UGC-NET Computer Science JAVA Questions with Explanation

Q : 1 Which method is called first by an applet program ?

(A) start( )

(B) run( )
(C) init( )

(D) begin( )

(UGC-NET December 2014 Paper 3)

Answer: (C) init()

Explanation:

Applet Life Cycle

When an applet begins, the AWT calls the following methods, in this sequence:
1. init( )
2. start( )
3. paint( )

When an applet is terminated, the following sequence of method calls takes place:
1. stop( )
2. destroy( )

1. init( )

The init( ) method is the first method to be called. This is where you should initialize variables. This method is called only once during the run time of your applet.

2. start( )

The start( ) method is called after init( ). It is also called to restart an applet after it has been stopped. Whereas init( ) is called once—the first time an applet is loaded—start( ) is called each time an applet’s HTML document is displayed onscreen. So, if a user leaves a web page and comes back, the applet resumes execution at start( ).

3. paint( )

The paint( ) method is called each time your applet’s output must be redrawn. This situation can occur for several reasons. For example, the window in which the applet is running may be overwritten by another window and then uncovered. Or the applet window may be minimized and then restored. paint( ) is also called when the applet begins execution. Whatever the cause, whenever the applet must redraw its output, paint( ) is called. The paint( ) method has one parameter of type Graphics. This parameter will contain the graphics context, which describes the graphics environment in which the applet is running. This context is used whenever output to the applet is required.

4. stop( )

The stop( ) method is called when a web browser leaves the HTML document containing the applet—when it goes to another page, for example. When stop( ) is called, the applet is probably running. You should use stop( ) to suspend threads that don’t need to run when the applet is not visible. You can restart them when start( ) is called if the user returns to the page.

5. destroy( )

The destroy( ) method is called when the environment determines that your applet needs to be removed completely from memory. At this point, you should free up any resources the applet may be using. The stop( ) method is always called before destroy( ).

In some situations, your applet may need to override another method defined by the AWT, called update( ). This method is called when your applet has requested that a portion of its window be redrawn. The default version of update( ) first fills an applet with the default background color and then calls paint( ). If you fill the background using a different color in paint( ), the user will experience a flash of the default background each time update( ) is called—that is, whenever the window is repainted. One way to avoid this problem is to override the update( ) method so that it performs all necessary display activities. Then have paint( ) simply call update( ).