What are constants in Kotlin and how to create them?

AndroidMobile DevelopmentApps/ApplicationsKotlin

In every programming language, we need some variable whose value will never change thoroughout the program. In Kotlin too, we have a keyword to create such a variable whose value will remain as constant throughout the program. In order to declare a value as constant, we can use the "const" keyword at the beginning. In this article, we will learn how we can declare a variable as constant in a different way.

Example: Top level declaration

Example

Kotlin const variable can be declared at the top of the programming language and it can be used throughout the file scope.

private const val My_TOP_LEVEL_CONST_VAL = "Type 1--> Example of Top Level Constant Value"

fun main()

{
   println(My_TOP_LEVEL_CONST_VAL);
}

Output

It will produce the following output −

Type 1--> Example of Top Level Constant Value

Example: Local constant

Like any other programming language, in Kotlin too, we can declare a local constant value and it will be blocked with in the specified scope. In the following example, we will create a local constant value.

Example

fun main()
{

   val MY_LOCAL_CONST="Type 2-->Example of local const value"
   println(MY_LOCAL_CONST);

}

Output

It will produce the following output −

Type 2-->Example of local const value

Example: Companion object const

Kotlin also provides an option to create a const function in the companion object. This is not recommended as per the recent programming architecture, because a companion object by default creates its own getter() and setter() methods which may cause performance issues.

Example

fun main()

{
   println(Student.MY_CONSTANT);
}

class Student(){
   companion object{
      const val MY_CONSTANT = "Type 3--> Using companion Object"
   }
}

Output

It will produce the following output −

Type 3--> Using companion Object

Example: Object declaration and direct call

A Constant variable can also be declared inside an object class. Later, this variable can be used by different means inside the program.

Example

fun main()

{

   println(MyConstant.Const_USING_OBJECT_CLASS);

}

object MyConstant {
   const val Const_USING_OBJECT_CLASS = "Type 4-->Example of const using object class"
}

Output

It will produce the following output −

Type 4-->Example of const using object class
raja
Updated on 27-Oct-2021 10:43:14

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