@Entity
@Table(name = "HOLIDAYPACKAGE")
public final class HolidayPackage {
   private Integer idPackage;
   private String name;
   
   private Set<HolidayPackageVariant> holidayPackageVariants = new HashSet<HolidayPackageVariant>(0);
   
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "IDHOLIDAYPACKAGE", nullable = false)
   public Integer getIdPackage() {
      return idPackage;
   }
   
   @OneToMany(fetch=FetchType.LAZY, cascade={CascadeType.ALL}, mappedBy = "holidayPackage")
   public Set<HolidayPackageVariant> getHolidayPackageVariants() {
      return holidayPackageVariants;
   }
   
   // ommitted other part of the code
   }
   
@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@Table(name="HOLIDAYPACKAGEVARIANT")
public abstract class HolidayPackageVariant {
   private Integer idHolidayPackageVariant;
   private HolidayPackage holidayPackage;
   private String typeHolidayPackage;
   
   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   @Column(name="IDHOLIDAYPACKAGEVARIANT", nullable=false)
   public Integer getIdHolidayPackageVariant() {
      return idHolidayPackageVariant;
   }

   @ManyToOne(fetch=FetchType.LAZY, cascade={CascadeType.ALL})
   @JoinColumn(name="IDHOLIDAYPACKAGE", nullable=false)
   public HolidayPackage getHolidayPackage() {
      return holidayPackage;
   }

   @Column(name="TYPEHOLIDAYPACKAGE", nullable=true)
   public String getTypeHolidayPackage() {
      return typeHolidayPackage;
   }
   
   // ommitted setters, equals hashCode
   }
   
@Entity
@Table(name="LANDHOLIDAYPACKAGEVARIANT")
public final class LandHolidayPackageVariant extends HolidayPackageVariant{
   private static final String LAND = "LAND";
   
   protected LandHolidayPackageVariant() {}

   public LandHolidayPackageVariant(HolidayPackage holidayPackage) {
      super(holidayPackage, LAND);
   }
   }
   
@Entity
@Table(name="FLIGHTHOLIDAYPACKAGEVARIANT")
public final class FlightHolidayPackageVariant extends HolidayPackageVariant{
   private static final String FLIGHT = "FLIGHT";
   private Destination originCity;
   
   protected FlightHolidayPackageVariant(){}

   public FlightHolidayPackageVariant(HolidayPackage holidayPackage,
         Destination originCity) {
      super(holidayPackage, FLIGHT);
      setOriginCity(originCity);
   }

   @ManyToOne(fetch=FetchType.LAZY, cascade={CascadeType.ALL})
   @JoinColumn(name="IDDESTINATION", nullable=false)
   public Destination getOriginCity() {
      return originCity;
   }
   
   // ommited other setters etc functions
   }