public class TbUser  implements java.io.Serializable {
//public abstract class TbUser {
     private short id;
     private short refContactAddrId;
     private short refUsercategoryId;
     private String firstnameC;
     private String middlenameC;
     private String lastnameC;
     private Integer userCodeI;
     private Set<TbAddress> tbAddresses = new HashSet();
     ...
     ...

    public void setTbAddresses(Set<TbAddress> tbAddresses) {
        this.tbAddresses = tbAddresses;
    }
       
    // added this proc to try to add address but is not working
    public void addTbAddress(TbAddress tbAddress){
        tbAddress.setTbUser(this);
        tbAddresses.add(tbAddress);
    }
}

public class TbBuyer extends TbUser {
     private short id;
     private String buyerNameC;
     private BigDecimal buyerPremiumR;
     .... 
     ....
    public void setBuyerNameC(String buyerNameC) {
        this.buyerNameC = buyerNameC;
    }
}
       
=============  code sniplets ==================

        TbBuyer tbBuyer = new TbBuyer();
        TbAddress tbAddress = new TbAddress();
        HibernateUtils hibernateUtils = new HibernateUtils();
       
        tbBuyer.setBuyerNameC("BuyerID");       
        tbBuyer.setFirstnameC("JOE");
       
        tbAddress.setStreetC("2 View Heights");
        // how to add address when the access is via TbUser class
        tbBuyer.addTbAddress(tbAddress);     
        hibernateUtils.saveOrUpdate(tbBuyer);