@Entity
@Table(name = "Users")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class User implements Serializable {

    @Id
    @Column(name = "UserID", unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long userId;
}

@Entity
@Table(name = "Tasks")
public class Task implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "TaskID", unique = true, nullable = false)
    private Long taskId;


    @OneToMany(mappedBy = "task", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<UserTask> users;
}

@Entity
@Table(name = "RegularUsers")
public class RegularUser extends User {

    @OneToMany(mappedBy = "regularUser", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<UserTask> tasks;
}

@Entity
@Table(name = "UserTask")
public class UserTask implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "UserTaskID", unique = true, nullable = false)
    private Long userTaskId;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "UserID_FK", referencedColumnName = "UserID")
    private RegularUser regularUser;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "TaskID_FK", referencedColumnName = "TaskID")
    private Task task;
}

@JoinColumn(name = "UserID_FK", referencedColumnName = "UserID")
    private RegularUser regularUser;

Hibernate: 
    
    create table RegularUsers (
       UserID numeric(19,0) not null,
        primary key (UserID)
    )
Hibernate: 
    
    create table Tasks (
       TaskID numeric(19,0) not null,
        primary key (TaskID)
    )
Hibernate: 
 create table UserTask (
       UserTaskID numeric(19,0) not null,
        UserID_FK numeric(19,0),
        TaskID_FK numeric(19,0),
        primary key (UserTaskID)
    )
Hibernate:     
       alter table RegularUsers 
       add constraint UK_n68f0rf3bjbec7ril2q103g10 unique (UserID)
Hibernate: 
       alter table UserTask 
       add constraint FKiguctfwkdscbv8l409lnbcfna 
       foreign key (TaskID_FK) 
       references Tasks