java注释字符串[]oneArr（）；vs字符串[][]twoArr（）；公告

Question

我有以下类型的注释：

 public @interface A {
   String[] oneArr();
   String[][] twoArr();
 }

为什么第一种类型String[] oneArr();有效，而第二种类型String[][] twoArr();无效

Answer 1

从JLS (Java Language Specification)开始：

It is a compile-time error if the return type of a method declared in an annotation type is not one of the following: a primitive type, String, Class, any parameterized invocation of Class, an enum type (§8.9), an annotation type, or an array type (§10) whose element type is one of the preceding types.

下面是来自Eclipse java编译器的错误消息，更清楚一点：

Invalid type String[][] for the annotation attribute A.twoArr; only primitive type, String, Class, annotation, enumeration are permitted or 1-dimensional arrays thereof