Yes, generally very easily. For many applets, you can just say
JFrame frame = new JFrame(); JApplet applet = new TheAppletClass(); frame.getContentPane().add(applet); frame.setSize(600, 600); frame.setVisible(true); applet.init(); frame.validate(); applet.start();
Some applets (but not all) use applet-specific facilities like applet parameters, the AudioClip sound API, etc. These applets will need some small changes -- but generally nothing too major, just a small matter of coding.