Lab Exercise 4: Tracing the Applet

CyberPetApplet inherits a number of methods from its superclasses. The main ones are

• start() is called once when the applet is started by the browser or appletviewer. This method calls init() and paint() automatically and then calls run() to get the applet running.
• run() is called by the start() method. It starts the applet running.
• stop() is called by the browser or appletviewer when the applet is quit.
• init() is called once when an applet starts up to perform any required initializations.
• paint() paints the graphics on the applet. It is called once when the applet starts and then it can be called by repaint() whenever the applet's appearance is changed. This is where you should place any drawing commands.

In addition to the above methods, which are inherited from Applet, our applets implement the ActionListener interface, so they also inherit the following method, which must be redefined in the applet.

• actionPerformed() is called automatically whenever one of the Buttons is clicked. It is passed information about the ActionEvent. This is where you should place commands that handle the applet's button clicks.

Of these methods, CyberPetApplet redefines init() and implements actionPerformed(). Definitions for the other methods don't appear in CyberPetApplet.

Place a System.out.println("In method X") statement, where X is the name of the method, in each method of both the CyberPetApplet and CyberPet classes. Run the program and note the output that it produces. Write down the order of execution of the statements in CyberPetApplet and CyberPet for various actions, such as clicking on the eat button or the sleep button.