{"id":17324,"date":"2018-06-03T04:00:40","date_gmt":"2018-06-03T04:00:40","guid":{"rendered":"https:\/\/data-flair.training\/blogs\/?p=17324"},"modified":"2021-12-04T10:15:35","modified_gmt":"2021-12-04T04:45:35","slug":"scala-annotations","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/scala-annotations\/","title":{"rendered":"Scala Annotations – Predefined & User-Defined Annotations"},"content":{"rendered":"

In our last tutorial, we study Scala Currying Function<\/strong><\/a>\u00a0and here, we will see Scala Annotations, we will learn about\u00a0Predefined Annotations in Scala Programming Langauge<\/strong><\/a>. Along with this, we will cover Scala User defined annotation and define how annotations affect code generation. At last, we will discuss some Standard Scala Annotations.<\/p>\n

So, let\u2019s begin with Scala Annotations.<\/p>\n

\"Scala<\/a>

Scala Annotations – Predefined & User-Defined Annotations<\/p><\/div>\n

Scala Annotations<\/h3>\n

Scala Annotations let us associate meta-information with definitions. We apply an annotation clause to the first definition or the declaration following it. We can use multiple annotations before a definition or declaration in any order.<\/p>\n

Scala annotation is of the form @c or @c(a1,\u2026,an), where c is a constructor for class C, which conforms to the scala.Annotation class.<\/p>\n

One such annotation is @deprecated. When we put this before a method, the compiler issues a warning when we use this method. Let\u2019s take an example of Scala Annotations.<\/p>\n

Let’s Study Scala Method Overloading with Example<\/a><\/strong><\/p>\n

scala> @deprecated\r\n| def sayhello()={\"hello\"}\r\n<console>:11: warning: @deprecated now takes two arguments; see the scaladoc.\r\n@deprecated\r\n^\r\nsayhello: ()String\r\nscala> print(sayhello())\r\n<console>:13: warning: method sayhello is deprecated\r\nprint(sayhello())\r\n^<\/pre>\n
Hello<\/p>\n
This lets us use the method; it returns a warning, but not an error.<\/p>\n
We can attach an annotation to a variable<\/a><\/strong>, an expression, a method, or any other element. This can be a class, an object, a trait, or anything else. When with a declaration or a definition, it appears in front; when with a type, it appears after. With an expression, it appears after and is separated by a colon. To an entity, we can apply more than one such annotation. Here\u2019s an<\/p>\n
example:<\/p>\n
For classes: <\/strong>@deprecated(“Use D”, “1.0”) class C { … }<\/p>\n
For types: <\/strong>String @local<\/p>\n
For variables: <\/strong>@transient @volatile var m: Int<\/p>\n
For expressions: <\/strong>(e: @unchecked) match { … }<\/p>\n
Let’s Know Reasons to Learn Scala Programming Language<\/a><\/strong><\/p>\n
Predefined Annotations in Scala<\/h3>\n
In this Scala Annotations tutorial, we will talk about four kinds of Scala annotations- Java<\/a><\/strong> Platform, Java Beans, Deprecation, and Scala Compiler annotations.<\/p>\n
\"Scala<\/a>
Scala Annotations – Predefined & User-Defined Annotations<\/p><\/div>\n
a. Java Platform Annotations in Scala<\/h4>\n
We have the following Scala annotations on the Java platform:<\/p>\n