代码：

public static int getBalance()
{         
    List <Integer> sum = new ArrayList<Integer>();

    int balance=0;
    try
    {
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/money","root","cpp");
        PreparedStatement ps = con.prepareStatement("select * from account");
        ResultSet rs = ps.executeQuery();
        while(rs.next())
        {
            sum.add(Integer.parseInt(rs.getString(1)));
            for(int i:sum)
            {
                balance += i;   
            }

        }
    }
}

当显示金额时，它已添加两倍的时间，例如，如果2000只是当前金额，则当前余额为4000