1// initialize files form URIs and check paths/permissions
 2Path inputFile = Paths.get(inputFileName);
 3assert Files.exists(inputFile) == true;
 4assert Files.isReadable(inputFile) == true;
 5
 6Path outputFile = Paths.get(outputFileName);
 7assert Files.exists(outputFile.getParent()) == false;
 8assert Files.isWritable(outputFile.getParent()) == false;
 9
10// open file reader
11SeekableByteChannel inputChannel = Files.newByteChannel(inputFile);
12ByteBuffer byteBuffer = ByteBuffer.allocate(bufferSize);
13Charset charset = Charset.forName("US-ASCII");
14
15// open writer, overwrite target file if it exists
16Set options = new HashSet();
17options.add(StandardOpenOption.CREATE);
18options.add(StandardOpenOption.WRITE);
19FileChannel outputChannel = FileChannel.open(outputFile, options);
20
21// loop over channel
22while (inputChannel.read(byteBuffer) > 0) {
23    // flip for from input to output, then write to console
24    byteBuffer.flip();
25    System.out.print(charset.decode(byteBuffer));
26
27    // rewind so we can read buffer again from the beginning
28    // the write to file output channel
29    byteBuffer.rewind();
30    outputChannel.write(byteBuffer);
31
32    // flip channel from output to input again.
33    byteBuffer.flip();
34}
35outputChannel.close();