Question

The following code doesn’t work to download a file (btw clen is file’s length):

    int pos = 0, total_pos = 0;
    byte[] buffer = new byte[BUFFER_SIZE];
            while (pos != -1) {
                pos = in.read(buffer, 0, BUFFER_SIZE);
                total_pos += pos;
                out.write(buffer);
                setProgress((int) (total_pos * 100 / clen));
            }

…but this works fine:

    int buf;
    while ((buf = in.read()) != -1)
        out.write(buf);

I’m wondering why, even though the second code segment works quickly. On that note, is there any particular reason to use a byte[] buffer (since it doesn’t seem to be faster, and BufferedInputStream already uses a buffer of its own….?)

Answer 1

Here’s how it should be done.

public static void copyStream(InputStream is, OutputStream os)
    {
        byte[] buff = new byte[4096];
        int count;
        try {
            while((count = is.read(buff)) > 0)
                os.write(buff, 0, count);

        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if(is != null)
                    is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if(os != null)
                    os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }