java - 公共(public)嵌套类的子类无法访问封闭类的私有(private)成员

Question

我读过一句话here 像下面这样

A nested class has access to all the private members of its enclosing class—both fields and methods. Therefore, a public or protected nested class inherited by a subclass has indirect access to all of the private members of the super class.

现在我有如下代码

类储物柜{

private String Secret = "这是我的 secret ";

公共(public)类 Util { }

}

class StealSecret 扩展了 Locker.Util { }

但是我收到如下所示的编译时错误

No enclosing instance of type Locker is available due to some intermediate constructor invocation

我无法理解到底是什么导致了编译时错误。我在链接中读到的内容是错误的吗？

请举例说明如何通过扩展内部类来访问封闭类的私有(private)成员

Answer 1

其他答案已经解释了异常的原因，但没有解决

Please give me an example explaining the way to access the private members of enclosing class by extending the inner class

您的文档中的引用指出

A nested class has access to all the private members of its enclosing class—both fields and methods.

嵌套类是在另一个类中声明的类。 Locker.Util 是一个嵌套类。 StealSecret 不是(即使它确实编译了，请参阅下面的技巧来做到这一点)。

如果您确实需要扩展该内部类并且可以访问Locker类的private成员，您'还需要在 Locker 中声明子类

例如，

public class Locker {
    private String secret = "This is my secret";

    public class Util {
    }

    public class StealSecret extends Locker.Util {
        public StealSecret() {
            System.out.println(secret); // access
        }
    }
}

<小时/>

StealSecret 类扩展了一个内部类，它需要对该内部类的封闭类的实例的引用。您可以使用此技巧来提供该引用

class StealSecret extends Locker.Util {
    public StealSecret(Locker enclosing) {
        enclosing.super();
    }
}