[...]
StyledText transcript = new StyledText(top, SWT.BORDER | SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
[...]
if (file != null && file.exists()) {		
  FileInputStream istream = new FileInputStream(file);
  if (istream == null) return;
  
  FileChannel fc = istream.getChannel();
  // Get the file's size and then map it into memory
  int sz = (int)fc.size();
  int cs = 0;
  final int piece = 5120 * 1024;		// read almost about 5 MB into cache
  while (cs < sz) {
     MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, cs, 
		(sz - cs) < piece ? (sz - cs) : piece);

     // Decode the file into a char buffer
    CharBuffer cb = decoder.decode(bb);							
   transcript.append(new String(cb.array()));
   transcript.redraw();							
   cs += piece;
  }
 fc.close();
 istream.close();