java - Finding uppercase in linkedlist and returning new linkedlist with found elements? -

i have write method search linkedlist(listnode, cointaining 1 char per listnode), finding uppercase chars, copy them new listnode , returning new listnode. code far, fails junit testing (provided prof.)

this list node:

public class listnode {     public char element;     public listnode next;  } 

and method ive wrote, dont seem work:

 public static listnode copyuppercase(listnode head) {      listnode newlistnode = mkempty();     if(head == null){         throw new listsexception("lists: null passed copyuppercase");     }else{         char[] sss = tostring(head).tochararray();         for(int = 0; < sss.length ; i++ )                 if(character.isuppercase(sss[i])){                     newlistnode.element = sss[i];                        }                 newlistnode = newlistnode.next;         }                return newlistnode; } 

what worng code? why fail?

expanding on @enterbios's answer (+1 him), try following:

public static listnode touppercase(listnode head) {     if (head == null)         throw new listsexception("lists: null passed copyuppercase");      listnode newhead = null;     listnode current = null;      char[] sss = tostring(head).tochararray();      (int i=0; i<sss.length; i++) {         if (character.isuppercase(sss[i])) {             if (current == null) {                 current = mkempty();                 newhead = current;             } else {                 current.next = mkempty();                 current = current.next;             }             current.element = sss[i];         }     }     return newhead;  }