Kotlin 中的“开放"和“公开"有什么区别? [英] What is the difference between 'open' and 'public' in Kotlin?

问题描述

我是 Kotlin 的新手，我对 open 和 public 关键字感到困惑.谁能告诉我这些关键字之间的区别?

I am new to Kotlin and I am confused between open and public keywords. Could anyone please tell me the difference between those keywords?

推荐答案

open 关键字的意思是为扩展打开":

The open keyword means "open for extension":

类上的open注解与Java的final相反:它允许其他人从这个类继承.默认，Kotlin中的所有类都是final，对应于Effective Java, Item 17: Design and document for继承，否则禁止.

The open annotation on a class is the opposite of Java's final: it allows others to inherit from this class. By default, all classes in Kotlin are final, which corresponds to Effective Java, Item 17: Design and document for inheritance or else prohibit it.

你还需要明确你想要覆盖的方法，也用 open 标记:

You also need to be explicit about methods you want to make overridable, also marked with open:

open class Base {
    open fun v() {}
    fun nv() {}
}

public 关键字充当可见性修饰符，可应用于类、函数等.请注意，public 是默认值，如果没有明确指定其他内容:

The public keyword acts as a visibility modifier that can be applied on classes, functions etc. Note that public is the default if nothing else is specified explicitly:

如果你没有指定任何可见性修饰符，默认使用public，这意味着你的声明在任何地方都可见

If you do not specify any visibility modifier, public is used by default, which means that your declarations will be visible everywhere

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