code: public void setHost(String host) {
  		if(isModifiable == ModifiableRule.ContactSystem || isModifiable == ModifiableRule.NotModifiable) {
  			throw new IllegalArgumentException("Host part of the URI is not modifiable");
  		}
  		try {
  			getSipURI().setHost(host);
  		} catch (ParseException e) {
  			logger.error("parse exception occured", e);
  			throw new IllegalArgumentException("Bad arg!",e);
  		}
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipURI#setHost(java.lang.String)