StringBuilder  sb = new StringBuilder();
StringBuffer  sb = new StringBuffer();
	private String concat(VTDNav vn){	    StringBuilder  sb = new StringBuilder();	    if (argCount()>=2){			Alist temp = argumentList;			while(temp!=null){				sb.append(temp.e.evalString(vn));				temp = temp.next;			}			return sb.toString();	    } else 	        throw new IllegalArgumentException		("concat()'s argument count is invalid");	}