public String getImg(String s) {
 int index1 = s.lastIndexOf("[img]");      
 int index2 = s.lastIndexOf("[\\img]");
 if (index1 == -1 || index2 == -1 || index1 > index2) 
     return null;
 return s.substring(index1, index2 + "[\\img]".length()); }