### Question:
SignalUtil { public static byte sign(int by) { return (byte)(0xff & by); }  static int intFromTwoBytes(byte[] bytes); static byte[] fourBytesFromInt(int n); static byte[] twoBytesFromInt(int n); static int intFromFourBytes(byte[] bytes); static int unsign(byte by); static byte sign(int by); static byte[] joinBytesArrays(byte[]... args); static byte[] joinBytesArrays(List<byte[]> args); static int multipleOfFour(int start); static byte[] xor(byte[] a, byte[] b); static long computeCRC32(byte[] bytes); static long computeCRC32c(byte[] bytes); static byte[] flipBytes(byte[] bytes); static byte[] longToFourBytes(long l); static byte[] longToFourBytesFlip(long l); static byte[] longToBytes(long l); static byte[] padToMultipleOfFour(byte[] bytes); static long bytesToLong(byte[] l); static byte[] md5key(byte[] key); static byte[] hmacSha1(byte[] data, byte[] key); static ByteRange range(int a, int b); static byte[] copyRange(byte[] bytes,ByteRange range); static List<byte[]> split(byte[] data,int chunkSize); static byte[] randomBytes(int lgt);  }### Answer:
@Test public void testSignByte() { byte b = SignalUtil.sign(255); assertEquals(-1,b); b = SignalUtil.sign(0); assertEquals(0,b); b = SignalUtil.sign(254); assertEquals(-2,b); b = SignalUtil.sign(128); assertEquals(-128,b); b = SignalUtil.sign(192); assertEquals(-64,b); }