code: public static IntSet and (IntSet... sets)
      {
          checkNotNull(sets);
          IntSet result = create();
          int len = sets.length;
          if (len > 0) {
              OUTER:
              for (Interator it = sets[0].interator(); it.hasNext(); ) {
                  int val = it.nextInt();
                  for (int ii = 1; ii < len; ii++) {
                      if (!sets[ii].contains(val)) {
                          continue OUTER;
                      }
                  }
                  result.add(val);
              }
          }
          return result;
      }
docs: Create a new IntSet containing the ints that are contained in <b>all</b>
  of the specified sets. The returned set may be further modified per your needs.