为什么枚举可以有一个包私有构造函数? [英] Why can a enum have a package-private constructor?

问题描述

既然枚举构造函数只能由它的常量调用，为什么还允许它是包私有的?

Since an enum constructor can only be invoked by its constants, why is it then allowed to be package-private?

推荐答案

构造函数实际上不是包私有的......它是隐式private接口方法隐式public<的方式/code> 即使您不添加关键字.

The constructor actually isn't package-private... it's implicitly private the way interface methods are implicitly public even if you don't add the keyword.

JLS 的相关部分(§8.8.3) 声明:

The relevant section of the JLS (§8.8.3) states:

如果没有为普通类的构造函数指定访问修饰符，则构造函数具有默认访问权限.

If no access modifier is specified for the constructor of a normal class, the constructor has default access.

如果没有为枚举类型的构造函数指定访问修饰符，则构造函数为private.

If no access modifier is specified for the constructor of an enum type, the constructor is private.

如果枚举类型(第 8.9 节)的构造函数声明为 public 或 protected，则会导致编译时错误.

It is a compile-time error if the constructor of an enum type (§8.9) is declared public or protected.

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