Java function/method

i communicate with a PIC micro controller through serial.. i send a command to it. and it starts sending me contents of memory. i need a function which will read the incoming stream from serial.. it may take some minutes to receive all.. 32Mbits memory.. 4 mb of data.. over serial 256k baud rate.. so it will read incoming data.. and store it in a stream variable.. data format is 512 bytes data + 32 bytes tail.. + 512 bytes data + 32 bytes tail.. so i need to devide all data in an array or arrayliost or a arraystream.. and i need to collect all tails in another aray... etc.. so one array will be 512 bytes + 512 bytes+ 512 bytes other array will be 32 bytes + 32 bytes + 32 bytes ... at the end we will write these info into a file ------------------------------- So in brief function reads incoming stream from serial.. store it in 2 separate arrays .. and writes the first array to file. and then writes the second array to file