title: difference between the methods update() and dofinal() in cipher
body: <p>I have read one article  about difference between the methods update() and dofinal() in cipher. 
   It was about what will happend if we want to encrypt 4 Bytes Array, when the block size of the cipher is for example 8 Bytes. If we call update here it will return null. My question is: what will happen if we call doFinal() with a 4 byte array to encrypt, and the buffer size is 8 bytes, how many bytes encoded data will we receive on the return?</p>