我正试图在杂货店建立一个付款台,我的代码实际上执行了我打算做的事情,但有一件事.

在我要求用户输入他们想要的项目数量之后,产品信息被收集并且工作正常,但是当它要求用户输入下一个产品的产品ID时,该行重复,我得到以下内容我的捕获中的异常：“空结果集上的非法操作”.同样,所有的计算和一切都很好,除了重复那一行.关于可能出现什么问题的任何想法？

重复的输出是这样的：

Enter product (or Exit):

ERROR1: Illegal operation on empty result set.

Enter product (or Exit):

这是代码.

try {

Class.forName("com.mysql.jdbc.Driver");

String connection = "jdbc:mysql://myDB?";

connection = connection + "user=xxx&password=xxxxxx";

Connection conn = DriverManager.getConnection(connection);

// MATA IN PRODUKTNUMMER

System.out.println("\nEnter product (or Exit):");

GroceryStore.input = GroceryStore.scan.nextLine();

PreparedStatement stmt = conn.prepareStatement(

"SELECT * "+

"FROM Products "+

"WHERE productNo = ?");

stmt.setString(1, GroceryStore.input);

ResultSet rs = stmt.executeQuery();

rs.next();

pName = rs.getString("productName");

System.out.println("Product: " + pName);

// MATA IN ANTAL

System.out.println("\nEnter amount:");

GroceryStore.amount = GroceryStore.scan.nextInt();

pPrice = rs.getDouble("productPrice");

priceRounded = new BigDecimal(pPrice).setScale(2, BigDecimal.ROUND_FLOOR);

amountRounded = new BigDecimal(GroceryStore.amount).setScale(0);

priceRounded = priceRounded.multiply(amountRounded);

GroceryStore.sum = GroceryStore.sum.add(priceRounded);

inOut.output();

inOut.input();

conn.close();

}

catch (Exception e) {

System.out.println("ERROR1: " + e.getMessage());

}