private Object[] loadName;

public Object[] LoadSupplier(){
    b = a.openSession();
    b.beginTransaction();
    Query query = b.createQuery("FROM Supplier");
    @SuppressWarnings("unchecked")
    ArrayList<Supplier> load = (ArrayList<Supplier>) query.list();
    b.getTransaction().commit();
    b.close();
    for(Supplier supply : load){
        loadName = new Object[]{supply.getSupplierName()};
    }
    return loadName;
}

comboCategory = new JComboBox(LoadSupplier());