code: public static void main(String[] args) {
  		CrawljaxConfigurationBuilder builder = CrawljaxConfiguration
  				.builderFor("http://demo.crawljax.com/");
  
  		// Add the invariant that checks that the string isn't present.
  		builder.crawlRules()
  				.addInvariant(
  						"Detect a string",
  						new NotRegexCondition(
  								"Invariants can be used to perform tests on the current state"));
  
  		// This plugin will just print the error.
  		builder.addPlugin(new OnInvariantViolationPlugin() {
  
  			@Override
  			public void onInvariantViolation(Invariant invariant,
  					CrawlerContext context) {
  				LOG.error("\n\n!!! Invariant {} violated !!!\n", invariant);
  			}
  
  		});
  
  		CrawljaxRunner crawljax = new CrawljaxRunner(builder.build());
  		crawljax.call();
  	}
docs: Run this method to start the crawl.