插入对大量数据进行排序

Question

我写了这个版本的插入排序算法，它允许用户选择升序排序还是排序降序。我在2000万的Integer上试过它，但它真的很慢。我该如何改进呢？

public Sorting insertionSort(int ordinamento) throws SortingException {
    if (ordinamento != 0 && ordinamento != 1) throw new SortingException("ERRORE!");
    for(int i=1; i<(this.array).size(); i++){
      T elem=(this.array).get(i);
      int j=i-1;
      if (ordinamento == 0) { 
        while(j>=0 && (this.comparator).compare(elem, (this.array).get(j))<0){
          (this.array).set(j+1, (this.array).get(j));
          j--;
        }
      } else {
        while(j>=0 && (this.comparator).compare(elem, (this.array).get(j))>0){
          (this.array).set(j+1, (this.array).get(j));
          j--;
        }
      }
      (this.array).set(j+1, elem);
    }
    return this;
  }

类结构是这样的：

public Sorting(Comparator<? super T> comparator) {
   this.array = new ArrayList<>();
   this.comparator = comparator;