docs: public static String[] subtraction(String[] arr1, String[] arr2) {
          if (arr1 == null || arr1.length == 0 || arr2 == null || arr2.length == 0) {
              return arr1;
          }
          List<String> list = new ArrayList<String>(Arrays.asList(arr1));
          list.removeAll(Arrays.asList(arr2));
          return list.toArray(new String[0]);
      }