code: public UnicodeSet complement() {
          checkFrozen();
          if (list[0] == LOW) {
              System.arraycopy(list, 1, list, 0, len-1);
              --len;
          } else {
              ensureCapacity(len+1);
              System.arraycopy(list, 0, list, 1, len);
              list[0] = LOW;
              ++len;
          }
          pat = null;
          return this;
      }
docs: This is equivalent to
  <code>complement(MIN_VALUE, MAX_VALUE)</code>.