Why use Java annotations?

Annotations provide information about java elements. Annotations can be interpreted by compiler or IDE at compile time or by JVM at runtime. Annotations can be used

• to show attributes of an element: e.g. @Deprecated, @Override, or @NotNull

• to describe the purpose of an element of the framework, e.g. @Entity, @TestCase, @WebService

• to describe the behavior of an element: @Statefull, @Transaction

Before Java 5, XML was primarily used to store information about java objects, with annotations, this information can be stored within the java code itself.