if (prop.equals(m_roles[0])) { return m_roles[1]; } else { return m_roles[0]; }
if (prop.equals(m_roleOne)) { return m_roleTwo; } else if (prop.equals(m_roleTwo)) { return m_roleOne; } else { throw new IllegalArgumentException ("property not in association: " + prop); }
    public Property getAssociatedProperty(Property prop) {        if (prop.equals(m_roles[0])) {            return m_roles[1];        } else {            return m_roles[0];        }    }