public String serializeToString() {
        final StringBuilder answer = new StringBuilder();
        final LongIterator i = this.getLongIterator();
        while (i.hasNext()) {
            long nextValue = i.next();
            if (answer.length() > 0) {
                answer.append(",");
            }
            answer.append(signedLongs ? nextValue : toUnsignedString(nextValue));
        }
        return answer.toString();
    }
@Test
    public void testSerializeToString() {
        Assert.assertEquals("0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19", largeBitmap.serializeToString());
    }