code: public int compareTo(int sortKey, ArrayListWithSortableKey<E> that) {
  		this.setSortKey(sortKey);
  		that.setSortKey(sortKey);
  		return this.compareTo(that);
  	}
docs: Sets the {@code sortKey} for {@code this} and {@code that} and then calls
  {@code this.compareTo(that)}
  
  @param sortKey
  The column to be used as the sortKey
  @param that
  The {@code ArrayListWithSortableKey} to be compared
  @return Same as {@link #compareTo(ArrayListWithSortableKey)} after
  applying the sortKey to {@code this} and {@code that}