code: public static MappedByteBuffer map(File file, MapMode mode) throws IOException {
      checkNotNull(file);
      checkNotNull(mode);
      if (!file.exists()) {
        throw new FileNotFoundException(file.toString());
      }
      return map(file, mode, file.length());
    }
docs: Fully maps a file in to memory as per
  {@link FileChannel#map(java.nio.channels.FileChannel.MapMode, long, long)} using the requested
  {@link MapMode}.
  
  <p>Files are mapped from offset 0 to its length.
  
  <p>This only works for files <= {@link Integer#MAX_VALUE} bytes.
  
  @param file the file to map
  @param mode the mode to use when mapping {@code file}
  @return a buffer reflecting {@code file}
  @throws FileNotFoundException if the {@code file} does not exist
  @throws IOException if an I/O error occurs
  
  @see FileChannel#map(MapMode, long, long)
  @since 2.0