### Question:
ByteUtil { public static byte[] parseBytes(byte[] input, int offset, int len) { if (offset >= input.length || len == 0) { return EMPTY_BYTE_ARRAY; } byte[] bytes = new byte[len]; System.arraycopy(input, offset, bytes, 0, Math.min(input.length - offset, len)); return bytes; } private  ByteUtil(); static byte[] appendByte(byte[] bytes, byte b); static byte[] cloneBytes(byte[] bytes); static byte[] bigIntegerToBytes(BigInteger b, int numBytes); static byte[] bigIntegerToBytes(BigInteger value); static byte[] parseBytes(byte[] input, int offset, int len); static int matchingNibbleLength(byte[] a, byte[] b); static byte[] longToBytes(long val); static byte[] longToBytesNoLeadZeroes(long val); static byte[] intToBytes(int val); static byte[] intToBytesNoLeadZeroes(int val); static String toHexString(byte[] data); static byte[] calcPacketLength(byte[] msg); static int byteArrayToInt(byte[] b); static long byteArrayToLong(byte[] b); static String nibblesToPrettyString(byte[] nibbles); static String oneByteToHexString(byte value); static int numBytes(String val); static int firstNonZeroByte(byte[] data); static byte[] stripLeadingZeroes(byte[] data); static boolean increment(byte[] bytes); static byte[] copyToArray(BigInteger value); static ByteArrayWrapper wrap(byte[] data); static byte[] setBit(byte[] data, int pos, int val); static int getBit(byte[] data, int pos); static byte[] and(byte[] b1, byte[] b2); static byte[] or(byte[] b1, byte[] b2); static byte[] merge(byte[]... arrays); static boolean isSingleZero(byte[] array); static boolean isAllZeroes(byte[] array); static Set<T> difference(Set<T> setA, Set<T> setB); static int length(byte[]... bytes); static short bigEndianToShort(byte[] bs); static short bigEndianToShort(byte[] bs, int off); static byte[] shortToBytes(short n); static int numberOfLeadingZeros(byte[] bytes); static byte[] leftPadBytes(@Nonnull byte[] original, int newLength); static boolean fastEquals(byte[] left, byte[] right); static final byte[] EMPTY_BYTE_ARRAY; }### Answer:
@Test public void testParseBytes() { byte[] shortByteArray = new byte[]{0,1}; byte[] normalByteArray = new byte[]{0,1,2,3,4,5}; byte[] normalByteArrayOffset3LeadingZeroes = new byte[]{3,4,5,0,0,0}; byte[] b1 = ByteUtil.parseBytes(shortByteArray, shortByteArray.length+1, 10); assertEquals(b1,ByteUtil.EMPTY_BYTE_ARRAY); byte[] b2 = ByteUtil.parseBytes(shortByteArray, shortByteArray.length-1, 0); assertEquals(b1,ByteUtil.EMPTY_BYTE_ARRAY); byte[] b3 = ByteUtil.parseBytes(normalByteArray, normalByteArray.length -3, normalByteArrayOffset3LeadingZeroes.length); for (int i=0; i < b3.length; i++) { assertEquals(b3[i],normalByteArrayOffset3LeadingZeroes[i]); } }