Identifiers

In programming languages, Identifiers are used for identification purpose. In Scala, an identifier can be a

• class name
• method name
• variable name
• object name

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

In the above program we have 6 idtentifiers:

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

Note: 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 “123variable” is a not a valid Scala identifier.

object demo
{
  def main(args: Array[String])
  {
    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 identifers are:

Main, main, args, `name`, _age, Branch, +and keywords are:

Object, def, var, println

Types of Scala identifiers are

• Alphanumeric Identifiers 
• Operator Identifiers
• Mixed IdentiFiers
• Literal Identifiers

Alphanumeric Identifiers: its  start with a letter(capital or small letter) or an underscore and followed by letters, digits, or underscores. The $ character is reserved keyword and cannot be used as identifiers.

Example of valid alphanumeric identifiers:

 _stud, emp123, _1_abc_23, Student

Example of Invalid alphanumeric identifiers:

123G, $amount, -total

object demo
{
  def main(args: Array[String])
  {
    var _student5: String = "Ramesh"
    var Last_name: String = "Shukla"
    println(_student5);
    println(Last_name);
  }
}

Output:

Ramesh

Shukla

Operator Identifiers: An operator contain one or more operator character like +, :, ?, ~, or # etc.

Example of vaild operator identifiers:

 +, ++

object Main

{

    def main(args: Array[String])

    {

    var x:Int = 20;

    var y:Int = 10;

    var sum = x + y;

    println("Display the result of + identifier:");

    println(sum);

    }

}

Output:

Display the result of + identifier:

30

Mixed Identifiers: It contains alphanumeric identifiers followed by underscore and an operator identifier.

Example of vaild mixed identifiers:

 unary_+, sum_=

object Main

{

    def main(args: Array[String])

    {

    var num_+ = 20;    // num_+ is a valid mixed identifier

    println("Display the result of mixed identifier:");

    println(num_+);

    }

}

Output:

Display the result of mixed identifier:

20

Literal Identifiers: A literal is an  arbitrary string enclosed with back ticks (`….`)

Example of vaild mixed identifiers:

`Student`, `name`

object Main

{

    def main(args: Array[String])

    {

    var `name` = "Siya"

    var `age` = 20

    println("Name:" +`name`);

    println("Age:" +`age`);

    }

}

Output:

Name:Siya

Age:20