Java Reference
In-Depth Information
public
RectangleProgram()
{
setTitle("Area and Perimeter of a Rectangle");
setSize(400, 300);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(
true
);
}
You could create a window by using an object of type
JFrame
. However, for our
program, if we do so, then the window created will not have a title or the required size
unless we specify the necessary statements similar to the ones in the preceding code.
Because
RectangleProgram
is also a
class
, we can create objects of type
RectangleProgram
. Because the
class
RectangleProgram
extends
the definition
of the
class
JFrame
, it inherits the properties of the
class
JFrame
.Ifwecreateanobjectof
type
RectangleProgram
, not only do we create a window, but the created window will also
have a title and a specific size, and the window will be displayed when the program executes.
Consider the following statement:
RectangleProgram rectObject =
new
RectangleProgram();
//Line 5
This statement creates the object
rectObject
of type
RectangleProgram
.
The statement in Line 5 causes the window shown in Figure 6-4 to appear on the screen.
FIGURE 6-4
Window with the title
Area and Perimeter of a Rectangle
You can close the window in Figure 6-4 by clicking the ''close'' button, the button
containing the
, in the upper-right corner. The window in Figure 6-4 is empty because
we have not yet created labels, text fields, and so on.
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