}

后来当你继承 Super 时，java会抱怨没有定义默认构造函数。解决方案显然是：

Later when you inherit from Super, java will complain that there is no default constructor defined. The solution is obviously something like:

public class Son extends Super{

  public Son(ServiceA serviceA, ServiceB serviceB, ServiceC serviceC){
    super(serviceA,serviceB,serviceC);
  }

}

此代码重复，和无用的（IMHO）...所以再次提出了问题：

This code is repetitive, not DRY and useless (IMHO)... so that brings the question again:

为什么java不支持构造函数继承？不允许这种继承有什么好处吗？

推荐答案

假设构造函数 ...那么因为每个类最终都是从Object派生的，所以每个类最终都会得到一个无参数的构造函数。这是一个坏主意。你会期望什么：

Suppose constructors were inherited... then because every class eventually derives from Object, every class would end up with a parameterless constructor. That's a bad idea. What exactly would you expect:

FileInputStream stream = new FileInputStream();

要做吗？

应该是一种轻松创建相当普通的传递构造函数的方法，但我不认为它应该是默认值。构造子类所需的参数通常不同于超类所需的参数。

Now potentially there should be a way of easily creating the "pass-through" constructors which are fairly common, but I don't think it should be the default. The parameters needed to construct a subclass are often different from those required by the superclass.

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