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由于所有接口方法都是公共的，这是否意味着接口方法的所有实现都必须是公共的

[英]since all interface method are public, does that mean all implementation of interface method must be public as well

原文 2016-04-10 09:09:41 8 3 java/ interface/ public

since all interface method are public, does that mean all implementation of interface method must be public as well? 由于所有接口方法都是公共的，这是否意味着接口方法的所有实现都必须公开？ I have read that subclass can only assign access level that is higher than the original method. 我已经读过，子类只能分配高于原始方法的访问级别。 I have tried this with some code and it does seem to be true, but I was just wondering where can I find documentation regarding to this? 我用一些代码尝试了这个，它看起来确实如此，但我只是想知道在哪里可以找到有关此的文档？

3 个解决方案

You can find the official documentation of that requirement in the Java Language Specification . 您可以在Java语言规范中找到该要求的官方文档。

Quoting from 8.4.8.3. 引自8.4.8.3。 Requirements in Overriding and Hiding : 覆盖和隐藏的要求：

The access modifier (§6.6) of an overriding or hiding method must provide at least as much access as the overridden or hidden method, as follows: 覆盖或隐藏方法的访问修饰符（第6.6节）必须至少提供与重写或隐藏方法一样多的访问权限，如下所示：

If the overridden or hidden method is public, then the overriding or hiding method must be public; 如果被覆盖或隐藏的方法是公共的，则覆盖或隐藏方法必须是公共的; otherwise, a compile-time error occurs. 否则，发生编译时错误。

If the overridden or hidden method is protected, then the overriding or hiding method must be protected or public; 如果被覆盖或隐藏的方法受到保护，则覆盖或隐藏方法必须受到保护或公开; otherwise, a compile-time error occurs. 否则，发生编译时错误。

If the overridden or hidden method has package access, then the overriding or hiding method must not be private; 如果重写或隐藏方法具有包访问权限，则覆盖或隐藏方法不得为私有方法; otherwise, a compile-time error occurs. 否则，发生编译时错误。

As in the official Java Tutorial by Oracle: 与Oracle官方Java教程一样：

interfaces are a kind of contract all implementing classes have to stick to 接口是一种所有实现类必须坚持的契约

This means, the signature of a method, the return type and the access modifier are not allowed to be changed. 这意味着，不准的方法，该返回类型和访问修饰符的签名被改变。

https://docs.oracle.com/javase/tutorial/java/IandI/index.html https://docs.oracle.com/javase/tutorial/java/IandI/index.html

Also if you try to tag an interface-method with the @Override annotation, the compiler will throw an error. 此外，如果您尝试使用@Override注释标记interface-method，编译器将抛出错误。

Interface s are created to be an interface for using classes that implement them. Interface s的创建是使用实现它们的类的接口。

For example we implement a Comparable interface to be trusted that the class has compareTo method which can be used by other classes. 例如，我们实现Comparable接口被信任的是，类具有compareTo方法，其可以通过其它类使用。

So it's not possible and I don't see a point in doing that. 所以这是不可能的，我没有看到这样做的重点。

I didn't found a part of documentation which exactly refers to your question but it can be understood from this part: 我没有找到准确引用您的问题的文档的一部分，但从这部分可以理解：

If the overridden or hidden method is public, then the overriding or hiding method must be public; 如果被覆盖或隐藏的方法是公共的，则覆盖或隐藏方法必须是公共的; otherwise, a compile-time error occurs. 否则，发生编译时错误。