Hibernate One-To-Many&Many-To-One Mapping

@Entity
@Table(name="x_Group")
public class Group {
    private int id;
    private String name;
    //for one-to-many illustration
    private Set<User> users=new HashSet<User>();
    
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    
    @OneToMany(mappedBy="group")
    public Set<User> getUsers() {
        return users;
    }

    public void setUsers(Set<User> users) {
        this.users = users;
    }
 
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }    
}

@Entity
@Table(name="x_user")
public class User {
   private int id;
   private String name;
   private Group group;
       
   @ManyToOne
    public Group getGroup() {
        return group;
    }

    public void setGroup(Group group) {
        this.group = group;
    }

    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

<hibernate-mapping package="com.hibernate.model">
<class name="User" table ="U_User">
   <id name="id"></id>
    <property name="name"></property>
    <!-- column="xx" xx must be same as key column ="xx" of Group-->
    <many-to-one name="group" column="groupId" >
   </many-to-one>
</class>

</hibernate-mapping>


<hibernate-mapping package="com.hibernate.model">
<class name="Group" table="T_Group">
   <id name="id"></id>
    <property name="name"></property>
    <set name="users">
      <key column="groupId"></key>
      <one-to-many class="com.hibernate.model.User"/>
    </set>
</class>