.java文件中的包私有类 - 为什么它可以访问？ [英] Package-private class within a .java file - why is it accessible?

问题描述

考虑以下代码，其中 HelloWorld 类具有默认或包私有访问权限：

Consider the following code, where the HelloWorld class has default or package-private access:

class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

并假设上述代码保存在文件中名为 HelloWorld.java 。所以我的问题是：因为 HelloWorld 现在是一个包私有类，它是如何工作的？ main（）方法不应该在包中可见或可访问，我是对的吗？

And assume that the above code is saved in a file called HelloWorld.java. So my question is: since HelloWorld is now a package-private class, how does it work? The main() method should not be visible or accessible across packages, am I right?

它非常有意义如果类 HelloWorld 被声明为public，请告诉我。仅当使用默认的package-private访问声明它时才会出现混淆。

It makes perfect sense to me if the class HelloWorld is declared public. Confusion is only when it is declared with the default package-private access.

推荐答案

JVM启动在§12.1虚拟机启动JLS 。

请注意，本章说明 nothing 关于类的可见性检查。 仅指定 main 方法必须 public 。

Note that this chapter says nothing about visibility checks with regards to the class. It only specifies that the main method must be public.

这意味着根本没有检查类级别的可见性（这种情况有意义，因为还没有可用于检查可见性的上下文：其中包是来电者？）。

This means that there simply is no check for visibility on the class level (which kind-of makes sense as there is no context yet against which to check the visibility: in which "package" is the "caller"?).

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