public List<String> extrahiereDuplikate(List<String> woerter)
    {
        int laenge = woerter.size();
        boolean[] duplikate = new boolean[laenge];
        for (int i =0;i<laenge;i++){
            for (int j=1+i;j<laenge;j++){
                String str1 = woerter.get(i);
                String str2 = woerter.get(j);
                if(str1==str2){
                    duplikate[i]=true;
                    duplikate[j]=true;
                }
            }
        }
        List<String> dupes = new LinkedList();
        for (int i=0;i<laenge;i++){
            if (duplikate[i] && !dupes.contains(woerter.get(i))){
                dupes.add(woerter.get(i));

            }
        }
        return dupes;