ByteUtil { public static byte[] setBit(byte[] data, int pos, int val) { if ((data.length * 8) - 1 < pos) throw new Error("outside byte array limit, pos: " + pos); int posByte = data.length - 1 - (pos) / 8; int posBit = (pos) % 8; byte setter = (byte) (1 << (posBit)); byte toBeSet = data[posByte]; byte result; if (val == 1) result = (byte) (toBeSet | setter); else result = (byte) (toBeSet & ~setter); data[posByte] = result; return data; }  static byte[] appendByte(byte[] bytes, byte b); static byte[] bigIntegerToBytes(BigInteger b, int numBytes); static byte[] bigIntegerToBytes(BigInteger value); static int matchingNibbleLength(byte[] a, byte[] b); static byte[] longToBytes(long val); static byte[] longToBytesNoLeadZeroes(long val); static byte[] intToBytes(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 byte[] encodeValFor32Bits(Object arg); static byte[] encodeDataList(Object... args); 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[] merge(byte[]... arrays); static boolean isNullOrZeroArray(byte[] array); static boolean isSingleZero(byte[] array); static Set<byte[]> difference(Set<byte[]> setA, Set<byte[]> setB); static int length(byte[]... bytes); static final byte[] EMPTY_BYTE_ARRAY; static final byte[] ZERO_BYTE_ARRAY; }
@Test public void setBitTest() { byte[] data = ByteBuffer.allocate(4).putInt(0).array(); int posBit = 24; int expected = 16777216; int result = -1; byte[] ret = ByteUtil.setBit(data, posBit, 1); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); posBit = 25; expected = 50331648; ret = ByteUtil.setBit(data, posBit, 1); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); posBit = 2; expected = 50331652; ret = ByteUtil.setBit(data, posBit, 1); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); posBit = 24; expected = 33554436; ret = ByteUtil.setBit(data, posBit, 0); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); posBit = 25; expected = 4; ret = ByteUtil.setBit(data, posBit, 0); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); posBit = 2; expected = 0; ret = ByteUtil.setBit(data, posBit, 0); result = ByteUtil.byteArrayToInt(ret); assertTrue(expected == result); }