为什么外部Java类可以访问内部类的私有成员？ [英] Why can outer Java classes access inner class private members?

问题描述

我观察到外层类可以访问内部类私有实例变量。这怎么可能？这里是一个示例代码演示相同：

  class ABC {
 class XYZ {
 private int x = 10; 
} 
 
 public static void main（String ... args）{
 ABC.XYZ xx = new ABC（）。new XYZ（）; 
 System.out.println（Hello ::+ xx.x）; ///为什么这允许？ 
} 
} 
  

为什么允许此行为？

解决方案

内部类只是一种干净地分离一些真正属于原始外部类的功能的方法。它们用于在您有两个要求时使用：

1. 您的外部类中的一些功能将是最清楚的，如果它实现

。

。

根据这些要求，内部类可以完全访问它们的外部类。因为它们基本上是外部类的成员，所以他们可以访问外部类的方法和属性（包括privates）是有意义的。

I observed that Outer classes can access inner classes private instance variables. How is this possible? Here is a sample code demonstrating the same:

class ABC{
    class XYZ{
        private int x=10;
    }

    public static void main(String... args){
        ABC.XYZ xx = new ABC().new XYZ();
        System.out.println("Hello :: "+xx.x); ///Why is this allowed??
    }
}

Why is this behavior allowed?

解决方案

The inner class is just a way to cleanly separate some functionality that really belongs to the original outer class. They are intended to be used when you have 2 requirements:

1. Some piece of functionality in your outer class would be most clear if it was implemented in a separate class.
2. Even though it's in a separate class, the functionality is very closely tied to way that the outer class works.

Given these requirements, inner classes have full access to their outer class. Since they're basically a member of the outer class, it makes sense that they have access to methods and attributes of the outer class -- including privates.

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