#Java annotations on parameters code#
However, you maybe familiar with Javadoc tags that embed metadata in Java source code but unlike Javadoc tags, Java annotations can be reflective and retrievable at run-time. Java annotations are conventionally placed before all other modifiers, but this is not a compulsion they may be freely intermixed with other modifiers. Such annotations are placed immediately before the enum constant they annotate. An annotations may be used as modifiers in any declaration, whether package, class (including enums), interface (including annotation types), field, method, formal parameter, constructor, or local variable.Īnnotations may also be used on enum constants. The purpose of an annotation is to associate information with the annotated program element. Purpose of Annotations - Adding Metadata to Java Program However, Java compiler can understand only a few Java annotations and further to Java compiler we do need annotation processing tools either developed by ourselves or third party annotation processors to parse Java annotations.
Java annotations can be extracted at the time of compiling the code by the compiler or at run time by annotation processors. That's why Java annotations are called metadata about the code. Annotations are processed by annotation processing tools to extract the provided information and to use that information for intended purpose. There may be white space between symbol and the annotation-tag name but standard coding practices advice to avoid any space between the two. Annotations present the information in a standard and structured way so that it could be used amenably by processing tools.Ī Java annotation is a modifier starts with symbol as Javadoc tags do, followed by annotation-tag name followed by zero or more element-value pairs enclosed in parenthesis.
Beside Java annotations Java programs have copious amounts of informal documentation that is typically contained within comments in the source code file but annotations are different from comments they annotate the program elements directly using annotation types to describe the form of the annotations. They associate information with the annotated program element. Java annotations are tags that we insert into source code for providing more information about the code.
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