class aclass = class.forname(xxx.xx.xx);
object aninstance = aclass.newinstance();
class.forname("").newinstance()返回的是object
but there is some limit for this method to create instance
that is your class constructor should no contain parameters, 
and you should cast the instance manually.
class driver{
protected static driver current;
public static driver getdriver(){
return current;
}
}
class mydriver extends driver{
static{
driver.current=new mydriver();
}
mydriver(){}
                        }

class.forname("mydriver");
            driver d=driver.getdriver();c

public class myjdbcdriver implements driver {
static {
drivermanager.registerdriver(new myjdbcdriver());
}
            }