strawman.scala

class Account(val accountNo: String, var balance: Int){
  def credit(amount: Int) = balance = balance + amount
  def debit(amount: Int) = balance = balance - amount
}

object Bank{
        
  val accounts = Map("from" -> new Account("from", 500), "to" -> new Account("to", 500) )

  def transfer(fromNo: String, toNo: String, amount: Int): Unit = {
    val (from, to) = (accounts(fromNo), accounts(toNo))
    if(from.balance > amount){
      to.credit(amount)
      from.debit(amount)
    }
  }
  
  def main(args: Array[String]): Unit = {
    Bank.transfer("from", "to", 50)
  }
}