struts中调用接口时候的Cannot make a static reference to the non-static method问题

用struts想实现一个注册的功能，注册成功就跳转到success的页面，失败就跳回到注册页面写了一段DAO：public interface AddStudentDAO {public boolean addStudent(AddStudentForm studentForm);}实现DAO的方法：public class Student implements AddStudentDAO {@Overridepublic boolean addStudent(AddStudentForm studentForm) {return false;}}action的代码：public class AddStudentAction extends Action {@Overridepublic ActionForward execute(ActionMapping mapping, ActionForm form,HttpServletRequest request, HttpServletResponse response)throws Exception {//转型AddStudentForm addStudentForm=(AddStudentForm)form;//调用接口AddStudentDAO student=new AddStudentDAO(); boolean successful=false;successful=AddStudentDAO.addStudent(addStudentForm); //关键字String returnURLKeyWord = "addFailure";if(successful == true){returnURLKeyWord = "addSuccess";}return mapping.findForward(returnURLKeyWord);}}调用接口部分报错，我是按教学视频中来的，视频中DAO这个接口实例化了。。。如果我把//调用接口AddStudentDAO student=new AddStudentDAO();boolean successful=false;successful=AddStudentDAO.addStudent(addStudentForm);改成 Student student=new Student();boolean successful=false;successful=AddStudentDAO.addStudent(addStudentForm);最后的那行successful=AddStudentDAO.addStudent(addStudentForm)还是报错，Cannot make a static reference to the non-static method如果在Student类中把addStudent方法变成static的，那又会提示Illegal modifier for the interface method addStudent; only public & abstract are permitted大家指点指点