### Question:
ConvertUtils { public static String reverseHexString(String hex) { final StringBuilder builder = new StringBuilder(hex.length()); for (int i = hex.length(); i > 1; i -= 2) { builder.append(hex, i - 2, i); } return builder.toString(); } private  ConvertUtils(); static byte[] getBytes(final String hexString); static String toHex(final byte[] bytes); static String padHex(final String hex, int hexStringSize); static byte[] fromHexToBytes(String hexString); static Pair<String, Integer> xorValues(String originalValue, String newValue); static String fromHexToString(final String hexString); static String fromStringToHex(final String plainText); static String toSize16Hex(final BigInteger number); static void validateNotNegative(final BigInteger number); static void validateNotNegative(final long number); static String toString(final BigInteger number); static BigInteger toUnsignedBigInteger(long value); static BigInteger toUnsignedBigInteger(BigInteger value); static boolean isHexString(String input); static void validateIsHexString(String input); static void validateIsHexString(String input, Integer size); static String reverseHexString(String hex); static byte[] xor(byte[] b1, byte[] b2);  }### Answer:
@Test void reverseHexString() { Assertions.assertEquals("FF75", ConvertUtils.reverseHexString("75FF")); Assertions.assertEquals( "FF66FF66FF66FF66FF66FF66FF66FF75FF75FF75FF75FF75FF75", ConvertUtils.reverseHexString("75FF75FF75FF75FF75FF75FF66FF66FF66FF66FF66FF66FF66FF")); }
@Test void reverseHex() { String hex = "D9E338F78767ED95"; String reverseHex = ConvertUtils.reverseHexString(hex); Assertions.assertEquals("95ED6787F738E3D9", reverseHex); Assertions.assertEquals(hex, ConvertUtils.reverseHexString(reverseHex)); }