code: public final void addExtension(final String extension) {
  		if (filters == null) {
  			filters = new HashMap<>(1);
  		}
  
  		filters.put(extension.toLowerCase(Locale.getDefault()), this);
  		fullDescription = null;
  	}
docs: Adds a filetype "dot" extension to filter against.
  
  For example: the following code will create a filter that filters out all files except those that end in ".jpg" and ".tif":
  
  MExtensionFileFilter filter = new MExtensionFileFilter(); filter.addExtension("jpg"); filter.addExtension("tif");
  
  Note that the "." before the extension is not needed and will be ignored.
  
  @param extension
  String