guava/src/com/google/common/io/Files.java
@Beta
  public static MappedByteBuffer map(File file) throws IOException {
    checkNotNull(file);
    return map(file, MapMode.READ_ONLY);
  }
@Beta
  public static MappedByteBuffer map(File file) throws IOException {
    checkNotNull(file);
    return map(file, MapMode.READ_ONLY);
  }
Fully maps a file read-only in to memory as per {@link
FileChannel#map(java.nio.channels.FileChannel.MapMode, long, long)}.

<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
@return a read-only 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