Chapter 6: Inheritance and Abstract Classes Chapter Topics 6.1 ...

CS151 Object-Oriented Design
Dr. Kim
{ protected void protetedMethod()
{ }
}
/* This doesn't compile.
class FinalSubclass extends FinalClass
{ }
*/
class ClassWithFinalMethods
{ public static final void staticFinalMethod()
{ }
}
class SubclassWithFinalMethods extends ClassWithFinalMethods
{ /* This doesn't compile.
public static void staticFinalMethod()
{ }
*/
}
6.3.3 Intent of using abstract classes
An abstract class is being used in a class hierarchy when we need a base class for two or more
actual classes that share some attributes and/or some behaviors. Consider the following example
to learn the use of abstract classes.
• The SceneShape Interface type that defines a number of operations that the shapes must
carry out.
public interface SceneShape
{
void setSelected(boolean b);
boolean isSelected();
void draw(Graphics2D g2);
void drawSelection(Graphics2D g2);
void translate(int dx, int dy);
boolean contains(Point2D aPoint);
}
• Abstract classes are convenient placeholders for factoring out common
behavior. Consider the following example to learn the use of abstract classes.
public class CarShape implements SceneShape
{ private boolean selected;
...
public void setSelected(boolean b) { selected = b; }
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