bad_stm_example2.scala

private val map = new java.util.HashMap[String, Account]()
map.put("from", Account("from", 500))
map.put("to", Account("to", 500))

val accountsRef = Ref(map)

  def transfer(fromNo: String, toNo: String, amount: Int): Unit = {
    atomic{ implicit t => 
      var accounts = accountsRef()
      val (from, to) = (accounts.get(fromNo), accounts.get(toNo))
      if(from.balance > amount){
        accounts = accounts.put(to.accountNo, to.credit(amount))
        accounts = accounts.put(from.accountNo, from.debit(amount))
        accountsRef() = accounts
      }
    }
  }