code: public void setQ(float q) {
  		if(q == -1.0) {
  			this.removeParameter(Q_PARAM_NAME);
  			return;
  		}
  		if(q > 1.0 || q < 0) {
  			throw new IllegalArgumentException("the new qvalue isn't between 0.0 and 1.0 (inclusive) and isn't -1.0.");
  		}
  		this.setParameter(Q_PARAM_NAME, Float.toString(q));
  		/*
  		try {
  			Parameters uri = (Parameters) this.address.getURI();
  			uri.setParameter(Q_PARAM_NAME, Float.toString(q));
  		} catch (ParseException ex) {
  			throw new IllegalArgumentException("Bad parameter", ex);
  		}*/
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.Address#setQ(float)