So some investigation into the applet lifecycles reveals that:
the class file is loaded into the browser only once and the init() method is called only once. after that, if you move to some other application, then the applet's stop method is called. When you come to the page again, the start method of the applet is called by the browser. the destroy method is called only once i.e. when you close the browser (and all all windows of that browser), then the java class file is not removed from the working memory of the browser.