Answer:
/*********************************************************************************
* (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.         *
*********************************************************************************/
public class Exercise_13_06 {
 /** Main method */
 public static void main(String[] args) {
  // Create two instances of ComparableCircle objects
  ComparableCircle comparableCircle1 = new ComparableCircle(12.5);
  ComparableCircle comparableCircle2 = new ComparableCircle(18.3);
  // Display comparableCircles
  System.out.println("\nComparableCircle1:");
  System.out.println(comparableCircle1);
  System.out.println("\nComparableCircle2:");
  System.out.println(comparableCircle2);
  // Find and display the larger of the two ComparableCircle objects
  System.out.println((comparableCircle1.compareTo(comparableCircle2) == 1  
  	? "\nComparableCircle1 " : "\nComparableCircle2 ") +  
  	"is the larger of the two Circles");
 }
}