ABSTRACT CLASSES AND INTERFACES - Introduction to Java Programming - page 593

Sections 15.4-15.8
*15.7

( Enable GeometricObject comparable ) Modify the GeometricObject
class to implement the Comparable interface, and define a static max method
in the GeometricObject class for finding the larger of two
GeometricObject objects. Draw the UML diagram and implement the new
GeometricObject class. Write a test program that uses the max method to find
the larger of two circles and the larger of two rectangles.

*15.8

( The ComparableCircle class ) Define a class named ComparableCircle
that extends Circle and implements Comparable . Draw the UML diagram and
implement the compareTo method to compare the circles on the basis of area.
Write a test class to find the larger of two instances of ComparableCircle
objects.

*15.9

( The Colorable interface ) Design an interface named Colorable with a
void method named howToColor() . Every class of a colorable object must
implement the Colorable interface. Design a class named Square that
extends GeometricObject and implements Colorable . Implement
howToColor to display the message Color all four sides .
Draw a UML diagram that involves Colorable , Square , and
GeometricObject . Write a test program that creates an array of five
GeometricObject s. For each object in the array, invoke its howToColor
method if it is colorable.

*15.10

( Revise the MyStack class ) Rewrite the MyStack class in Listing 11.9 to per-
form a deep copy of the list field.

*15.11

( Enable Circle comparable ) Rewrite the Circle class in Listing 15.2 to
extend GeometricObject and implement the Comparable interface. Over-
ride the equals method in the Object class. Two Circle objects are equal if
their radii are the same. Draw the UML diagram that involves Circle ,
GeometricObject , and Comparable .

*15.12

( Enable Rectangle comparable ) Rewrite the Rectangle class in Listing 15.3
to extend GeometricObject and implement the Comparable interface. Over-
ride the equals method in the Object class. Two Rectangle objects are
equal if their areas are the same. Draw the UML diagram that involves
Rectangle , GeometricObject , and Comparable .

VideoNote

Redesign the Rectangle
class

*15.13

( The Octagon class ) Write a class named Octagon that extends
GeometricObject and implements the Comparable and Cloneable inter-
faces. Assume that all eight sides of the octagon are of equal size. The area can
be computed using the following formula:

area = (2 + 4/ 2 2) * side * side

Draw the UML diagram that involves Octagon , GeometricObject ,
Comparable , and Cloneable . Write a test program that creates an Octagon
object with side value 5 and displays its area and perimeter. Create a new object
using the clone method and compare the two objects using the compareTo
method.

*15.14

( Sum the areas of geometric objects ) Write a method that sums the areas of all
the geometric objects in an array. The method signature is:

public static double sumArea(GeometricObject[] a)
Write a test program that creates an array of four objects (two circles and two
rectangles) and computes their total area using the sumArea method.