Question

我无法执行进一步的处理，因为我在运行此代码时关闭了ResultSet。我在sqlite数据库表的15行之后添加了值，我想找到15行的平均值，并且应该存储在ArrayList中。

以下是代码： -

try {
    Class.forName("org.sqlite.JDBC");
    c = DriverManager.getConnection("jdbc:sqlite:test.db");
    c.setAutoCommit(false);
    System.out.println("Opened database successfully3");
    stmt = c.createStatement();
    rs = stmt
            .executeQuery("SELECT TIME,BID,ASK FROM '" + title + "' ;");
    System.out.println("Opened database successfully 20");
    while (rs.next()) {
        i++;
        System.out.println(i);
        if (i > 15) {
            System.out.println("i am in");
            List<String> stocklist = new ArrayList<String>();
            String main = rs.getString(1);
            System.out.println(rs.getString(1));
            String s[] = main.split(" ", 2);
            String date = s[0];
            String time = s[1];
            stocklist.add(date);
            stocklist.add(time);
            stocklist.add(df.format(rs.getFloat("BID")));
            stocklist.add(df.format(rs.getFloat("ASK")));
            rs1 = stmt
                    .executeQuery("SELECT ASK FROM '" + title + "' ;");
            int j = 1;
            while (rs1.next()) {
                if (j < i) {
                    System.out.println(rs1.getFloat("ASK"));
                    avg = avg + rs1.getFloat("ASK");
                }
                j++;
            }
            rs1.close();

            System.out.println("i am out");
            avg = avg / 15;
            changepercent = ((rs.getFloat("ASK") - avg) / avg) * 100;
            stocklist.add(df.format(changepercent));
            stocklist.add("ETE");
            stocklist.add("HUN");
            stocklist.add("ALU");
            stocklist.add("ETE");
            stocklist.add("HUN");
            stocklist.add("ALU");
            stocklist.add("ETE");
            stocklist.add("HUN");
            hntm.addRow(stocklist);
        }
    }
    rs.close();
    stmt.close();
    c.close();
} catch (Exception e) {
    System.err.println(e.getClass().getName() + ": " + e.getMessage());
    System.exit(0);
}

Answer 1

您不应该重复使用Statement。创建新查询时，需要使用新的Statement对象。将rs1 = stmt.executeQuery("SELECT ASK FROM '" + title + "' ;");替换为rs1=c.createStatement().executeQuery("SELECT ASK FROM '" + title + "' ;");

Answer 2

这不是这个问题的答案，但是我对java.sql.SQLException: ResultSet closed也有疑问。

就我而言，查询的结果为空，因此ResultSet关闭。

PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, email);
ResultSet resultSet = preparedStatement.executeQuery();

// resultSet closed == didn't find anything
if(resultSet.isClosed())
    return false;

java.sql.SQLException：ResultSet已关闭

2 个答案: