Java教程说了以下内容：
如果注释类型t上不存在@target元通道，则可以将类型T的注释写为任何声明的修饰符，除非类型参数声明。
其他手册说，如果@target不存在@target，则不存在注释可以在任何位置使用type_use或type_parameter方案。
在这种情况下，我不确定“参数声明”的含义。该类编译，注释“ @everywhere”确实到处都是，没有任何@target注释。包括铸造操作，lambda参数和通用声明。
import java.util.ArrayList;
import java.util.function.Predicate;
@interface EveryWhere{}
public @EveryWhere class AnnotedEveryWhere<@EveryWhere T> extends @EveryWhere Object{
@EveryWhere int i = 0;
@EveryWhere <@EveryWhere T> String method(@EveryWhere ArrayList<@EveryWhere String> array) {
@EveryWhere Predicate<@EveryWhere ArrayList<@EveryWhere String>> pred =
(@EveryWhere ArrayList<@EveryWhere String> lambdaParameter)->{
@EveryWhere ArrayList<@EveryWhere String> insideLambda = new @EveryWhere ArrayList<@EveryWhere String>();
return (@EveryWhere boolean) true;};
return (@EveryWhere String) "String";
}
}
The Java Tutorials says what follows:
If an @Target meta-annotation is not present on an annotation type T , then an annotation of type T may be written as a modifier for any declaration except a type parameter declaration.
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/annotation/Target.html
Other manuals says that if @Target is not present an annotation can be used in any place except TYPE_USE or TYPE_PARAMETER scenarios.
I'm not really sure about what "parameter declaration" means in that case. This class compiles, and the annotation "@EveryWhere" is present really everywhere, without any @Target annotation. Including cast operations, lambda parameters and generics declarations.
import java.util.ArrayList;
import java.util.function.Predicate;
@interface EveryWhere{}
public @EveryWhere class AnnotedEveryWhere<@EveryWhere T> extends @EveryWhere Object{
@EveryWhere int i = 0;
@EveryWhere <@EveryWhere T> String method(@EveryWhere ArrayList<@EveryWhere String> array) {
@EveryWhere Predicate<@EveryWhere ArrayList<@EveryWhere String>> pred =
(@EveryWhere ArrayList<@EveryWhere String> lambdaParameter)->{
@EveryWhere ArrayList<@EveryWhere String> insideLambda = new @EveryWhere ArrayList<@EveryWhere String>();
return (@EveryWhere boolean) true;};
return (@EveryWhere String) "String";
}
}
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评论（1）
这取决于Java版本。 Java SE 18说
不幸的是 https://javaalmanac.io 不需要在哪个版本上找到它更改的版本所必需的详细级别。
It depends on Java version. Java SE 18 says
Unfortunately https://javaalmanac.io does not do diffs at the level of detail necessary to find out in which version it changed.