BitcoinUtil { public static byte[] convertLongToByteArray(long longToConvert) { return ByteBuffer.allocate(8).putLong(longToConvert).array(); } private  BitcoinUtil(); static long convertSignedIntToUnsigned(int signedInt); static byte[] convertIntToByteArray(int intToConvert); static byte[] convertLongToByteArray(long longToConvert); static byte[] convertBigIntegerToByteArray(BigInteger bigIntegerToConvert,int exactArraySize); static byte[] convertVarIntByteBufferToByteArray(ByteBuffer byteBuffer); static long convertVarIntByteBufferToLong(ByteBuffer byteBuffer); static BigInteger getVarIntBI(byte[] varInt); static long getVarInt(byte[] varInt); static byte getVarIntSize(byte firstByteVarInt); static long getSize(byte[] byteSize); static byte[] reverseByteArray(byte[] inputByteArray); static byte[] convertHexStringToByteArray(String hexString); static String convertByteArrayToHexString(byte[] byteArray); static Date convertIntToDate(int dateInt); static boolean compareMagics(byte[] magic1,byte[] magic2); static byte[] getTransactionHash(BitcoinTransaction transaction); static byte[] getTransactionHashSegwit(BitcoinTransaction transaction);  }
@Test public void convertLongToByteArray() { byte[] longByteArray = BitcoinUtil.convertLongToByteArray(1L); byte[] comparatorArray = new byte[]{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01}; assertArrayEquals( comparatorArray,longByteArray,"1 in int must be equivalent to the array {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01}"); }