code: public ComparatorChain<E> setComparator(final int index, final Comparator<E> comparator) throws IndexOutOfBoundsException {
  		return setComparator(index, comparator, false);
  	}
docs: 替换指定位置的比较器，保持原排序方式
  
  @param index 位置
  @param comparator {@link Comparator}
  @return this
  @exception IndexOutOfBoundsException if index &lt; 0 or index &gt;= size()