code: public static Iterator<ImageReader> getImageReadersBySuffix(String fileSuffix) {
  		if (fileSuffix == null) {
  			throw new IllegalArgumentException("fileSuffix == null!");
  		}
  		// Ensure category is present
  		Iterator iter;
  		try {
  			iter = theRegistry.getServiceProviders(ImageReaderSpi.class, new ContainsFilter(readerFileSuffixesMethod, fileSuffix), true);
  		} catch (IllegalArgumentException e) {
  			return new HashSet().iterator();
  		}
  		return new ImageReaderIterator(iter);
  	}
docs: Returns an <code>Iterator</code> containing all currently registered <code>ImageReader</code>s that
  claim to be able to decode files with the given suffix.
  
  @param fileSuffix
  a <code>String</code> containing a file suffix (<i>e.g.</i>, "jpg" or "tiff").
  
  @return an <code>Iterator</code> containing <code>ImageReader</code>s.
  
  @exception IllegalArgumentException
  if <code>fileSuffix</code> is <code>null</code>.
  
  @see javax.imageio.spi.ImageReaderSpi#getFileSuffixes