code: public void setURI(URI uri) {
  		if(SipServletMessageImpl.isSystemHeader(isModifiable)) {
  			throw new IllegalStateException("this Address is used in a context where it cannot be modified");
  		}
  		this.getAddress().setURI(((URIImpl) uri).uri);
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.Address#setURI(javax.servlet.sip.URI)