docs: public final boolean contains(char[] a) {
          final int last_pos = off + len - a.length;
          outer:
          for (int pos = off; pos <= last_pos; ++pos) {
              for (int a_off = 0; a_off < a.length; ++a_off) {
                  if (a[a_off] != fb[pos + a_off]) {
                      continue outer;
                  }
              }
              return true;
          }
          return false;
      }