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