docs: @Pure
  	public static boolean hasExtension(File filename, String extension) {
  		if (filename == null) {
  			return false;
  		}
  		assert extension != null;
  		String extent = extension;
  		if (!"".equals(extent) && !extent.startsWith(EXTENSION_SEPARATOR)) { //$NON-NLS-1$
  			extent = EXTENSION_SEPARATOR + extent;
  		}
  		final String ext = extension(filename);
  		if (ext == null) {
  			return false;
  		}
  		if (isCaseSensitiveFilenameSystem()) {
  			return ext.equals(extent);
  		}
  		return ext.equalsIgnoreCase(extent);
  	}