java - 为什么 getAnnotation 不接受 Class<？扩展注解>

Question

为什么下一行在 Java 中产生编译错误？或者如何编写正确的泛型语法？

Class<? extends Annotation> annotation = annotations[i];
Class<? extends Annotation> anno = javaClass.getAnnotation(annotation);

方法的签名是:

public <A extends Annotation> A getAnnotation(Class<A> annotationClass)

Eclipse 编译错误:

Type mismatch: cannot convert from capture#5-of ? extends Annotation to Class<? extends Annotation>

javac编译错误:

incompatible types
    Class<? extends Annotation> anno = javaClass.getAnnotation(annotation);
                                                              ^
 required: Class<? extends Annotation>
 found:    CAP#1
 where CAP#1 is a fresh type-variable:
   CAP#1 extends Annotation from capture of ? extends Annotation

Answer 1

getAnnotation 返回注释本身 - 而不是注释的类。我怀疑你可以使用:

Class<? extends Annotation> annotationClass = annotations[i];
Annotation annotation = javaClass.getAnnotation(annotationClass);