Java 中 modifer 'public' is reduntant for interface methods

標籤：

http://androidren.com/index.php?qa=322&qa_1=java-%E4%B8%AD-modifer-public-is-reduntant-for-interface-methods

經常會看到介面上寫了public修飾方法，然後IDE，比如：Eclipse或者IDEA經常會提示public是多餘的。後來就查了一下。java預設介面的方法是public和abstract的，所以真沒必要。同時，如果你使用private或者protected都會報錯。

所以，安心刪除public吧。

http://stackoverflow.com/questions/17011374/are-public-and-public-final-redundant-for-interface-methods

You cannot have a final method declared in an interface. Fields are always final but methods are always abstract (and never final). You cannot define an interface method that is to be implemented only by classes in the same package.^{* From section 9.3 of the Java Language Specification:}

Every field declaration in the body of an interface is implicitly public, static, and final. It is permitted to redundantly specify any or all of these modifiers for such fields.

and from section 9.4:

Every method declaration in the body of an interface is implicitly public (§6.6).

Every method declaration in the body of an interface is implicitly abstract, so its body is always represented by a semicolon, not a block.

It is permitted, but discouraged as a matter of style, to redundantly specify the public and/or abstract modifier for a method declared in an interface.

^{* As Paul Bellora points out in a comment, you can make the interface itself package-private (or protected, or even private) if you want to restrict its visibility.}

In addition, an interface can contain constant declarations. All constant values defined in an interface are implicitly public, static, and final. Once again, you can omit these modifiers.

另外，所有常量值預設都是public static final，不用添加。

Java 中 modifer 'public' is reduntant for interface methods