\begin{tikzpicture}
  \begin{abstractclass}[text width=5cm]{BankAccount}{0,0}
    \attribute{owner : String}
    \attribute{balance : Dollars = 0}

    \operation{deposit(amount : Dollars)}
    \operation[0]{withdrawl(amount : Dollars)}
  \end{abstractclass}
\end{tikzpicture}