Fun with Swing - Learning Java Through Games - page 196

way of creating windows in this textbook. The reader, however, can easily modify the code
to use the event dispatch thread as the above code shows.
Next, let us concentrate on the BreakoutFrame class. A possible implementation is
shown next.

class BreakoutFrame extends JFrame {

public static final int HEIGHT = 600;

public static final int WIDTH = 488;

public static final int LOCATION X = 50;

public static final int LOCATION Y = 100;

public BreakoutFrame () {
setDefaultCloseOperation(JFrame.EXITON CLOSE) ;
setLocation(LOCATIONX, LOCATION Y) ;
setSize(WIDTH, HEIGHT);
setResizable( false );

}

}

Note that the first line of the constructor does not call the constructor of the super
class. Therefore, the empty constructor of the JFrame class is automatically called. As a
consequence, the above code is equivalent to the following code.

class BreakoutFrame extends JFrame {

public static final int HEIGHT = 600;

public static final int WIDTH = 488;

public static final int LOCATION X = 50;

public static final int LOCATION Y = 100;

public BreakoutFrame () {

super () ;
setDefaultCloseOperation(JFrame.EXITON CLOSE) ;
setLocation(LOCATIONX, LOCATION Y) ;
setSize(WIDTH, HEIGHT);
setResizable( false );

}

}

The actual window is created by the call super() . All the methods that are invoked in the
constructor (i.e., setDefaultCloseOperation , setLocation , setSize ,and setResizable )
belong to the JFrame class (or its superclasses). Since the BreakoutFrame classdoesnot
contain these methods, Java automatically searches for the methods in the JFrame super-
class.
The setDefaultCloseOperation method defines the behavior of the close button of
the window. There are four possible actions, which are specified by constants in the JFrame
class. The constant EXIT ON CLOSE means that the program will terminate when the window
is closed. The constant HIDE ON CLOSE means that the window will be hidden, but the
program will not terminate. If we want to display the window later, then we need to call
the setVisible method again. The constant DISPOSE ON CLOSE describes the behavior
where the window is destroyed, but the program is not terminated. Lastly, the constant
DO NOTHING ON CLOSE means that pressing the button that closes the window will have no
effect.
Before we explain how the setLocation and setSize methods work, let us first describe
the architecture of a computer screen. The screen of a computer is divided into pixels. The
actual resolution of the screen can be changed, where, for example, 1366 by 768 pixels is a