code: private ProjectFile handleOleCompoundDocument(InputStream stream) throws Exception
     {
        POIFSFileSystem fs = new POIFSFileSystem(POIFSFileSystem.createNonClosingInputStream(stream));
        String fileFormat = MPPReader.getFileFormat(fs);
        if (fileFormat != null && fileFormat.startsWith("MSProject"))
        {
           MPPReader reader = new MPPReader();
           addListeners(reader);
           return reader.read(fs);
        }
        return null;
     }
docs: We have an OLE compound document... but is it an MPP file?
  
  @param stream file input stream
  @return ProjectFile instance