code: public void setDisplayName(String name) {
  		if(SipServletMessageImpl.isSystemHeader(isModifiable)) {
  			throw new IllegalStateException("this Address is used in a context where it cannot be modified");
  		}
  		try {
  			getAddress().setDisplayName(name);
  		} catch (ParseException e) {
  			throw new IllegalArgumentException("illegal name ", e);
  		}
  
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.Address#setDisplayName(java.lang.String)