Double Data type Usage and Type Conversion in Kotlin

Definition

• Double is a 64-bit number in Kotlin. Any decimal number without mentioning the number type is a double number.
• Double number is tagged with “d” or “D”
• The type can be either declared explicitly or the compiler itself has the ability to infer the type of the assigned value.
• In JVM, the characteristics of this “Double” variable is derived from the characteristics of primitive type double of Java which has a non-nullable default value.

Syntax and declaration

Thus a Double value can be declared by 3 ways as mentioned below.

1. Mentioning type explicitly

val variable_name : Double = value

for example,

val number : Double = 100.50

2. Number type is automatically inferred

val variable_name = value

for example,
//Number type is automatically inferred
val number = 100.50

3. Declaring and Initializing separately

var variable_name : Double 
variable_name = value

for example

//Declaring and Initializing separately
var number:Double 
number = 100.50

Double Datatype Example Program in Kotlin

// Double Datatype Kotlin example program
// Data type Kotlin Programs, Basic Kotlin Programs

fun main(args:Array<String>) {
    //Assigning value to Double variable explicitly
    val a : Double = 22.8e5
    //Assigned value is inferred automatically by compiler
    val b = 100.0
    println("Value of a : $a")
    println("Value of b : $b")
}

Sample Output

Value of a : 2280000.0
Value of b : 100.0

Double type Conversion Example Program in Kotlin

// Double Datatype Kotlin example program
// Data type Kotlin Programs, Basic Kotlin Programs

fun main(args: Array < String > ) {
    //Converted from String and Double type is inferred
    val num1 = "500".toDouble()

    //Conversion from String and Declaring an Double value immediately
    val num2: Double = "100.01".toDouble()

    val num3: Int = 1000
    //Conversion from Int
    val num4: Double = num3.toDouble()

    val num5: Float = 2000.31f
    //Conversion from Float
    val num6: Double = num5.toDouble()

    //Print values after conversion
    println("String to Double : num1 Value : $num1")
    println("String to Double : num2 Value : $num2")
    println("Int Value : num3 Value : $num3")
    println("Int to Double : num4 Value : $num4")
    println("Float Value : num5 Value : $num5")
    println("Float to Double : num6 Value : $num6")
}

Sample Output

String to Double : num1 Value : 500.0
String to Double : num2 Value : 100.01
Int Value : num3 Value : 1000
Int to Double : num4 Value : 1000.0
Float Value : num5 Value : 2000.31
Float to Double : num6 Value : 2000.31005859375

How It Works

This Kotlin program demonstrates Double Data type Usage and Type Conversion. It first prepares the data it needs, then performs the core operation step by step, and finally prints the output shown in the Sample Output above.

1. Declare the variables that hold the program’s data.
2. Print the final result to the console so you can compare it with the sample output.

Try changing the input values and re-running the program to see how the output changes — this is the fastest way to understand how the logic behaves.