Menu
When I am using FileInputStream to read an object (say a few bytes), does the underlying operation involve:
1) Reading a whole block of disk so that if I subsequently do another read operation, it wouldnt require a real disk read as that portion of the file was already fetched in the last read operation?
OR
2) A new disk access to take place because FileInputStream does not do any buffering and bufferedInputStream should have been used instead to achieve the effect of (1)?
I think that since the FileInputStream uses the read system call and it reads only a set of pages from hard disk, some buffering must be take place.
563
BufferedInputStream is buffered, but FileInputStream is not.
Java FileInputStream class obtains input bytes from a file. It is used for reading byte-oriented data (streams of raw bytes) such as image data, audio, video etc. You can also read character-stream data. But, for reading streams of characters, it is recommended to use FileReader class.
With a BufferedInputStream , the method delegates to an overloaded read() method that reads 8192 amount of bytes and buffers them until they are needed. It still returns only the single byte (but keeps the others in reserve). This way the BufferedInputStream makes less native calls to the OS to read from the file.
The read() method of a FileInputStream returns an int which contains the byte value of the byte read. If the read() method returns -1, there is no more data to read in the stream, and it can be closed. That is, -1 as int value, not -1 as byte value.
FileInputStream will make an underlying native system call. Most OSes will do their own buffering for this. So it does not need a real disk seek for each byte. But still, you have the cost of making the native OS call, which is expensive. So BufferedStream would be preferable. However, for reading small amounts of data (like you say, a few bytes or even kBs), either one should be fine as the number of OS calls won't be that different.
131
Native code for FileInputStream is here: it doesn't look like there is any buffering going on in there. The OS buffering may kick in, but there's no explicit indicator one way or another if/when that happens.
40
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
