求帮忙！

[楚靖靖]

package Water;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class QueryDesc {



public static List<UserVo> showUser(String M ) throws ClassNotFoundException{


Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
List<UserVo> list = new ArrayList<UserVo>();//声明一个List集合，用于存放查询出的数据

try {

String Str=null;
Str=String.format(" %s ","str"); // 格式化字符串


conn = JDBC_Connection.getConnection();// 连接数据库
stmt = conn.createStatement();// 建立Statement对象;
rs = stmt.executeQuery("select %s from MONTHAVERAGE" );

while(rs.next())// 结果集存在，则进行循环遍历
{

UserVo userVo = new UserVo();
userVo.setDD(rs.getInt("dd"));
list.add(userVo);

}

}catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBC_Connection.free(rs, conn, stmt);// 关闭连接
}
return list;
}

public static void main(String[] args) throws ClassNotFoundException {
System.out.print("请输入要计算的月份:");
Scanner scanner=new Scanner(System.in);
String str=scanner.next();

List<UserVo> list=QueryDesc.showUser(str);//调用查询方法
//如果list集合不为空，则循环遍历打印出所有的信息
if(list!=null){
System.out.print("dd");
System.out.println();
for (int j = 0; j < list.size(); j++) {

System.out.print(list.get(j).getDD()+"\t");
System.out.println();
}
}



}

}
为什么总是显示无效字符啊？

[中华雪碧]

UserVo的代码 和完整的报错信息

[楚靖靖]

package Water; public class UserVo { private double dd; public double getDD() { return dd; } public void setDD(double dd) { this.dd = dd; } } 以上是UserVo的代码 以下是执行后的情况，谢谢啦！ 创建驱动成功！ 连接数据库成功！ java.sql.SQLException: 列名无效 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111) at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:145) at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:207) at oracle.jdbc.driver.OracleStatement.getColumnIndex(OracleStatement.java:3295) at oracle.jdbc.driver.OracleResultSetImpl.findColumn(OracleResultSetImpl.java:1913) at oracle.jdbc.driver.OracleResultSet.getInt(OracleResultSet.java:1562) at Water.QueryDesc.showUser(QueryDesc.java:38) at Water.QueryDesc.main(QueryDesc.java:57) dd

[dushouxian]

rs = stmt.executeQuery("select %s from MONTHAVERAGE" ); 改成 rs = stmt.executeQuery("select dd from MONTHAVERAGE" );

[楚靖靖]

请输入要计算的月份:一 创建驱动成功！ 连接数据库成功！ java.sql.SQLException: ORA-00904: "DD": 标识符无效 at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111) at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:330) at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:287) at oracle.jdbc.driver.T4C8Oall.receive(T4C8Oall.java:744) at oracle.jdbc.driver.T4CStatement.doOall8(T4CStatement.java:206) at oracle.jdbc.driver.T4CStatement.executeForDescribe(T4CStatement.java:800) at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1038) at oracle.jdbc.driver.T4CStatement.executeMaybeDescribe(T4CStatement.java:840) at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1133) at oracle.jdbc.driver.OracleStatement.executeQuery(OracleStatement.java:1273) at Water.QueryDesc.showUser(QueryDesc.java:33) at Water.QueryDesc.main(QueryDesc.java:59) dd 以上是执行结果

[yangzhiyong1314]

rs = stmt.executeQuery("select dd from MONTHAVERAGE dd" ); 或者rs = stmt.executeQuery("select * from MONTHAVERAGE " );

[楚靖靖]

按照5楼那样改还是不行