### Question:
DataWord implements Comparable<DataWord> { public DataWord mul(DataWord word) { BigInteger result = value().multiply(word.value()); return new DataWord(ByteUtil.copyToArray(result.and(MAX_VALUE))); } private  DataWord(byte[] data); static DataWord of(byte[] data); static DataWord of(ByteArrayWrapper wrappedData); @JsonCreator static DataWord of(String data); static DataWord of(byte num); static DataWord of(int num); static DataWord of(long num); byte[] getData(); byte[] getNoLeadZeroesData(); byte[] getLast20Bytes(); BigInteger value(); int intValue(); int intValueSafe(); long longValue(); long longValueSafe(); BigInteger sValue(); String bigIntValue(); boolean isZero(); boolean isNegative(); DataWord and(DataWord word); DataWord or(DataWord word); DataWord xor(DataWord word); DataWord negate(); DataWord bnot(); DataWord add(DataWord word); DataWord add2(DataWord word); DataWord mul(DataWord word); DataWord div(DataWord word); DataWord sDiv(DataWord word); DataWord sub(DataWord word); DataWord exp(DataWord word); DataWord mod(DataWord word); DataWord sMod(DataWord word); DataWord addmod(DataWord word1, DataWord word2); DataWord mulmod(DataWord word1, DataWord word2); DataWord shiftLeft(DataWord arg); DataWord shiftRight(DataWord arg); DataWord shiftRightSigned(DataWord arg); @JsonValue @Override String toString(); String toPrefixString(); String shortHex(); @Override boolean equals(Object o); @Override int hashCode(); @Override int compareTo(DataWord o); DataWord signExtend(byte k); int bytesOccupied(); boolean isHex(String hex); String asString(); static final int MAX_POW; static final BigInteger _2_256; static final BigInteger MAX_VALUE; static final DataWord ZERO; static final DataWord ONE; static final long MEM_SIZE; }### Answer:
@Test public void testMul() { byte[] one = new byte[32]; one[31] = 0x1; byte[] two = new byte[32]; two[11] = 0x1; DataWord x = DataWord.of(one); DataWord y = DataWord.of(two); x = x.mul(y); assertEquals(32, y.getData().length); assertEquals("0000000000000000000000010000000000000000000000000000000000000000", Hex.toHexString(y.getData())); }