JDBC executeQuery问题
import java.sql.*;
import java.util.*;
import java.io.*;
public class Charu {

public String driver;
Connection conn;
public String pass;
public String user;
public String url;
Statement sta;

public void ininpram(String wenjian) throws IOException
{
Properties props=new Properties();
props.load(new FileInputStream(wenjian));
driver=props.getProperty("driver");

pass=props.getProperty("pass");
user=props.getProperty("user");
url=props.getProperty("url");




}
public ResultSet inser(String sql) throws Exception
{ try
{
// Class.forName(driver);
//conn=DriverManager.getConnection(url,user,pass);
Class.forName(driver);
conn=DriverManager.getConnection(url,user,pass);
sta=conn.createStatement();
ResultSet re=sta.executeQuery(sql);
return re;
}
finally{

if(sta!=null)
{
sta.close();
}
if(conn!=null)
{
conn.close();
}
}
}
public static void main(String[] args) throws Exception
{
Charu ed=new Charu();

ResultSet res=ed.inser("select * from student");
while (res.next())
{
System.out.println(res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t"+
res.getInt(1)+"\t");
}

}

}


用eclipe提示

Exception in thread "main" java.lang.NullPointerException
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at Charu.inser(Charu.java:32)
at Charu.main(Charu.java:54)


[解决办法]
没找到驱动类，加入jar包
[解决办法]
空指针异常，我建议你检查一下配置文件，配置文件的读取代码有问题，配置文件的路径名你都没穿进去，如果代码是你抄的书上的，我建议你仔细对一对，
[解决办法]
估计是配置文件的问题。

Java code

Properties props=new Properties();    props.load(new FileInputStream(wenjian));  // 这里wenjian路径对了没？driver=props.getProperty("driver");