Java annotation

In the Java computer programming language, an annotation is a form of syntactic metadata that can be added to Java source code. Classes, methods, variables, parameters and Java packages may be annotated. Like Javadoc tags, Java annotations can be read from source files. Unlike Javadoc tags, Java annotations can also be embedded in and read from Java class files generated by the Java compiler. This allows annotations to be retained by the Java virtual machine at run-time and read via reflection. It is possible to create meta-annotations out of the existing ones in Java. In the Java computer programming language, an annotation is a form of syntactic metadata that can be added to Java source code. Classes, methods, variables, parameters and Java packages may be annotated. Like Javadoc tags, Java annotations can be read from source files. Unlike Javadoc tags, Java annotations can also be embedded in and read from Java class files generated by the Java compiler. This allows annotations to be retained by the Java virtual machine at run-time and read via reflection. It is possible to create meta-annotations out of the existing ones in Java. The Java platform has various ad-hoc annotation mechanisms—for example, the transient modifier, or the @deprecated javadoc tag. The Java Specification Request JSR-175 introduced the general-purpose annotation (also known as metadata) facility to the Java Community Process in 2002; it gained approval in September 2004.Annotations became available in the language itself beginning with version 1.5 of the Java Development Kit (JDK). The apt tool provided a provisional interface for compile-time annotation processing in JDK version 1.5; JSR-269 formalized this, and it became integrated into the javac compiler in version 1.6. Java defines a set of annotations that are built into the language. Of the seven standard annotations, three are part of java.lang, and the remaining four are imported from java.lang.annotation. Annotations applied to Java code: Annotations applied to other annotations (also known as 'Meta Annotations'):