How do you determine the ideal buffer size when using FileInputStream?

Question

I have a method that creates a MessageDigest (a hash) from a file, and I need to do this to a lot of files (>= 100,000). How big should I make the buffer used to read from t

Answer 1

In the ideal case we should have enough memory to read the file in one read operation. That would be the best performer because we let the system manage File System , allocation units and HDD at will. In practice you are fortunate to know the file sizes in advance, just use the average file size rounded up to 4K (default allocation unit on NTFS). And best of all : create a benchmark to test multiple options.