andNot not working as expected

[nigel-v-thomas]

Hey, Thanks for sharing this code, really helpful! Just a quick observation about the andNot method. This function fails to pass the following test:

        bitSet = new BitSet();
        BitSet bs = bitSet;
        for (int i = 0; i <= 7; i++) {
             bitSet.set(i);
        }
        bs.clear(5);
        BitSet bs2 = new BitSet();
        bs2.set(2);
        bs2.set(3);
        bs.andNot(bs2);
        assertEquals("Incorrect bitset after andNot",
                "{0, 1, 4, 6, 7}", bs.toString());
        bs = new BitSet(0);
        bs.andNot(bs2);
        assertEquals("Incorrect size", 0, bs.length());

Fails assertion with "incorrect bitset after andNot", I see "{0,1,2,3,4,6,7}" instead of "{0, 1, 4, 6, 7}" I have moved to using this implementation as well : https://github.com/atonparker/bitterset