### Question:
HllV4 { public boolean pfAdd(byte[] element) { return hllhdr.hllAdd(element); } HllV4(byte[] representation);   HllV4(); long pfCount(); boolean pfAdd(byte[] element); HllV4 pfMerge(HllV4... others); byte[] dumpRepr(); static HllV4Builder newBuilder();  }### Answer:
@Test public void testPfAdd() { HllV4 hll = HllV4.newBuilder().build(); for (int i = 1; i <= 1000; i++) { hll.pfAdd(String.valueOf(i).getBytes(StandardCharsets.UTF_8)); } assertThat(hll.pfCount()).isEqualTo(1001L); hll.pfAdd("1001".getBytes(StandardCharsets.UTF_8)); assertThat(hll.pfCount()).isEqualTo(1002L); }