Solution: Adjust Kotlin for Java usage
@file:JvmName("MoneyUtils")
package advanced.java
import java.math.BigDecimal
data class Money @JvmOverloads constructor(
val amount: BigDecimal = BigDecimal.ZERO,
val currency: Currency = Currency.EUR,
) {
companion object {
@JvmStatic
fun eur(amount: String) =
Money(BigDecimal(amount), Currency.EUR)
@JvmStatic
fun usd(amount: String) =
Money(BigDecimal(amount), Currency.USD)
@JvmField
val ZERO_EUR = eur("0.00")
}
}
@JvmName("sumMoney")
fun List<Money>.sum(): Money? {
if (isEmpty()) return null
val currency = this.map { it.currency }.toSet().single()
return Money(
amount = sumOf { it.amount },
currency = currency
)
}
operator fun Money.plus(other: Money): Money {
require(currency == other.currency)
return Money(amount + other.amount, currency)
}
enum class Currency {
EUR, USD
}
