### Question:
RLP { public static byte[] encodeElement(byte[] srcData) { if (isNullOrZeroArray(srcData)) { return BYTES_SHORT_ITEM; } else if (isSingleZero(srcData)) { return srcData; } else if (srcData.length == 1 && (srcData[0] & 0xFF) < 0x80) { return srcData; } else if (srcData.length < SIZE_THRESHOLD) { byte length = (byte) (OFFSET_SHORT_ITEM + srcData.length); byte[] data = new byte[srcData.length + 1]; System.arraycopy(srcData, 0, data, 1, srcData.length); data[0] = length; return data; } else { int tmpLength = srcData.length; byte byteNum = 0; while (tmpLength != 0) { ++byteNum; tmpLength >>>= 8; } byte[] data = new byte[srcData.length + 1 + byteNum]; data[0] = (byte) (OFFSET_LONG_ITEM + byteNum); for (int i = 0; i < byteNum; i++) { data[byteNum - i] = (byte) (srcData.length >>> (8 * i)); } System.arraycopy(srcData, 0, data, 1 + byteNum, srcData.length); return data; } }  static int decodeInt(byte[] data, int index); static BigInteger decodeBigInteger(byte[] data, int index); static RLPList decode2(byte[] msgData); static RLPElement decode2OneItem(byte[] msgData, int startPos); static DecodeResult decode(byte[] data, int pos); static byte[] encode(Object input); static byte[] encodeLength(int length, int offset); static byte[] encodeByte(byte singleByte); static byte[] encodeShort(short singleShort); static byte[] encodeInt(int singleInt); static byte[] encodeLong(long l); static byte[] encodeString(String srcString); static byte[] encodeBigInteger(BigInteger srcBigInteger); static byte[] encodeElement(byte[] srcData); static int calcElementPrefixSize(byte[] srcData); static byte[] encodeListHeader(int size); static byte[] encodeLongElementHeader(int length); static byte[] encodeList(byte[]... elements);  }### Answer:
@Test public void testEncodeElementOne() { byte[] actuals = encodeElement(new byte[] {0x01}); assertArrayEquals(new byte[] {(byte) 0x01}, actuals); }
@Test public void testEncodeElementNull() { byte[] actuals = encodeElement(null); assertArrayEquals(new byte[] {(byte) 0x80}, actuals); }
@Test public void testEncodeElementZero() { byte[] actuals = encodeElement(new byte[] {0x00}); assertArrayEquals(new byte[] {0x00}, actuals); }