public static String toLowerHex(long v) {
    char[] data = RecyclableBuffers.parseBuffer();
    writeHexLong(data, 0, v);
    return new String(data, 0, 16);
  }
@Test void toLowerHex_fixedLength() {
    assertThat(toLowerHex(0L)).isEqualTo("0000000000000000");
  }