question: public static byte [ ] encode ( InetAddress value ) { byte [ ] address = value . getAddress ( ) ; if ( address . length == 4 ) { byte [ ] mapped = new byte [ 16 ] ; System . arraycopy ( IPV4_PREFIX , 0 , mapped , 0 , IPV4_PREFIX . length ) ; System . arraycopy ( address , 0 , mapped , IPV4_PREFIX . length , address . length ) ; address = mapped ; } else if ( address . length != 16 ) { throw new UnsupportedOperationException ( "Only IPv4 and IPv6 addresses are supported" ) ; } return address ; }
target:  Encode InetAddress value into binary encoding 