执行SELECT查询时PreparedStatement和ResultSet出现问题

Question

UPDATE和INSERT查询没有问题，只有SELECT有问题，这里所有代码：

try {
        String nCard = jTextField1.getText();
        String deprecate = jTextField2.getText();
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());
        String url = "jdbc:mysql://localhost:3306/visits";
        Connection conn1 = DriverManager.getConnection(url, "root", "");
        PreparedStatement pstmt = conn1.prepareStatement("INSERT INTO `visits`.`transaction` (`numbercard`, `deprecate`) VALUES (?, ?)");
        pstmt.setString(1, nCard);
        pstmt.setString(2, deprecate);
        pstmt.executeUpdate();
        DrawTable();
        PreparedStatement pstmt1 = conn1.prepareStatement("SELECT `balance` FROM `visitor` WHERE `cardID`=?");
        int nCardInt = Integer.parseInt(nCard);
        pstmt1.setInt(1, nCardInt);
        ResultSet rs1 = pstmt1.executeQuery();
        int tempBonus=rs1.getInt(1);
        tempBonus-=Integer.parseInt(deprecate);
        String bonusString = String.valueOf(tempBonus);
        PreparedStatement pstmt2 = conn1.prepareStatement("UPDATE `visitor` SET `balance`=? WHERE cardID=?");
        pstmt2.setString(1, bonusString);
        pstmt2.setString(2, nCard);
        pstmt2.executeUpdate();
    } catch (SQLException ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }

我只需要一个ID为"SELECT balance FROM visitor WHERE cardID=？"的单元格即可进行操作。如果有人能提出更简单的方法，我将不胜感激。

Answer 1

您忘记了对next()的调用，该调用将使光标前进到第一行（如果存在）。

ResultSet光标最初位于第一行之前；对该方法的第一次调用接下来使第一行成为当前行；第二个调用使第二行成为当前行，依此类推

if (rs1.next())
{
    int tempBonus=rs1.getInt(1);
}