Null pointerException while getting Primary Key(primitive datatype) in hibernate

Question

I'm getting Null Pointer Exception while retrieving Primary Key or Id of an Entity in Hibernate result query.

My Entity class:

@Entity
@Table(name="sample")
public class ccy{

@Id
@column(name = "S_ID")
private long id;

 2nd varibale and so on

when i write hibernate query to retrieve it causes Null pointer exception, my select query is:

long ID = 0;
String HQL = "select id from sample";
Query query = session.createQuery(HQL);
ID = (Long)query.uniqueResult(); //getting NullPointerException in this line
 return ID;

Any suggestions to avoid this exception? I'm stuck here. Any help would be much appreciated