Annotations Flashcards

What is the purpose of the @Native meta-annotation in Java?

Answer: It indicates that a constant field may be referenced from native code

@Native (java.lang.annotation.Native) marks a constant-valued field that may be referenced from native code, hinting to tools to generate header files.

Which annotation was introduced in Java 9 to indicate that a module exports a package for use only by specific other modules?

Answer: None — this is a module-info.java keyword, not an annotation

Qualified exports in module-info.java are declared with the 'exports ... to ...' syntax, not with a Java annotation.

Given a repeatable annotation @Tag and its container @Tags, which method should you use to retrieve all @Tag instances from a method at runtime?

Answer: method.getAnnotationsByType(Tag.class)

getAnnotationsByType(Tag.class) transparently unwraps the container and returns all repeated @Tag annotations as a flat array.

Which of the following correctly defines a single-element annotation where the element is named 'value'?

Answer: public @interface Timeout { long value(); }

The special element name 'value' allows callers to omit the element name: @Timeout(500) instead of @Timeout(value=500).

An annotation processor that generates new source files implements which interface from javax.annotation.processing?

Answer: Processor

javax.annotation.processing.Processor is the interface annotation processors implement; AbstractProcessor provides a convenient base class.

What does @SafeVarargs guarantee when applied to a method?

Answer: The method does not perform potentially unsafe operations on its varargs parameter

@SafeVarargs is a programmer assertion that the method body does not perform heap-polluting operations on the generic varargs parameter.

Which ElementType value must be included in @Target for an annotation to be usable as a type annotation (e.g., @NotNull List)?

Answer: ElementType.TYPE_USE

ElementType.TYPE_USE (added in Java 8) allows an annotation to appear wherever a type is used, including generic type arguments.