Question

public void Deposite() throws Exception
{
    try
    {
        Class.forName("com.mysql.jdbc.Driver");

        String url = "jdbc:mysql://localhost:3306/bank";

        Connection con = DriverManager.getConnection(url,"root","admin");

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter your A/c no. : " );
        acNo = Integer.parseInt(br.readLine());

        String sql = "SELECT Name,Ac_No,Balance FROM CUSTOMER WHERE Ac_No=?";
        PreparedStatement ps = con.prepareStatement(sql);
        ps.setInt(1,acNo);

        ResultSet rs = ps.executeQuery();

        while(rs.next())
        {
            String name = rs.getString("Name");
            int acNo = rs.getInt("Ac_No");
            float bal = rs.getFloat("Balance");

            System.out.println("    "+name+"        "+acNo+"        "+bal);
        }
        System.out.println("Current Bal : "+bal);

        BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter Deposite Amt : ");
        amt = Float.parseFloat(br1.readLine());

        bal = bal + amt;
        //System.out.println("Current Bal : "+bal);

        String sql1 = "UPDATE CUSTOMER SET Balance = ? WHERE Ac_No =?";
        ps = con.prepareStatement(sql1);
        ps.setInt(1,acNo);
        ps.setFloat(2,bal);
        int i = ps.executeUpdate();
        System.out.println("New Balance updated.... "+i);
        System.out.println("Transaction Successful....");

        ps.close();
        con.close();
    }
    catch(Exception e)
    {
        System.out.println(e);
    }

}

先生..我在循环播放后没有得到平衡...当我尝试更新它时......它在控制台中显示零值以进行平衡...而它仍然包含该值的值我在创建一个/ c时首先插入... 请告诉我...... console output

mysql workbench o/p

Answer 1

示例代码。 Try-with-resources负责关闭，即使抛出异常也是如此。

static class Customer {
    int acNo;
    String name;
    BigDecimal bal;
}

public static void main(String[] args) 
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter your A/c no. : " );
    int acNo = Integer.parseInt(br.readLine());

    String url = "jdbc:mysql://localhost:3306/bank";
    try (Connection con = DriverManager.getConnection(url, "root", "admin")) {
        Customer customer = loadCustomer(acNo);
        if (customer == null) {
            System.out.println("Wrong account");
        } else {
            System.out.printf("Current balance for %s, account %d: %12.2f%n",
                 customer.name, customer.acNo, customer.bal);
        }
    } catch (SQLException e) {
        e.printStacktrace();
    }
}

private static Customer loadCustomer(int accNo) throws SQLException {

    String sql = "SELECT Name, Balance FROM CUSTOMER WHERE Ac_No = ?";
    try (PreparedStatement ps = con.prepareStatement(sql)) {
        ps.setInt(1, acNo);

        try (ResultSet rs = ps.executeQuery()) {
             if (rs.next()) {
                 Customer customer = new Customer();
                 customer.acNo = acNo;
                 customer.name = rs.getString(1);
                 customer.bal = rs.getBigDecimal(2);
                 return customer;
             }
        }
    }
    return null;
}

在mysql和jdbc中输出错误的输出

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