嵌套的 Java 枚举定义 - 声明为静态有区别吗？
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Nested Java enum definition - does declaring as static make a difference?
提问by serg10
I have an interface - here's a nicely contrived version as an example:
我有一个界面——这里有一个精心设计的版本作为例子：
public interface Particle {
enum Charge {
POSITIVE, NEGATIVE
}
Charge getCharge();
double getMass();
etc...
}
Is there any difference in how implementations of this would behave if I defined the Chargeenum as static - i.e. does this have any effect:
如果我将Charge枚举定义为静态，它的实现方式是否有任何不同- 即这是否有任何影响：
public interface Particle {
static enum Charge {
POSITIVE, NEGATIVE
}
Charge getCharge();
double getMass();
etc...
}
采纳答案by idrosid
No, it makes no difference. However the reason is not because it is a member declaration inside an interface, as Jon says. The real reason is according to language spec (8.9) that
不，这没有区别。然而，正如 Jon 所说，原因并不是因为它是接口内的成员声明。真正的原因是根据语言规范（8.9）
Nested enum types are implicitly static. It is permissable to explicitly declare a nested enum type to be static.
嵌套的枚举类型是隐式静态的。允许将嵌套枚举类型显式声明为静态。
At the following example static does not make any difference either (even though we have no interface):
在以下示例中，静态也没有任何区别（即使我们没有接口）：
public class A {
enum E {A,B};
}
public class A {
static enum E {A,B};
}
Another example with a nested privateenum (not implicitly public).
另一个带有嵌套私有枚举的示例（不是隐式公开的）。
public class A {
private static enum E {A,B}
}
回答by Jon Skeet
No, it makes no difference. From the language spec, section 9.5:
不，这没有区别。从语言规范，第 9.5 节：
Interfaces may contain member type declarations (§8.5). A member type declaration in an interface is implicitly
staticandpublic.
接口可能包含成员类型声明（第8.5 节）。接口中的成员类型声明是隐式
static和public。
