![]() If a method is annotated with this annotation type but does not override a superclass method, compilers are required to generate an error message." The purpose of annotation Override is to indicates that "a method declaration is intended to override a method declaration in a superclass. Return types are restricted to primitives, String, Class, enum, annotation, and array of the preceding types. The declarations must not have any formal parameters or a throw clause. These methods are called elements instead. ![]() A typical application programmer does not have to define annotation.Īnnotation is defined like a ordinary Java interface, but with an preceding the interface keyword (i.e., You can declare methods inside an annotation definition (just like declaring abstract method inside an interface). A tool could use the metadata information to generate additional source code, or to provide additional information for debugging, among others. One of the main reasons for adding annotation and metadata to the Java platform is to enable development and runtime tools to have a common infrastructure so as to reduce the effort required for development and deployment. Prior to the introduction of this standardized annotation feature in JDK 1.5, Java provided only ad-hoc and non-standardized mechanism, including Serializable interface (a tag interface without a method) and transient modifier (not to serialize), Javadoc comments (used by the javadoc utility to generate documentation), tag (indicates that the method should no longer be used). The runtime can discovered these metadata via the "reflection" API. ![]() They can also be stored in the class files. This additional metadata, called annotation, can be read and interrelated by the compiler or other utilities. If you look inside a JDK package (says java.lang), besides classes, interfaces, exceptions and errors, JDK 1.5 introduces two new entities: enums and annotations.Īnnotation gives you the ability to provide additional metadata alongside a Java entity (such as classes, interfaces, fields and methods). Java Programming Annotation (JDK 1.5) Introduction to Annotation ![]()
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