public Vector findAll() { con = JDBCconn.getConnection(); Vector rowData = new Vector(); try { String sql = "select * from employee order by id"; pstmt = con.prepareStatement(sql); rs = pstmt.executeQuery(); while(rs.next()) { Vector row =new Vector(); row.add(rs.getString(1)); row.add(rs.getString(2)); row.add(rs.getString(3)); rowData.add(row); } return rowData; } catch (Exception e) { // TODO: handle exception e.printStackTrace(); return null; }finally{ JDBCconn.closeConnection(); } } 该方法如何从rowdata中输出getString（1）

可以使用以下代码从rowData中输出第一个元素：

Vector row = (Vector) rowData.get(index); // index为所需行号
String str = (String) row.get(0);
System.out.println(str);

其中，`(String) row.get(0)`表示获取当前行的第一个元素并强制转换为字符串类型。

相关问题

public Vector findAll() { con = JDBCconn.getConnection(); Vector rowData = new Vector(); try { String sql = "select * from employee order by id"; pstmt = con.prepareStatement(sql); rs = pstmt.executeQuery(); while(rs.next()) { Vector row =new Vector(); row.add(rs.getString(1)); row.add(rs.getString(2)); row.add(rs.getString(3)); rowData.add(row); } return rowData; } catch (Exception e) { // TODO: handle exception e.printStackTrace(); return null; }finally{ JDBCconn.closeConnection(); } } 该方法如何输出getString（1）

您可以使用以下代码从 `rowData` 中输出第一列的值：

for (int i = 0; i < rowData.size(); i++) {
    Vector row = (Vector) rowData.get(i);
    String value = (String) row.get(0);
    System.out.println(value);
}

其中，`Vector row = (Vector) rowData.get(i)` 表示获取第 i 行数据，`(String) row.get(0)` 表示获取当前行的第一个元素并强制转换为字符串类型，`System.out.println(value)` 表示输出该元素的值。

public Vector findAll() { con = JDBCconn.getConnection(); Vector rowData = new Vector(); try { String sql = "select * from users order by id"; pstmt = con.prepareStatement(sql); rs = pstmt.executeQuery(); while(rs.next()) { Vector row =new Vector(); row.add(rs.getString(1)); row.add(rs.getString(2)); row.add(rs.getString(3)); rowData.add(row); } return rowData; } catch (Exception e) { // TODO: handle exception e.printStackTrace(); return null; }finally{ JDBCconn.closeConnection(); } } 根据此代码如何修改为只找name

可以将 SQL 语句修改为 `select name from users order by id`，即只查询 `name` 字段。同时，Vector 的元素个数也应该修改为 1，修改后的代码如下：

public Vector findAllNames() {
    con = JDBCconn.getConnection();
    Vector rowData = new Vector();
    try {
        String sql = "select name from users order by id";
        pstmt = con.prepareStatement(sql);
        rs = pstmt.executeQuery();
        while(rs.next()) {
            Vector row = new Vector();
            row.add(rs.getString(1));
            rowData.add(row);
        }
        return rowData;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    } finally {
        JDBCconn.closeConnection();
    }
}