MergeSort with Comparable and Lists

Hello guys!

I have big problem with mergesort in Java. I can't figure out why it do not works.

I need write it on lists using Comparable. Here is piece of code:

Java Code:

class MergeSort{
  Comparator _comparator;
  List lista = new ArrayList<>();
  List list_temp = new ArrayList<>();



MergeSort(Comparator comparator){
    _comparator = comparator;
}
void sort(List lista){
    this.lista = lista;

    mergesort(0, lista.size()-1);

}

void mergesort(int start, int end){
   if(start < end){
       int mid = start + (end-start)/2;

       mergesort(start, mid);
       mergesort(mid+1, end);

       merge (start, mid, end);
   }


}

void merge(int start, int mid, int end){

    int i = start;
    int j = mid + 1;
    int k = start;

    for(int h = start; h <= end; h++)
        list_temp.add(lista.get(h));

   while (i <= mid && j <= end) {
        if (_comparator.compare(list_temp.get(i),list_temp.get(j)) <= 0) {
            lista.set(k, list_temp.get(i)); 
            i++;
        } 
        else{
            lista.set(k, list_temp.get(j));  
            j++;
        }
       k++;

    while (i <= mid) {
        lista.set(k, list_temp.get(i));  
        k++;
        i++;
    }
    }



  }

 final class NaturalComparator implements Comparator{
          public static final NaturalComparator INSTANCE = new NaturalComparator();

          NaturalComparator(){}

         @Override
          public int compare(Object left, Object right) throws ClassCastException{
                  return ((Comparable) left).compareTo(right);
          }
}

I have tried everything, still no results. It's return list with random placed numbers.

Thnak you for any advice!