public static void main(String[] args) {
        java.util.Random r = new java.util.Random();
        Bits bits = new Bits();
        int dupCount = 0;
        for (int i=0; i<125; i++) {
            int k;
            do {
                k = r.nextInt(250);
            } while (bits.isMember(k));
            System.out.println("adding " + k);
            bits.incl(k);
        }
        int count = 0;
        for (int i = bits.nextBit(0); i >= 0; i = bits.nextBit(i+1)) {
            System.out.println("found " + i);
            count ++;
        }
        if (count != 125) throw new Error();
    }