Android file copy

Question

I am finding that reading one line at a time from a text file on the SD card is rather slow. I imagine that it might be quicker if the file is in internal memory, so I want

Answer 1

One of the truisims of CS that only becomes more true with time as CPUs get faster is: I/O is slow.

If you want speed, generally your best bet is to do as few I/O's as possible. Ideally, find out how big that file is, allocate that much memory, and then read the entire thing in one big I/O. Then you can just access the data from program memory. If you might not have enough RAM for every concievable file size then you might have to do a bit more work, but this is what you should strive for.

Answer 2

If you are pulling the file in for use in your application what I suggest you do is read in the data then stuff the in memory data you have collected into some kind of reader (BufferedReader perhaps) so that you can then read the lines from there.

Here is an example of what I typically do:

// Assumption: I already have the file object I want to read
// Note: I'm not doing any error handling.
InputStream input = new FileInputStream(file);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int bytesRead = 0;
while( (bytesRead = input.read(buffer)) > 0){
    baos.write(buffer, 0, bytesRead);
}
StringReader stringReader = new StringReader( new String(baos.toByteArray()) );
BufferedReader bufferedReader = new BufferedReader( stringReader );
for(String line : bufferedReader.readLine()){
    // TODO: Handle each line appropriately or something
    Log.d("Reading Data Example", line);
}