code: public UnicodeSet compact() {
          checkFrozen();
          if (len != list.length) {
              int[] temp = new int[len];
              System.arraycopy(list, 0, temp, 0, len);
              list = temp;
          }
          rangeList = null;
          buffer = null;
          return this;
      }
docs: Reallocate this objects internal structures to take up the least
  possible space, without changing this object's value.