static ArrayList<BankAccount> list = new ArrayList<BankAccount>();
    public Bank()
    {
        String[] alist = new String[list.size()];
        for(int i=0;i<list.size();i++)
        {
            String[i] alist+"" = list.get(i).accountNumber;
        }
        JComboBox accountnumberlist = new JComboBox(list.get(i).accountNumber);
    }