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

问题描述

正如此处所述，在Java中覆盖私有方法是无效的因为父类的私有方法是自动最终的，并且对派生类隐藏".我的问题主要是学术性的.

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.

不允许父类的私有方法被覆盖"(即，在子类中独立实现，具有相同的签名)如何不违反封装?父类的私有方法不能被子类访问或继承，符合封装原则.它是隐藏的.

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.

那么，为什么要限制子类实现自己的具有相同名称/签名的方法?对此是否有良好的理论基础，或者这只是某种务实的解决方案?其他语言(C++ 或 C#)对此有不同的规定吗?

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?

推荐答案

你不能覆盖一个私有方法，但是你可以在派生类中引入一个没有问题的方法.这编译得很好:

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()
    {
    }
}

请注意，如果您尝试将 @Override 注释应用于 Child.foo()，您将收到编译时错误.只要您将编译器/IDE 设置为在缺少@Override 注释时向您发出警告或错误，一切都应该没问题.诚然，我更喜欢将 override 作为关键字的 C# 方法，但在 Java 中这样做显然为时已晚.

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.

至于C#对覆盖"私有方法的处理——私有方法一开始就不能是虚拟的，但是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.

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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