delete element from xml file

I want to delete an element from xml-file. this is my code but the file dosen't change when I test it.

public static String supp(){

            try{

            racine=document.getRootElement();

            Element rac=racine.getChild("voitures");

               List   listelt = rac.getChildren();

                  int ok=1;

               Iterator i = listelt.iterator();

             while(i.hasNext()&& ok==1)

           {

               Element courrent = (Element)i.next();

               if (courrent.getAttribute("immatricule").getValue().equals("8345 tU 125")){

                   System.out.println(" "+courrent.getAttribute("immatricule").getValue());

                     //Element free = (Element)courrent.detach();

                    System.out.println(rac.getName());

                    rac.removeContent(courrent);

                     ok=0;

                     //courrent.removeChild(couleur);

                     System.out.println("supprimé");

               }

           }}catch(Exception e){return e.getMessage();}