code: String addDefaultExtension(String filename) {
  		StringBuffer newFileName = new StringBuffer(filename);
  
  		String ext = "card";
  
  		newFileName.append("."); //$NON-NLS-1$
  		newFileName.append(ext);
  
  		return newFileName.toString();
  	}
docs: Adds default extension to the filename
  
  @param filename
  @return