Format Rupiah dengan kotlin

Converter.kt

class Converter {
    companion object {
        fun rupiah(number: Double): String{
            val localeID =  Locale("in", "ID")
            val numberFormat = NumberFormat.getCurrencyInstance(localeID)
            return numberFormat.format(number).toString()
        }
    }
}

di saya engga work gan. Malah force close appnya

fun String.toCurrencyFormat(): String {
val localeID = Locale("in", "ID")
val doubleValue = this.toDoubleOrNull() ?: return this
val numberFormat = NumberFormat.getCurrencyInstance(localeID)
numberFormat.minimumFractionDigits = 0
return numberFormat.format(doubleValue)
}

ini disaya work gan