Kotlin Numeric Literals

Question

I noticed that I can convert a double value into an integer like this.

var array = kotlin.arrayOfNulls<Int>(10)

for( i in array.indices ){
    array[i] = ( Math.random().toInt() )
}

If Math.random() returns a double value, how can a double value have a method named toInt()? Are numerical values also objects?

Answer 1

Yes, instances of numeric types are Kotlin objects. Quoting from the Kotlin docs:

In Kotlin, everything is an object in the sense that we can call member functions and properties on any variable. Some types are built-in, because their implementation is optimized, but to the user they look like ordinary classes.

In practice, non-nullable instances (e.g. Double as opposed to Double?) are represented under the hood with JVM primitives.

Answer 2

In Java, any object that extends Number has the ability to invoke intValue. I would presume that Kotlin is exposing that API there.