import java.sql.*;
import java.io.*;
import java.util.*;
//import org.gjt.mm.mysql.Driver;

public class TestDB {

public static void main(String[] args) {
try
{
Connection conn=getConnection();
Statement stat=conn.createStatement();

stat.execute("CREATE TABLE Greetings (Name CHAR(20))");
stat.execute("INSERT INTO Greetings VALUES('Hello,World!')");

ResultSet result=stat.executeQuery("SELECT * FROM Greetings");
result.next();
System.out.println(result.getString(1));
result.close();

stat.execute("DROP TABLE Greetings");

stat.close();
conn.close();
}
catch(SQLException ex)
{
while(ex!=null)
{
ex.printStackTrace();
ex=ex.getNextException();
}
}
catch(IOException ex)
{
ex.printStackTrace();
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
catch(InstantiationException e)
{
e.printStackTrace();
}
catch(IllegalAccessException e)
{
e.printStackTrace();
}
}

public static Connection getConnection() throws SQLException,IOException,ClassNotFoundException,InstantiationException,IllegalAccessException
{
String driver="org.gjt.mm.mysql.Driver";
Class.forName(driver).newInstance();
String url="jdbc:mysql:test";
String username="root";
String password="840104";

return DriverManager.getConnection(url,username,password);
}
}

classpath也设置了，在.java目录下也放了解压后的org.*的东西，
但是运行的时候总是报告
java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getConnection(DriverManager.java:545)
at java.sql.DriverManager.getConnection(DriverManager.java:171)
at TestDB.getConnection(TestDB.java:78)
at TestDB.main(TestDB.java:17)
请问为什么？