Returns a byte array containing the two's-complement
representation of this BigInteger. The byte array will be in
big-endian byte-order: the most significant byte is in
the zeroth element. The array will contain the minimum number
of bytes required to represent this BigInteger, including at
least one sign bit, which is (ceil((this.bitLength() +
1)/8)). (This representation is compatible with the
(byte[]) constructor.)
BigInteger(byte[])
Diagram: BigInteger, BigDecimal