覆盖Java中的私有方法 [英] Overriding private methods in Java

问题描述

简洁地描述了此处，覆盖Java中的私有方法无效因为父类的私有方法是自动最终的，并且从派生类中隐藏。我的问题主要是学术性的。

如何不违反封装，不允许父母的私有方法被覆盖（即，在子类中独立实施，具有相同的签名）？根据封装原则，子类无法访问或继承父级的私有方法。它是隐藏的。

那么，为什么要限制子类使用相同的名称/签名实现自己的方法？有没有一个很好的理论基础，或者这只是某种实用的解决方案？其他语言（C ++或C＃）对此有不同的规则吗？

解决方案

你不能覆盖一个私有方法，但您可以在派生类中引入一个没有问题。编译正常：

  class Base 
 {
 private void foo（）
 {
} 
} 
 
 class Child延伸基数
 {
 private void foo（）
 {
} 
} 
  

请注意，如果您尝试应用 @Override 注释到 Child.foo（）您将收到编译时错误。只要您的编译器/ IDE设置为在缺少 @Override 注释时为您提供警告或错误，一切都应该很好。不可否认，我更喜欢覆盖的C＃方法作为关键字，但在Java中显然为时已晚。

对于C＃处理覆盖私有方法 - 私有方法首先不能是虚方法，但你当然可以在基类中引入一个与私有方法同名的新私有方法。 / p>

As succinctly described here, overriding private methods in Java is invalid because a parent class's private methods are "automatically final, and hidden from the derived class". My question is largely academic.

How is it not a violation of encapsulation to not allow a parent's private method to be "overridden" (ie, implemented independently, with the same signature, in a child class)? A parent's private method cannot be accessed or inherited by a child class, in line with principles of encapsulation. It is hidden.

So, why should the child class be restricted from implementing its own method with the same name/signature? Is there a good theoretical foundation for this, or is this just a pragmatic solution of some sort? Do other languages (C++ or C#) have different rules on this?

解决方案

You can't override a private method, but you can introduce one in a derived class without a problem. This compiles fine:

class Base
{
   private void foo()
   {
   }
}

class Child extends Base
{
    private void foo()
    {
    }
}

Note that if you try to apply the @Override annotation to Child.foo() you'll get a compile-time error. So long as you have your compiler/IDE set to give you warnings or errors if you're missing an @Override annotation, all should be well. Admittedly I prefer the C# approach of override being a keyword, but it was obviously too late to do that in Java.

As for C#'s handling of "overriding" a private method - a private method can't be virtual in the first place, but you can certainly introduce a new private method with the same name as a private method in the base class.

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