@Entity
@Table(name="COURSES")
public class Course implements Serializable{
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue
	@Column(name="ID_COURSE")
	private int id;
	@Column(name="name")
	private String name;
	@Column(name="owner")
	private String owner;
	@Column(name="category")
	private String category;
	@Column(name="subscribes")
	private ArrayList<User> subscribes= new ArrayList<User>();
	@Column(name="attendee")
	private ArrayList<User> attendee= new ArrayList<User>();
	@Column(name="grade")
	private ArrayList<Integer> grade= new ArrayList<Integer>( );
	@Column(name="description")
	private String description;
	@Column(name="links")
	private String links;

 Course course = courseService.read(courseId);
			ArrayList<Integer> listGrades =( ArrayList<Integer>)  course.getGrade();
			//listGrades.add(grade);
		 	listGrades.add(2);
		 	listGrades.add(2);	 
			course.setGrade(listGrades);
			courseService.update(course);