private HyperlinkEvent validateURL(HyperlinkEvent event) {
		URL url = event.getURL();
		if (url == null) {
			Msg.trace(this, "No URL for link: " + event);
			return maybeCreateNewHyperlinkEventWithUpdatedURL(event);
		}
		try {
			url.openStream();// assume that this will fail if the file does not exist
		}
		catch (IOException ioe) {
			// assume this means that the url is invalid
			Msg.trace(this, "URL of link is invalid: " + url.toExternalForm());
			return maybeCreateNewHyperlinkEventWithUpdatedURL(event);
		}

		return event;// url is fine
	}
Tests the URL of the given event.  If the URL is invalid, a new event may be created if
 a new, valid URL can be created. Creates a new event with a patched URL if
 the given event's URL is invalid.
Ghidra/Framework/Help/src/main/java/help/GHelpHTMLEditorKit.java