INHERITANCE AND POLYMORPHISM - Introduction to Java Programming: Comprehensive Version - page 414

This is wrong, because the private data fields color and filled in the GeometricObject
class cannot be accessed in any class other than in the GeometricObject class itself. The
only way to read and modify color and filled is through their getter and setter methods.
The Rectangle class (Listing 11.3) extends the GeometricObject class (Listing 11.1)
using the following syntax:

Subclass

Superclass

public class Rectangle extends GeometricObject

The keyword extends (lines 1-2) tells the compiler that the Rectangle class extends the
GeometricObject class, thus inheriting the methods getColor , setColor , isFilled ,
setFilled , and toString .

L ISTING 11.3

RectangleFromSimpleGeometricObject.java
1 public class RectangleFromSimpleGeometricObject
2 extends SimpleGeometricObject { extends superclass

data fields 3 private double width;

4 private double height;

5
6 public RectangleFromSimpleGeometricObject() {
7 }
8
9

constructor

public RectangleFromSimpleGeometricObject(

10 double width, double height) {

11 this .width = width;

12 this .height = height;

13 }
14
15 public RectangleFromSimpleGeometricObject(
16 double width, double height, String color, boolean filled) {
17 this .width = width;
18 this .height = height;
19 setColor(color);
20 setFilled(filled);
21 }
22
23 /** Return width */

24 public double getWidth() { methods

25 return width;

26 }
27
28

/** Set a new width */

29 public void setWidth( double width) {

30 this .width = width;

31 }
32
33 /** Return height */

34 public double getHeight() {

35 return height;

36 }
37
38

/** Set a new height */

39 public void setHeight( double height) {

40 this .height = height;

41 }