// reading a file with memoryMapping
File file = new File( "somebytes.dat" );

fis = new FileInputStream( file );

FileChannel fc = fis.getChannel();

MappedByteBuffer bb = fc.map( FileChannel.MapMode.READ_ONLY, 0, file.length() );

// bb.flip();  // not needed

int limit = bb.limit(); // bytes in buffer
for ( int offset=0; offset<limit; offset++ )
   {
   byte b = bb.get( offset );
   out.println( b );
   }