In programming languages, Identifiers are used for identification purpose. In Scala, an identifier can be a class name, method name, variable name or an object name.
For example :

class GFG{
    var a: Int = 20
}
object Main {
    def main(args: Array[String]) {
        var ob = new GFG();
    }
}

In the above program we have 6 idtentifiers:

• GFG: Class name
• a: Variable name
• Main: Object name
• main: Method name
• args: Variable name
• ob: Object name

Rules for defining Java Scala

There are certain rules for defining a valid Scala identifier. These rules must be followed, otherwise we get a compile-time error.

• Scala identifiers are case-sensitive.
• Scala does not allows you to use keyword as an identifier.
• Reserved Words can’t be used as an identifier like $ etc.
• Scala only allowed those identifiers which are created using below four types of identifiers.
• There is no limit on the length of the identifier, but it is advisable to use an optimum length of 4 – 15 letters only.
• Identifiers should not start with digits([0-9]). For example “123geeks” is a not a valid Scala identifier.

Example:

Output:

Name:Siya
Age:20
Branch:Computer Science

In the above example, valid identifers are:

Main, main, args, `name`, _age, Branch, +

and keywords are:

Object, def, var, println

Types of Scala identifers

Scala supports four types of identifiers:

1. Alphanumeric Identifiers: These identifiers are those identifiers which start with a letter(capital or small letter) or an underscore and followed by letters, digits, or underscores.

   Example of valid alphanumeric identifiers:

    _GFG, geeks123, _1_Gee_23, Geeks

   Example of Invalid alphanumeric identifiers:

   123G, $Geeks, -geeks

   Example:

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   // Scala program to demonstrate // Alphanumeric Identifiers    object Main  {            // Main method     def main(args: Array[String])      {                // main, _name1, and Tuto_rial are      // valid alphanumeric identifiers     var _name1: String = "GeeksforGeeks"     var Tuto_rial: String = "Scala"            println(_name1);     println(Tuto_rial);     } }

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   Output:

   GeeksforGeeks
   Scala
   

2. Operator Identifiers: These are those identifiers which contain one or more operator character like +, :, ?, ~, or # etc.
   Example of vaild operator identifiers:
   
   
   
   

    +, ++ 

   Example:

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   // Scala program to demonstrate // Operator Identifiers    object Main  {            // Main method     def main(args: Array[String])     {                // main, x, y, and sum are valid      // alphanumeric identifiers     var x:Int = 20;     var y:Int = 10;            // Here, + is a operator identifer      // which is used to add two values     var sum = x + y;      println("Display the result of + identifier:");     println(sum);     } }

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   Output:

   Display the result of + identifier:
   30
   

3. Mixed Identifiers: These are those identifiers which contains alphanumeric identifiers followed by undersoce and an operator identifier.
   Example of vaild mixed identifiers:

    unary_+, sum_= 

   Example:

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   // Scala program to demonstrate // Mixed Identifiers    object Main  {            // Main method     def main(args: Array[String])      {                // num_+ is a valid mixed identifier     var num_+ = 20;     println("Display the result of mixed identifier:");     println(num_+);     } }

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   Output:

   Display the result of mixed identifier:
   20
   

4. Literal Identifiers: These are those identifers in which an arbitrary string enclosed with back ticks (`….`) .
   Example of vaild mixed identifiers:

   `Geeks`, `name` 

   Example:

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   // Scala program to demonstrate // Literal Identifiers    object Main  {            // Main method     def main(args: Array[String])      {                // `name` and `age` are valid literal identifiers     var `name` = "Siya"     var `age` = 20     println("Name:" +`name`);     println("Age:" +`age`);     } }

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   Output:

   Name:Siya
   Age:20