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Scala Identifiers

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  • Difficulty Level : Medium
  • Last Updated : 11 Nov, 2021
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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 identifiers: 

  • 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: 

Scala




// Scala program to demonstrate
// Identifiers
 
object Main
{
     
    // Main method
    def main(args: Array[String])
    {
         
    // Valid Identifiers
    var `name` = "Siya";
    var _age = 20;
    var Branch = "Computer Science";
    println("Name:" +`name`);
    println("Age:" +_age);
    println("Branch:" +Branch);
    }
}

Output:  

Name:Siya
Age:20
Branch:Computer Science

In the above example, valid identifiers are:  

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

and keywords are: 

Object, def, var, println

 

Types of Scala identifiers

Scala supports four types of identifiers: 

  • 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: 

Scala




// 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);
    }
}

Output: 

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

Example: 

Scala




// 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 identifier
    // which is used to add two values
    var sum = x + y;
    println("Display the result of + identifier:");
    println(sum);
    }
}

Output: 

Display the result of + identifier:
30
  • Mixed Identifiers: These are those identifiers which contains alphanumeric identifiers followed by undersoce and an operator identifier. 
    Example of valid mixed identifiers: 
 unary_+, sum_= 

Example: 

Scala




// 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_+);
    }
}

Output: 

Display the result of mixed identifier:
20
  • Literal Identifiers: These are those identifiers in which an arbitrary string enclosed with back ticks (`….`) . 
    Example of valid mixed identifiers: 
`Geeks`, `name` 

Example: 

Scala




// 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`);
    }
}

Output: 

Name:Siya
Age:20

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