Appending to an array vs writing to file

Question

I'm writing a program which takes in a byte array of potentially millions of bytes, reads each one from a ByteArrayInputStream, and if the byte is not "printable" (ascii 32-126), that byte is encoded in a certain way and written to a ByteArrayOutputStream instance; if the byte is "printable" it is directly written to that same ByteArrayOutputStream instance. So from a broader view I am taking in a byte array, and getting back a similar byte array except certain characters have been encoded.

My question is: would it be faster to write my data out to a file or to continuously be writing to this OutputStream?

Answer 1

It will be faster to write the data to your output stream. Writing to a file will involve disk access, which is slower than access to the RAM where the byte array inside the ByteArrayOutputStream lives.

However, if you eventually want to write your byte array out to some other place (say a file) then the intermediate step of the ByteArrayOutputStream is unnecessary and you should just write straight to the end destination e.g. FileOutputStream.