Convert Double to ByteArray or Array Kotlin

Question

Given a Double

val double = 1.2345

How can I convert that to a Kotlin ByteArray, and/or Array<Byte>?

Whose content would look like the following after converting 1.2345

00111111 11110011 11000000 10000011
00010010 01101110 10010111 10001101

In Java, there is a sollution that involves Double.doubleToLongBits()(A static method of java.lang.Double), but in Kotlin, Double refers to Kotlin.Double, which has no such (or any other useful in this situation) method.

I don't mind if a sollution yields Kotlin.Double inaccessible in this file. :)

hotkey · Accepted Answer · 2019-04-10T15:40:33.813

22

You can still use Java Double's methods, though you will have to use full qualified names:

val double = 1.2345
val long = java.lang.Double.doubleToLongBits(double)

Then convert it to ByteArray in any way that works in Java, such as

val bytes = ByteBuffer.allocate(java.lang.Long.BYTES).putLong(long).array()

^{(note the full qualified name again)}

You can then make an extension function for this:

fun Double.bytes() = 
    ByteBuffer.allocate(java.lang.Long.BYTES)
        .putLong(java.lang.Double.doubleToLongBits(this))
        .bytes()

And the usage:

val bytes = double.bytes()

edited Apr 10 '19 at 15:40

answered Feb 14 '16 at 19:53

hotkey

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3

Also consider using `import java.lang.Double as JDouble` to turn `java.lang.Double` into `JDouble` – Jire Feb 16 '16 at 10:28
The `bytes()` method does not seem to exist. Do I have to import something? – Damn Vegetables Dec 03 '21 at 02:03
1

Perfect breaking point when you are in a Multiplatform project – Farid Dec 22 '21 at 10:37

score 4 · Answer 2 · answered May 17 '20 at 22:14

4

It looks like some convinient methods were added since your answer and you can achieve the same with

val double = 1.2345
ByteBuffer.allocate(java.lang.Double.BYTES)
     .putDouble(double).array()

answered May 17 '20 at 22:14

firen

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Convert Double to ByteArray or Array Kotlin

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