JoinString_with_overload.kt

@JvmOverloads
fun joinStrings(
        collection: Collection<String>,
        separator: String = ","
): String {
    val result = StringBuffer()
    val firstElement = 0
    for((index, word) in collection.withIndex()) {
        if(index != firstElement) result.append(separator)
        result.append(word)
    }
    return  result.toString()
}