Print the Object Adress with Hashcode and returns Null

class Student{
int rollno;
int marks;
Student(){
rollno=1001;
marks=75;
}
public String toString(){
System.out.println(getClass().getName()+"@"+Integer.toString(hashCode()));
return null;
}
}
public class TestingExample {

/**
* @param args
*/
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
Student s=new Student();
System.out.println(s);
}
}