Java Reference
In-Depth Information
Initially, you define the five classes shown
Figure 19-22
that represent shapes, with the
Element
class as
a base. They provide objects that represent straight lines, rectangles, circles, freehand curves, and blocks of
text. These classes inherit the fields that you define for the
Element
class and they are serializable.
As you can see from the names of the Sketcher shape classes in
Figure 19-22
,
they are all nested classes
to the
Element
class. The
Element
class serves as the base class, as well as housing the shape classes. This
helps to avoid any possible confusion with other classes in the Java libraries that might have the same names.
Because there are no
Element
objects around, you declare the inner shape classes as static members of the
Element
class.
You can now define the base class,
Element
. This won't be the final version because you will add more
functionality in later chapters. Here's the code for
Element.java
:
import java.awt.*;
import java.io.Serializable;
public abstract class Element implements Serializable {
protected Element(Point position, Color color) {
this.position = position;
this.color = color;
}
public Color getColor() {
return color;
}
public Point getPosition() {
return position;
}
public java.awt.Rectangle getBounds() {
return bounds;
}
public abstract void draw(Graphics2D g2D);
public abstract void modify(Point start, Point last);
protected Point position;
// Position of a shape
protected Color color;
// Color of a shape
protected java.awt.Rectangle bounds;
// Bounding rectangle
private final static long serialVersionUID = 1001L;
}
Directory "Sketcher 4 drawing sketch line and rectangle elements"
Put this file in the same directory as
Sketcher.java
. You have defined a constructor to initialize the
color
and
position
data member and the
get
methods to provide access to these. The
bounds
member is
created by the subclasses and it also has a
get
method. The member and return type must be qualified by the
