JDBC的Resultset给我查询的第一行两次。为什么？

Question

所以，这是代码：

 ...
 try (Connection conn = DriverManager.getConnection(db_file);
             Statement stmt = conn.createStatement()) {
  ResultSet rs = null;
  rs = stmt.executeQuery("select order_id from orders where user_id=" + user_id + ";");
  if (!rs.isBeforeFirst() ) {
   System.out.println("no orders");
  } else {
     do {
      System.out.println(rs.getString("order_id"));
     } while (rs.next());
  }
 } catch (SQLException e) {
            System.out.println(e.getMessage());
 }
 ...

我试图在sqlite db上手动执行查询，这没关系，但是这段代码为我提供了除第一个结果外的所有结果两次。谁能帮助我找出问题所在？

例如，如果数据库有来自该user_id的3个订单，它将返回：

first
first
second
third

为什么会这样？

Answer 1

谢谢大家，这就是问题所在。我只是将其更改为：

 ...
 try (Connection conn = DriverManager.getConnection(db_file);
             Statement stmt = conn.createStatement()) {
  ResultSet rs = null;
  rs = stmt.executeQuery("select order_id from orders where user_id=" + user_id + ";");
  if (!rs.next()) {
   System.out.println("no orders");
  } else {
     do {
      System.out.println(rs.getString("order_id"));
     } while (rs.next());
  }
 } catch (SQLException e) {
            System.out.println(e.getMessage());
 }
 ...