### Question:
StringUtils { public static String byteToHexString(final byte[] bytes, final int start, final int end) { if (bytes == null) { throw new IllegalArgumentException("bytes == null"); } final StringBuilder s = new StringBuilder(); for (int i = start; i < end; i++) { s.append(String.format("%02x", bytes[i])); } return s.toString(); } private  StringUtils(); static String stringifyException(final Throwable e); static String byteToHexString(final byte[] bytes, final int start, final int end); static String byteToHexString(final byte[] bytes); static byte[] hexStringToByte(final String hex); static String escapeHtml(String str); static final String arrayAwareToString(Object o); static final String arrayToString(Object array); static final String showControlCharacters(String str); static String getRandomString(Random rnd, int minLength, int maxLength); static String getRandomString(Random rnd, int minLength, int maxLength, char minValue, char maxValue);  }### Answer:
@Test public void testHexArrayToString() { byte[] byteArray = new byte[]{1, -97, 49, 74 }; String hex = StringUtils.byteToHexString(byteArray); assertEquals("019f314a", hex); }