### Question:
HexUtil { public static String toHexFromByte(final byte b) { byte leftSymbol = (byte) ((b >>> BITS_PER_HEX_DIGIT) & 0x0f); byte rightSymbol = (byte) (b & 0x0f); return (hexSymbols[leftSymbol] + hexSymbols[rightSymbol]); }  static String toHexFromByte(final byte b); static byte toByteFromHex(char upperChar, char lowerChar); static String toHexFromBytes(final ByteBuffer bytes); static String toHexFromBytes(final byte[] bytes); static byte[] toBytesFromHex(String hexStr); final static int BITS_PER_HEX_DIGIT; }### Answer:
@Test public void testHexToByte() { Assert.assertEquals("00", HexUtil.toHexFromByte((byte)0x00)); Assert.assertEquals("01", HexUtil.toHexFromByte((byte)0x01)); Assert.assertEquals("02", HexUtil.toHexFromByte((byte)0x02)); Assert.assertEquals("03", HexUtil.toHexFromByte((byte)0x03)); Assert.assertEquals("04", HexUtil.toHexFromByte((byte)0x04)); Assert.assertEquals("05", HexUtil.toHexFromByte((byte)0x05)); Assert.assertEquals("06", HexUtil.toHexFromByte((byte)0x06)); Assert.assertEquals("07", HexUtil.toHexFromByte((byte)0x07)); Assert.assertEquals("08", HexUtil.toHexFromByte((byte)0x08)); Assert.assertEquals("09", HexUtil.toHexFromByte((byte)0x09)); Assert.assertEquals("0a", HexUtil.toHexFromByte((byte)0x0a)); Assert.assertEquals("0b", HexUtil.toHexFromByte((byte)0x0b)); Assert.assertEquals("0c", HexUtil.toHexFromByte((byte)0x0c)); Assert.assertEquals("0d", HexUtil.toHexFromByte((byte)0x0d)); Assert.assertEquals("0e", HexUtil.toHexFromByte((byte)0x0e)); Assert.assertEquals("0f", HexUtil.toHexFromByte((byte)0x0f)); Assert.assertEquals("23", HexUtil.toHexFromByte((byte)0x23)); Assert.assertEquals("19", HexUtil.toHexFromByte((byte)0x19)); Assert.assertEquals("75", HexUtil.toHexFromByte((byte)0x75)); Assert.assertEquals("43", HexUtil.toHexFromByte((byte)0x43)); Assert.assertEquals("a9", HexUtil.toHexFromByte((byte)0xa9)); Assert.assertEquals("3b", HexUtil.toHexFromByte((byte)0x3b)); Assert.assertEquals("c3", HexUtil.toHexFromByte((byte)0xc3)); Assert.assertEquals("ff", HexUtil.toHexFromByte((byte)0xff)); }