Use Java NIO to copy file

private void copyFile(String source, String destination) throws IOException {
        FileInputStream fis = new FileInputStream(source);
        FileChannel fci = fis.getChannel();
        
        FileOutputStream fos = new FileOutputStream(destination);
        FileChannel fco = fos.getChannel();
        
        // create a buffer with 2048 size for buffering data
        ByteBuffer buffer = ByteBuffer.allocate(2048);
        int b = fci.read(buffer);
        while(b != -1) { // reach the end of the channel?
            
            // flip the buffer
            buffer.flip();
            
            // write to the destination channel
            fco.write(buffer);
            
            // clear the buffer and use it for the next read process
            buffer.clear();
            
            // read a block of data and put it in the buffer
            b = fci.read(buffer);
        }
        
        fis.close();
        fos.close();        
    }