出错，为什么我只有Get方法可以运行？其他三个方法都报错
@Test
public void testGetStudents(){
Students s = (Students) session.get(Students.class, 1);
System.out.println(s.getClass().getName());
}
public void testLoadStudents(){
Students s = (Students) session.load(Students.class, 1);
System.out.println(s);
}
public void testUpdateStudents(){
Students s = (Students) session.get(Students.class, 1);
s.setGender("女");
session.update(s);
}
public void testDeleteStudents(){
Students s = (Students) session.get(Students.class, 1);
session.delete(s);
}
